FW Handout 10

BIBC 102 TA : WEBSTER FRANCOIS SECTION: A02 MON 11-150a CENTER 217B OH: THURS. 6-7PM YORK 3010B EMAIL: [email protected]

HANDOUT # 10

I. Fill in all of the enzyme catalyzed reactions which convert the substrate on the left to the product on

the right. Draw the correct structure for each intermediate molecule. Include the names or abbreviations of any other reactants and products (e.g., ATP, ADP, Pi, NAD+, NADH, etc.), and any required prosthetic groups (e.g., TPP, FAD, biotin, etc.).

A. acetyl CoA (cytosol)

CH3CH2CH2(C=O)–SAC B. Pyruvate in matrix (gluconeogenesis in liver) Phosphoenolpyruvate _____________________________________________________________________________________ C. Dihydroxyacetone phosphate (gluconeogenesis in liver) Glucose --------------------------------------------------------------------------------------------------------------------------------- D. Acetyl CoA (matrix)

Acetyl CoA (cytosol) E. Oxaloacetate (cytosol) Oxaloacetate (matrix)(assume Phosphoenolpyruvate carboxy- Kinase is inactive) ______________________________________________________________________________________

__ F. Glucose Glycogen (indicate the point on the structure of the polymer where the entering glucose attaches)

II. Outline the steps starting with an increase in adenylate cyclase activity in the liver on the left and

ending with the relevant responses indicated below on the right. Use arrows ( or ↓)to show the effect at each step, as in the lecture handout.

(A) Changes in the activities of Glycogenolysis and Glycogen Synthesis (liver) (B) Changes in the activities of Gluconeogenesis and Glycolysis (liver)

III. (A) based on your fundamental understanding of biological oxidations and reductions, estimate how many oxygen atoms will be consumed in the aerobic oxidation of histidine. Approximately how many ATPs will be formed? Show your calculations for credit.

(B) The catabolism of histidine, like that of most amino acids, has been designed so that it can support a process important to survival during starvation, a process that fatty acids cannot sustain. What is this design feature, and how does it help in survival during starvation? Why can't fatty acids support this process? IV. Multiple Choice.

1. Inside adipose cells, the ∆G′ for the hydrolysis of ATP to ADP and Pi is about -48 kJ/mole. Given that the ∆G°′ for ATP hydrolysis to ADP and Pi is –30.5 kJ/mol and RT = 2.48 kJ/mol, what is the approximate ratio of [ATP] to [ADP][Pi] in these cells? Choose the most nearly correct answer.

(A) 5000/1 (B) 4000/1 (C) 2000/1 (D) 1000/1 (E) 500/1 2. What will be the net number of ATP equivalents produced when one glucose subunit of muscle

glycogen is converted to lactate under anaerobic conditions in a muscle cell? (A) 1 (B) 2 (C) 3 (D) 4 (E) 0 3. Which carbon atom(s) of the products ethanol and CO2 will be labeled when a yeast cell extract is

incubated anaerobically with glucose-1,5-14C? The carbons of ethanol are numbered: CH3 CH2OH (A) In C1 but not in C2 or CO2 (D) In C2 and CO2 but not in C1 (B) In C2 but not in C1 or CO2 (E) All 14C will be lost as 14CO2

(C) In C1 and C2 but not in CO2 4. Which carbon(s) of glucose will be labeled most rapidly when a short pulse of 14CO2 is added to plant

cells that are actively carrying out photosynthesis? (A) C1 and C5 (B) C2 and C6 (C) C1 and C6 (D) C2 and C5 (E) C3 and C4 5. A muscle cell is actively engaged in the complete aerobic catabolism of glucose subunits of its

intracellular glycogen to 6CO2. What will be the net yield of ATP equivalents (i.e., ATP, GTP, UTP, etc.) from each glucose subunit when excess DNP is present?

(A) 5 (B) 4 (C) 3 (D) 2 (E) No ATP can be produced 6. When a cell extract containing all of the enzymes of glycolysis and the TCA cycle is incubated

aerobically with glucose-1-14C, what fraction of the original label will remain in oxaloacetate after two turns of the TCA cycle? [In this problem, assume that all label enters the cycle in the first citrate synthase step, and that the acetyl CoA entering in the second turn of the TCA cycle is unlabeled.]

(A) 0% (B) 25% (C) 50% (D) 75% (E) 100% 7. The respiratory quotient (ratio of CO2 generated/O2 consumed) is 1.00 for glucose. What is the

respiratory quotient for the C18 saturated fatty acid stearate? Circle the most nearly correct value . (A) 1.00 (B) 0.90 (C) 0.80 (D) 0.75 (E) 0.70

8. One micromole of a fully tritiated, 16-carbon, straight-chain, saturated fatty acid C3H3(C3H2)14COO3H

is added to a preparation of disrupted mitochondria, which degrades it completely to acetyl CoA. If the 8 micromoles of product are re-isolated from the reaction mixture, hydrolyzed to free acetate, and assayed for radioactivity, what will be their overall tritium-to-carbon ratio (i.e., 3H : C)?

(A) 2 : 3 (B) 3 : 8 (C) 1 : 2 (D) 5 : 8 (E) 1 : 1 9. The following graph represents the hypothetical results of an experiment in which the amount of O2

consumed is measured over a time interval during which intact mitochondria are treated sequentially with five substances. The identity of these 5 substances can be inferred from their effect on the amount of O2 consumed. Assume that Pi and an abundant source of matrix NADH are present.

(A) 1 = Arsenate 2 = Oligomycin 3 = DNP 4 = Antimycin A 5 = Succinate (B) 1 = ADP 2 = Oligomycin 3 = Arsenate 4 = Cyanide 5 = DNP (C) 1 = ADP 2 = Oligomycin 3 = DNP 4 = Rotenone 5 = Glycerol P (D) 1 = DNP 2 = Rotenone 3 = Succinate 4 = Cyanide 5 = Arsenate (E) 1 = ADP 2 = Atractyloside 3 = DNP 4 = Oligomycin 5 = Arsenate 10. What will be the exact net number of ATP equivalents produced when palmitate is completely

oxidized to 16 CO2 under aerobic conditions? Assume that palmitate is initially present in the cytosol of the cell.

(A) 138 (B) 136 (C) 134 (D) 131 (E) 129 11. Which carbon atoms in palmitate will be labeled most rapidly when a cell extract is given the

following substrates? Assume that acetyl CoA carboxylase is absent. CH3C SCoA + excess O2C-CH2-14C SCoa

(A) All even numbered carbon atoms in palmitate will be labeled. (B) All odd numbered carbon atoms in palmitate will be labeled. (C) Carbons 1, 3, 5, 7, 9, 11, and 13 in palmitate will be labeled. (D) Carbons 2, 4, 6, 8, 10, 12, and 14 in palmitate will be labeled. (E) Only carbon 1 in palmitate will be labeled.

12. Starting with 2 lactate molecules, the number of ATP equivalents required for the synthesis of 1 glucose subunit of glycogen in the liver is (A) 3 (B) 4 (C) 5 (D) 6 (E) 7

13. A cell extract containing all of the enzymes of glycolysis is incubated with 32P labeled ATP (i.e.,

Adenosine - P - P - 32 P). Assuming that all of the glucose used in the cell during the experiment is derived from blood glucose and that inorganic phosphate is unlabeled, which of the following labeled compounds would be formed? Assume pyruvate kinase is inactivated.

1. Glucose-6-32P 3. 132P, 632P-Fructose bisphosphate 2. 3-32P-phosphoglycerate 4. 132P, 332P-Bisphosphoglycerate

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All 14. How many deuterium atoms will be incorporated into palmitate starting with the following

compounds? Assume that acetyl CoA carboxylase is absent. CH3(C=O)SCoA + excess O2CCD2(C=O)SCoA (A) 7 (B) 10 (C) 14 (D) 16 (E) 17

15. Which one of the following statements is blatantly false?

(A) 14C label will enter glucose if a fasting animal is given aspartate uniformly labeled with 14C. (B) No 14C label will enter glucose if a fasting animal is given palmitate uniformly labeled with 14C. (C) One of the major metabolic adjustments to a fast is the change in the major fuel of the brain

from glucose to ketone bodies. (D) After one day of a fast, the major source of blood glucose is gluconeogenesis from amino acid

precursors. (E) Most energy in animals is stored as triacylglycerols rather than as glycogen because animals

need to minimize the weight they need to carry in order to store a given amount of energy. 16. Which one of the following statements is blatantly false?

(A) (A) Carbon dioxide is essential for fatty acid biosynthesis. (B) (B) Carbon dioxide is essential for gluconeogenesis starting with pyruvate. (C) (C) Carbon dioxide is essential for the net synthesis of TCA intermediates from glucose ("net

synthesis" means an increase in the sum total of all TCA cycle intermediates). (D) (D) 14C label in carbon dioxide cannot, by the reactions we have studied, enter fatty acids. (E) (E) 14C label in carbon dioxide can, by the reactions we have studied, enter glucose during

gluconeogenesis. 17. Which one of the following statements is blatantly false?

(A) (A) All of the 12 NADPH molecules consumed in the fixation of 6 CO2 molecules to form one glucose molecule are used in the glyceraldehyde-3-P dehydrogenase step.

(B) (B) Starting with glucose-6- P , only one ATP equivalent is required to synthesize a glucose subunit of glycogen.

(C) (C) 12 of the 18 ATP molecules consumed in the fixation of 6 CO2 to glucose are used in the 3-phosphoglycerate kinase step.

(D) (D) Starting with two molecules of phosphoenol pyruvate, 4 ATP equivalents and 2 NADH molecules are required to synthesize free glucose.

(E) Phosphoglucomutase, the enzyme that interconverts G1P and G6P, is required for liver cells to incorporate glucose into glycogen and to break liver glycogen down to generate free glucose.

18. Which one of the following statements about regulation in liver cells is blatantly false?

(A) (A) A decrease in blood glucose will increase adenylate cyclase activity in liver cells. (B) (B) A decrease in fructose-2,6-BP levels will increase the rate of gluconeogenesis in liver cells. (C) (C) An increase in glucagon levels in the blood will increase the activity of glycogen

phosphorylase in liver cells. (D) (D) When phosphofructokinase II activity decreases, the fructose bisphosphatase I activity

increases in liver cells. (E) (E) Protein kinase phosphorylates and thereby inactivates fructose bisphosphatase II in liver

cells. 19. Which one of the following statements is blatantly false?

(A) (A) Humans cannot synthesize a fatty acid with a carbon-carbon double bond in a position greater than C9 = C10.

(B) (B) Carnitine acyl transferase I (CAT I) is allosterically inhibited by malonyl CoA. (C) (C) Aspirin irreversibly inhibits prostaglandin synthase by acetylating a serine residue in the

enzyme. (D) (D) In fatty acid oxidation, the formation of palmitoyl CoA from palmitate occurs in the cytosol

and is driven by the hydrolysis of ATP to AMP plus pyrophosphate. (E) (E) The acetyl CoA used for fatty acid biosynthesis travels from the matrix to the cytosol by the

facilitated diffusion of acetyl CoA across the inner mitochondrial membrane. 20. Which one of the following statements is blatantly false?

(A) (A) 14 NADPH molecules are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

(B) (B) 7 ATP equivalents are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

(C) (C) Protein kinase phosphorylates and thereby activates acetyl CoA carboxylase.

(D) (D) The fatty acid synthase complex cannot synthesize fatty acids longer than CH3(CH2)14CO2H. (E) (E) Carbon dioxide is absolutely required for the synthesis of stearyl CoA (stearate is a C18

saturated fatty acid) starting with palmitoyl CoA and acetyl CoA. 21. Which one of the following statements is blatantly false?

(A) At the steady state mass action ratio of [ATP]/[ADP][Pi] in a typical cell cytosol, the coupled hydrolysis of both high energy bonds of ATP will increase the ratio of product to substrate in a biosynthetic reaction by 1016.

(B) The steady state ratio of NADPH to NADP+ is maintained at a far greater value than the ratio of NADH to NAD+ in order to enable NADPH to better drive reductions in biosynthesis.

(C) In a typical muscle cell, the reaction catalyzed by phosphofructokinase has a higher ratio of reactants to products than would be expected from the equilibrium constant for this reaction.

(D) Catabolic reaction pathways are inhibited by a high ratio of [ATP]/[ADP][Pi] and activated by a low ratio of [ATP]/[ADP][Pi].

(E) At steady state in a cell, all reactions in glycolysis which are not under allosteric regulation have a standard free energy change (∆G°′) of approximately zero.


(A) Glucose-6-phosphatase is not found in muscle cells. (B) Urea is formed only in liver cells. (C) The formation of acetoacetyl CoA from acetoacetate and succinyl CoA always occurs in liver

cells. (D) In a well fed non-diabetic individual, the brain does not derive energy from ketone bodies. (E) Ketone bodies are synthesized only by liver cells.

23. Which one of the following enzymes is not located in the mitochondrial matrix? (A) Pyruvate carboxylase (D) HMG CoA Reductase (B) α-ketoglutarate dehydrogenase (E) Isocitrate dehydrogenase (C) the thiolase reaction of fatty acid oxidation

24. You are studying catabolism and electron transport in a minced tissue preparation of pigeon breast

muscle which contains all of the enzymes of glycolysis and intact mitochondria. You already know that this tissue is capable of perfectly normal aerobic and anerobic glycolysis. Furthermore the TCA cycle and electron transport can all function normally. Now in the presence of O2 and glucose, you add an inhibitor of electron transport to the aerobically respiring tissue. Which one of the following possible results are you least likely to see? (A) O2 consumption falls dramatically. (B) The NADH/NAD+ ratio in the mitochondria increases. (C) All CO2 production from glucose ceases. (D) All ATP synthesis from glucose ceases. (E) The rate of glucose consumption increases.

25. When O2 is added to a suspension of yeast cells which have been growing anaerobically on glucose,

the rate of glucose consumption falls dramatically and ethanol ceases to be produced. Which one of the following statements about this effect, called the Pasteur effect, is blatantly false? (A) The concentration of NADH in the mitochondrial matrix will increase when O2 is added. (B) The phosphofructokinase reaction will be inhibited by higher ATP levels when O2 is added. (C) Assuming ATP needs are constant, the theoretical decrease in glucose consumption when O2 is

added is 18-fold. (D) Assuming ATP needs are constant, the rate of CO2 evolution will decrease when O2 is added. (E) The ratio of [ATP]/[ADP][Pi] will increase when O2 is added.

26. Which one of the following statements is most blatantly false? (A) Antimycin A blocks photosynthetic electron transport at the cytochrome bf complex. (B) DNP allows free diffusion of H+ across the thylakoid membrane and thereby prevents ATP

synthesis. (C) Dihydrofolate is produced in the reaction which converts serine to glycine.

(D) The function of the mesophyll cell is to increase the CO2 concentration in the bundle sheath cell so that the destructive side reaction with O2 is prevented.

(E) Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is not found in the mesophyll cell. 27. Which one of the following statements is most blatantly false?

(A) During the first minute after light is switched off from an illuminated suspension of green algae, the level of ribulose-1,5-bisphosphate will rise and the level of 3 phosphoglycerate will fall.

(B) Water appears on the left side of the Van Niel equation for photosynthesis (6 CO2 + 12 H2O → C6H12O6 + 6 H2O + 6 O2) because these H2O molecules provide all of the

oxygen for the 6 O2 on the right side of the equation. (C) During the first minute after CO2 is removed from an illuminated suspension of green algae, the

level of 3 phosphoglycerate will fall and the level of ribulose-1, 5-bisphosphate will rise. (D) In photosynthesis it takes a minimum of 8 photons to form two molecules of NADPH using

electrons from two water molecules. (E) Exactly 12 NADPH molecules are necessary to form 1 glucose molecule from 6 CO2 molecules.

28. Which one of the following statements is most blatantly false?

(A) In the pyruvate carboxylase mechanism, biotin is first carboxylated by CO2 in a reaction which is driven by the coupled hydrolysis of ATP, and then the carboxyl group of carboxybiotin is transferred to pyruvate in a subsequent reaction.

(B) Although lipoic acid is covalently bound to E2 of pyruvate dehydrogenase, the side chain of lipoic acid interacts with the active sites of E1 and E3 during the pyruvate dehydrogenase reaction sequence.

(C) Pyruvate dehydrogenase kinase is allosterically inactivated by acetyl CoA. (D) Pyruvate carboxylase is allosterically activated by acetyl CoA. (E) Phosphorylation of pyruvate dehydrogenase inactivates the enzyme.

29. Which one of the following statements about nitrogen fixation is blatantly false? (A) The transfer of electrons from ferredoxin to dinitrogenase (DN) is catalyzed by dinitrogenase

reductase (DNR). (B) Dinitrogenase is inactivated by oxygen, and one role of legumes such as clover in the symbiotic

relationship with nitrogen fixing bacteria is accordingly to maintain a low oxygen tension in the root nodules where the nitrogen fixing bacteria live.

(C) The products of the fixation of N2 include two molecules of NH3 and one molecule of H2. (D) Dinitrogenase contains molybdenum. (E) The conversion of NO3

Θ (nitrate) to N2 is carried out by aerobic soil bacteria but not by plants.

30. Which one of the following statements about one carbon transfers is blatantly false? (A) The antibiotic sulfanilamide does not affect humans because humans cannot synthesize folic

acid. (B) Tetrahydrofolate (FH4) is required for the enzymatic conversion of serine to glycine. (C) The 14C label initially in carbon atoms 3 and 4 of glucose can label the methyl carbon atom of

S-adenosylmethionine. (D) S-adenosylmethionine is formed in an enzymatic reaction whose substrates are methionine and

ATP . (E) The synthesis of the purine rings adenine and guanine require one carbon units bound to

tetrahydrofolate (FH4). 31. Which one of the following statements is most blatantly false?

(A) Flavin mononucleotide is a prothestic group in Complex I. (B) Electron transport from UQH2 to cytochrome C pumps protons out of the mitochondria. (C) The formation of ATP and the reduction of O2 to H2O occur on opposite sides of the inner

mitochondrial membrane. (D) Cytochromes b and c1 are prosthetic groups in Complex III. (E) Cytochromes a and a3 are prosthetic groups in Complex IV.

32. Which one of the following statements is most blatantly false?

(A) In a transamination reaction, pyridoxamine phosphate and α ketoglutarate are converted to glutamate and pyridoxal phosphate.

(B) Vitamin B12 is required for the catabolism of propionyl CoA. (C) For each C = C in an unsaturated fatty acid, there will be one less FADH2 generated in FAO

than would be the case for a saturated fatty acid of the same length. (D) Six ATP equivalents of energy are required to synthesize one molecule of the TAG tripalmitoyl

glycerol (tripalmitin) from glycerol and three molecules of palmitate. (E) NH3 is produced from glutamate in the glutamate dehydrogenase reaction.

33. Which one of the following statements is most blatantly false? (A) Biotin is required for acetyl CoA carboxylase and for pyruvate carboxylase. (B) Thiamin pyrophosphate is required for pyruvate dehydrogenase and for α-ketoglutarate

dehydrogenase. (C) Coenzyme A is required for the synthesis of palmitate from pyruvate and for the synthesis of

glucose from pyruvate. (D) FAD is required for the conversion of palmitate to acetyl CoA and of acetyl CoA to CO2. (E) NADPH is required for the conversion of palmitoyl CoA to stearyl CoA (stearate is a C18

saturated fatty acid) and of stearyl CoA to oleyl CoA (oleate is a C18 unsaturated fatty acid).

34. Which of the following reactions would be expected to proceed in the direction shown under standard conditions (that is, starting with 1 M concentrations of each substrate and product), assuming that the appropriate enzymes are present to catalyze each reaction? (1) isocitrate + NAD+ → α-ketoglutarate + CO2 + NADH + H+ (2) malate + NAD+ → oxaloacetate + NADH + H+

(3) β-hydroxybutyrate + NAD+→ acetoacetate + NADH + H+

(4) lactate + NAD+→ pyruvate + NADH + H+

(A) 1 and 3 (B) 1, 2, 3 (C) 2, 4 (D) 4 only (E) All 35. Which one of the following statements is most blatantly false?

(A) In a liver cell the enolase reaction is essentially at equilibrium under conditions of active glycolysis and of active gluconeogenesis.

(B) The committed step in a biosynthetic pathway is the enzymatic step which converts a substrate with more than one metabolic fate to a product which can only be used in the biosynthetic pathway.

(C) Gsα is only able to activate adenylate cyclase if GTP is bound to it. (D) The activation of protein kinase by cAMP is an example of covalent regulation of enzymatic

activity . (E) The inhibition of acetyl CoA carboxylase by palmitoyl CoA is an example of "feedback

inhibition at the committed step."

36. Which one of the following statements is blatantly false? (A) In the synthesis of glycogen, UDP glucose pyrophorylase forms UDP glucose and

pyrophosphate from UTP and glucose-1-phosphate. (B) Atractyloside strongly inhibits photophosphorylation in the chloroplast by blocking the

translocation of ADP into the thylakoid lumen. (C) All of the 20 common amino acids are synthesized starting with intermediates from glycolysis,

the TCA cycle, or the phosphogluconate pathway. (D) The one carbon units bound to tetrahydrofolate can be in the methyl, hydroxymethyl, and

formyl oxidation states. (E) dTMP is synthesized from dUMP in an unusual methylation reaction in which the carbon donor

is N5,N10 -methylene tetrahydrofolate (the -CH2OH oxidation state) while the group transferred is the -CH3 (methyl) oxidation state.


(A) Insulin activates glucose uptake by muscle and adipose cells by increasing the number of GLUT 4 glucose transporter molecules in the plasma membranes of these cells.

(B) Insulin activates protein phosphatase and thereby converts the protein targets of protein kinase to the dephosphorylated state.

(C) Untreated insulin dependent diabetes and the fasting state are both characterized by high levels of blood ketone bodies (ketosis) and blood free fatty acids.

(D) In untreated diabetes glucagon levels are normal and insulin is inactive, which causes a shift to the phosphorylated state in protein kinase targets in liver cells.

(E) Fasting causes decreased levels of the enzymes phosphoenolpyruvate carboxykinase and acetyl CoA carboxylase in liver cells.


(A) Glucagon has receptors in liver and adipose cells, but not in muscle cells. (B) HMG CoA synthase catalyzes the committed step in cholesterol biosynthesis and is regulated by

phosphorylation by protein kinase. (C) Both AMP and fructose 2,6-bisphosphate allosterically activate phosphofructokinase I in liver

cells. (D) Caffeine inhibits cyclic nucleotide phosphodiesterase and thereby enhances the adrenalin

response in muscle cells. (E) Muscle glycogen is used preferentially during the first phase of aerobic exercise because the

ratio of ATP produced per O2 consumed is greater for glycogen than for fat.

39. Which one of the following statements is blatantly false? (A) The coat of a lipoprotein contains a single layer of glycerophospholipid molecules oriented so

that their polar head group is in contact with water and their hydrophobic fatty acid chains face the interior core.

(B) Although very low density lipoproteins (VLDLs) are larger than low density lipoproteins (LDLs), they have exactly the same content of cholesterol.

(C) The interior of very low density lipoproteins (VLDLs) is composed primarily of cholesteryl esters and triacylglycerols.

(D) Chylomicron remnants have only cholesteryl esters in their interior, and are primarily taken up by liver cells.

(E) Squalene has 30 carbon atoms and is formed from two molecules of the C15 molecule geranyl pyrophosphate.

40. You will find below several correctly drawn structures of important compounds in biochemistry.

Which of the following are represented among these structures? (1) FMNH2 (2) Biotin (3) tetrahydrofolate (4) cyclic AMP (5) S-adenosylmethionine (A) 1, 2, 3 (B) 1, 2, 3, 4 (C) All (D) 1,2,3,5 (E) 2, 3, 5

Multiple Choice. 1. 1. Consider the conversion of palmityl CoA to stearyl CoA, a C18 saturated fatty acid. Which of

the following statements about this conversion are true? 1. It will take one ATP equivalent of energy and two molecules of NADPH to synthesize stearyl

CoA from palmitoyl CoA and malonyl CoA. 2. If acetyl CoA is fully labeled with deuterium (i.e., CD3(CO)SCoA) and palmitoyl CoA is

unlabeled, two deuterium atoms will be incorporated per stearyl CoA formed. 3. Avidin, a protein which inhibits all biotin-dependent reactions, will inhibit the synthesis of

stearyl CoA from palmitoyl CoA and malonyl CoA. 4. If acetyl CoA is labeled with 14C in the methyl carbon and palmitoyl CoA is unlabeled, only

carbon 2 of stearyl CoA will be labeled.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) none are true

2. Which of the following statements are true? 1. The biological reducing agent used in the biosynthesis of glucose from pyruvate in a liver cell is

NADPH. 2. It takes two ATP equivalents of energy to incorporate glucose into glycogen. 3. Since the pyruvate dehydrogenase step in metabolism is irreversible, no 14C label will enter

glucose if an animal is given palmitate uniformly labeled with 14C. 4. It takes 6 ATP equivalents of energy to convert 2 lactate molecules to glucose.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All are true

3. Which of the following statements are true? 1. During the first minute after CO2 is removed from an illuminated suspension of green algae

undergoing active CO2 fixation, the level of 3 phosphoglycerate will rise and the level of ribulose-1,5-bisphosphate will fall.

2. During the first minute after light is switched off from an illuminated suspension of green algae undergoing active CO2 fixation into glucose, the level of ribulose-1,5-bisphosphate will rise and the level of 3 phosphoglycerate will fall.

3. When a suspension of green algae are given a short pulse of CO2 together with visible light, carbons 1 and 6 of glucose will be labeled most rapidly.

4. Water appears on the left side of the Van Niel equation for photosynthesis

(6 CO2 + 12 H2O → C6H12O6 + 6 H2O + 6 O2) because the 12 H2O molecules provide all of the oxygen for the 6 O2 on the right side of the equation.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) None are true 4. Which of the following statements are true?

1. All ATP molecules consumed in the fixation of 6 CO2 to glucose in a chloroplast are used in the

3-phosphoglycerate kinase step. 2. All NADPH molecules consumed in the fixation of 6 CO2 molecules to form one glucose

molecule are used in the glyceraldehyde-3-P dehydrogenase step. 3. Phosphoglucomutase, the enzyme that interconverts G1P and G6P, is required for muscle cells

to incorporate glucose into glycogen but not to generate pyruvate from a glucose subunit of glycogen.

4. Starting with 2 molecules of glyceraldehyde-3-phosphate, only one ATP equivalent per glucose is required to synthesize a glucose subunit of glycogen in a liver cell.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All are true 5. Which of the following statements about fatty acid biosynthesis are true?

1. 16 NADPH molecules are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

2. 7 ATP equivalents are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

3. Acetyl CoA carboxylase is activated by phosphorylation. 4. Palmitoyl CoA is an allosteric inhibitor of acetyl CoA carboxylase, the enzyme which catalyzes

the committed step in fatty acid biosynthesis.


6. Which of the following statements are true? 1. The conversion of malate to pyruvate in the cytosol requires one molecule of NADP+. 2. Aspirin irreversibly inhibits prostaglandin synthase by acetylating a serine residue in the

enzyme, and thereby prevents the synthesis of prostaglandins and thromboxanes. 3. The conversion of citrate to acetyl CoA by the action of citrate lyase in the cytosol is driven by

the hydrolysis of one ATP to ADP plus Pi and generates oxaloacetate as the other product.

4. Humans cannot synthesize a fatty acid with a carbon-carbon double bond in a carbon atom number position greater than C9 = C10.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All are true 7. A fall in blood glucose causes several dramatic changes in the major catabolic/anabolic pathways.

Which of the following statements about this response are true? 1. Glycogenolysis will be activated in the liver. 2. Triacylglycerol lipase will be activated in adipose cells. 3. Gluconeogenesis will be activated in the liver. 4. Fatty acid oxidation will be activated in the liver.


8. Which of the following statements are true?

1. Glucose-6-phosphatase is found in liver cells but not in muscle cells. 2. The formation of acetoacetyl CoA from acetoacetate and succinyl CoA never occurs in brain

cells.

3. Urea is formed only in liver cells. 4. The free fatty acids in blood are used by the brain for fuel after day 3 of a fast.



1. All of the carbons of cholesterol are derived from acetyl CoA. 2. β-hydroxy-β-methylglutaryl CoA reductase (= HMG-CoA reductase) catalyzes the committed

step in cholesterol biosynthesis and is inactivated by phosphorylation. 3. In cholesterol biosynthesis, isopentenyl pyrophosphate and dimethylallyl pyrophosphate

undergo a head-to-tail condensation to make geranyl pyrophosphate 4. The conversion of one molecule of HMG-CoA to mevalonic acid requires one molecule of

NADPH.


10. Which of the following statements about regulation are true? 1. An increase in blood glucagon levels will increase adenylate cyclase activity in liver cells but

not in muscle cells. 2. Protein kinase phosphorylates and thereby inactivates fructose bisphosphate II and activates

phosphofructokinase II in liver cells. 3. An increase in glucagon levels in the blood will decrease the activity of glycogen synthase in

liver cells. 4. An increase in fructose-2,6-bisphosphate levels will increase the rate of gluconeogenesis in

liver cells.



1. 1. The coat of a lipoprotein contains a single layer of glycerophospholipid molecules oriented so that their polar head group is in contact with water and their hydrophobic fatty acid chains face the interior core.

2. 2. Although very low density lipoproteins (VLDLs) are smaller than low density lipoproteins (LDLs), they have exactly the same content of cholesterol as the LDL from which they were derived.

3. 3. The interior of very low density lipoproteins (VLDLs) is composed primarily of cholesteryl esters and triacylglycerols.

4. 4. Chylomicron remnants have only cholesteryl esters in their interior, and are primarily taken up by extrahepatic tissues (such as muscle and adipose tissue) through a process known as endocytosis.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All are true 12. Which of the following statements are true?

1. 1. The conversion of NH3 to NO2– and the conversion of NO2- to NO3- are both carried out by

some soil bacteria. 2. 2. dinitrogenase reductase (=DNR) contains the element molybdenum (e.g., Mo). 3. 3. The products of reduction of N2 by nitrogenase include two molecules of NH3 and a

molecule of H2. 4. 4. Denitrification refers to the conversion of NO3- to N2, a reaction carried out by some

aerobic soil bacteria. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only

(E) All are true


1. 1. The committed step for fatty acid biosynthesis is catalyzed by the enzyme citrate lyase, and the allosteric activator for this enzyme is citrate.

2. 2. A molecule that is required for fatty acid biosynthesis by the fatty acid synthase complex is an allosteric inhibitor of carnitine acyl transferase I.

3. 3. The protein kinase dependent phosphorylation of citrate lyase inactivates the protein. 4. 4. Carbon dioxide is absolutely required for the synthesis of fatty acids from acetyl CoA and

for the synthesis of glucose from pyruvate. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only

(E) All are true 14. Which carbon atoms in palmitate will be labeled most rapidly when a cell extract which contains all

of the enzymes and substrates required for fatty acid synthesis except for acetyl CoA carboxylase is given CH3-(CO)SCoA plus excess O2C-14CH2-(CO)SCoA? (that is, the middle carbon of malonyl CoA is labeled with 14C) (A) C16 only (D) carbon numbers

2,4,6,8,10,12,14 only (B) C15 only (E) carbon numbers

1,3,5,7,9,11,13 only (C) all odd numbered carbon atoms

15. A common procedure for determining the effectiveness of compounds as precursors of glucose in

mammals is to fast the animal until the liver glycogen stores are depleted and then administer the substrate in question. A substrate that leads to a net increase in liver glycogen is termed glucogenic because it must first be converted to glucose-6-phosphate in the liver. Which of the following compounds are glucogenic?

1. alanine 2. a fatty acid with an odd number of carbons. 3. glycerol 4. acetoacetate



1. 1. Bundle sheath cells have Rubisco but mesophyll cells do not. 2. 2. Under low temperature conditions in which the Rubisco catalyzed reaction with O2 is

insignificant, it costs more ATP equivalents of energy to fix CO2 into glucose in a C4 plant than in a C3 plant.

3. 3. One function of the mesophyll cell is to increase the concentration of CO2 in the bundle sheath cell.

4. 4. Bundle sheath cells have chloroplasts but mesophyll cells do not. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only

(E) All are true 17. Which of the following statements are true?

1. 1. Protein kinase A inhibits glycolysis and activates gluconeogenesis in liver cells by phosphorylating the tandem enzyme PFKII/FDPase II.

2. 2. From what you know about the role of protein kinase A in liver cells, the predicted effect of the protein kinase A-dependent phosphorylation of pyruvate kinase is to inhibit the enzyme.

3. 3. Protein kinase A itself directly phosphorylates glycogen phosphorylase kinase but does not directly phosphorylate glycogen phosphorylase.

4. 4. Adrenalin increases the concentration of fructose-2,6-bisphosphate in liver cells. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only


1. 1. The α subunit of the G protein, Gα, is only able to activate adenylate cyclase if GTP is bound to it.

2. 2. The activation of protein kinase A (C2R2) is achieved by cAMP binding to the R2 regulatory subunits, which causes them to dissociate from the C2 catalytic subunits.

3. 3. The α subunit of the G protein, Gα, is only able to bind to the β and γ subunits if GDP is bound to it.

4. 4. Cyclic nucleotide phosphodiesterase is inhibited by caffeine only if the enzyme has Gα(GTP) bound to it.



1. 1. Gluconeogenesis in the liver occurs under conditions in which fatty acid oxidation is activated, and the concentration of acetyl CoA in the mitochondrial matrix is elevated.

2. 2. Glycogen synthase b, the phosphorylated form of the enzyme, is allosterically activatedby glucose-6-P

3. 3. AMP is an allosteric inhibitor of fructose bis phosphatase I (FBPase I). 4. 4. High levels of acetyl CoA in the matrix inhibit pyruvate dehydrogenase and pyruvate

carboxylase. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only


1. 1. In humans, serine and glycine are non-essential amino acids because serine is synthesized from 3 phosphoglycerate and glycine is synthesized from serine..

2. 2. The conversion of serine to glycine and the conversion of glycine to NH4 and CO2 both generate one carbon units bound to tetra hydrofolate (=FH4), namely N5-N10 methylene FH4.

3. 3. The one carbon units bound to FH4 can be in the methyl, hydroxymethyl, and formyl oxidation states.

4. 4. In the thymidylate synthase reaction, N5-N10 methylene FH4 plus deoxyUMP are converted to deoxyTMP (=TMP) plus dihydrofolate (=FH2).


21. Which of the following statements are completely true ?

1. 1. DNP will completely inhibit the oxidation of glucose to 6 CO2. 2. 2. DNP will prevent the generation of any net ATP equivalents in the complete oxidation of

lactate to 3 CO2.

3. 3. DNP will prevent the generation of any net ATP equivalents in the complete oxidation of palmitate to 16 CO2 .

4. 4. there will be four ATP equivalents produced per glucose molecule in the presence of DNP. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only

(E) None are true 22. The following graph represents the hypothetical results of an experiment in which the amount of O2

consumed is measured over a time interval during which intact mitochondria are treated sequentially with five substances. The identity of these 5 substances can be inferred from their effect on the amount of O2 consumed. Assume that Pi and an abundant source of matrix NADH are present.

(A) 1 = ADP 2 = atractyloside 3 = DNP 4 = Antimycin A 5 = succinate

(B) 1 = arsenate 2 = rotenone 3 = ascorbate 4 = CN 5 = DNP

(C) 1 = ADP 2 = oligomycin 3 = DNP 4 = CN 4 = arsenate

(D) 1 = arsenate 2 = Rotenone 3 = succinate 4 = CN 5 = DNP

(E) 1 = ADP 2 = oligomycin 3 = DNP 4 = Rotenone 5 = succinate 23. When a cell extract containing all of the enzymes of glycolysis and the TCA cycle is incubated

aerobically with Glucose-6-14C, what percentage of the original label will remain in oxaloacetate after two turns of the TCA cycle? (In this problem assume that any label which enters the cycle does so in the first citrate synthase step, and that the acetyl CoA entering in the second and later turns of the TCA cycle is unlabeled.)

(A) 0% (B) 25% (C) 50% (D) 75% (E) 100% 24. Which one of the following statements is blatantly false?

(A) The net ATP equivalents produced per glucose subunit of glycogen in an anaerobic muscle cell is 3.

(B) The net ATP equivalents produced by substrate level phosphorylation in the complete aerobic catabolism of glucose to 6CO2 is 4 per glucose.

(C) The net ATP equivalents produced in the complete aerobic catabolism of pyruvate in a muscle cell is 15 per pyruvate.

(D) The net ATP equivalents produced per glucose in an anaerobic liver cell treated with arsenate is zero.

(E) In the complete aerobic catabolism of lactate to 3 CO2, 5 oxygen atoms are reduced to 5 molecules of H2O.

25. If 2 [14C] acetyl-CoA is added to a rat liver homogenate that is synthesizing cholesterol, where will

the 14C label appear in isopentenyl pyrophosphate?

(A) Carbon 1 only (D) Carbons 1,3 and 5 only (B) Carbons 1 and 3 only (E) Carbons 2,4, and 5 only (C) Carbons 2 and 4 only 26. Which of the following statements are true?

1. Under steady state conditions in a typical cell, the ability of ATP hydrolysis to do useful work (e.g., drive biosynthetic reactions) is given by ∆G°′ = –30.5 kJ/mole.

2. In a typical liver cell, the reaction catalyzed by pyruvate kinase will have a higher ratio of the products of the reaction, pyruvate and ATP, to the reactants, ADP and phosphoenolpyruvate, than would be expected if the reaction were at equilibrium.

3. The rate of ATP generating pathways is increased by higher energy charge. 4. AMP is never an allosteric activator for regulatory enzymes in ATP-utilizing biosynthetic

pathways.

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) None are

true 27. Which of the following statements are true?

1. The enzymatic conversion of NH4+ plus α−ketoglutarate to glutamate requires NADPH.

2. In the first step of the reaction catalyzed by a aminotransferase (or transaminase), alanine + enzyme-pyridoxal P will be converted to pyruvate + enzyme-pyridoxamine P.

3. GTP is an allosteric inhibitor of glutamate dehydrogenase. 4. The allosteric activator of carbamoyl phosphate synthetase is N-acetyl glutamate. (A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All are true

28. When O2 is added to a suspension of yeast cells which have been growing anaerobically on glucose, the rate of glucose consumption falls dramatically and ethanol ceases to be produced. Which of the following statements about this effect, called the Pasteur effect, are true ?

1. 1. The energy charge will decrease when O2 is added. 2. 2. The concentration of NADH in the mitochondrial matrix will increase when O2 is added. 3. 3. The phosphofructokinase reaction will be inhibited by higher AMP levels when O2 is added. 4. 4. Assuming ATP needs are constant, the rate of CO2 evolution will increase when O2 is added. (A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) None are true


1. S-adenosyl methionine (=SAM) is a methyl group donor in biosynthetic reactions.

2. 2. In the first step of triacylglycerol formation, a fatty acyl CoA molecule reacts with glycerol to form monoacylglycerol.

3. Oxygen (O2) is required for the synthesis of unsaturated fatty acids in mammalian cells. 4. In the formation of phosphatidyl ethanolamine, diacylglycerol reacts with UDP-O-CH2CH2NH3

+ to form phosphatidyl ethanolamine and UMP.

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) All are

true 30. You are studying catabolism and electron transport in a minced tissue preparation of pigeon breast

muscle which contains all of the enzymes of glycolysis and intact mitochondria. You already know that this tissue is capable of perfectly normal aerobic and anerobic glycolysis. Furthermore the TCA cycle and electron transport can all function normally. Now in the presence of O2 and glucose, you add an inhibitor of electron transport to the aerobically respiring tissue. Which of the following possible results are you likely to see?

1. 1. O2 consumption increases. 2. 2. All CO2 production from glucose ceases. 3. 3. The NADH/NAD⊕ ratio in the mitochondria decreases. 4. 4. The rate of glucose consumption increases. (A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) None are

true

31. Which of the following enzymes are required for the synthesis of glucose from pyruvate in a liver cell? 1. Pyruvate kinase 2. Phosphoenolpyruvate carboxykinase 3. Phosphofructokinase 4. Fructose bisphosphatase (A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) All are true 32. Which of the following statements about mitochondria are true?

1. 1. Flavin adenine dinucleotide (FAD) is a prosthetic group in Complex I. 2. 2. Electron transport from UQH2 to NAD+ pumps protons out of the mitochondria. 3. 3. The formation of ATP and the reduction of O2 to water occur on opposite sides of the inner

mitochondrial membrane. 4. 4. In mitochondria incubated aerobically with a source of NADH, cytochrome b will be

completely reduced in mitochondria treated with rotenone. (A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) None are

true

33. One micromole of a fully tritiated, 16-carbon, straight-chain, saturated fatty acid C3H3(C3H2)18COO3H

is added to a preparation of disrupted mitochondria, which degrades it completely to acetyl CoA. If the 10 micromoles of product are re-isolated from the reaction mixture, hydrolyzed to free acetate, and assayed for radioactivity, what will be their overall tritium-to-carbon ratio (i.e., 3H : C)?

(A) 3 : 5 (B) 3 : 8 (C) 1 : 2 (D) 5 : 8 (E) 1 : 1 34. Which of the following statements about the light reactions of photosynthesis are true?

1. 1. Photosystem II carries out a 4 electron transfer in which the 4 electrons come from the formation of O2 from 2 H2O molecules, and the 4 electrons are transferred to the Mn complex.

2. 2. Plastoquinone (QB) is a 2 electron carrier which transfers electrons from photosystem II to the cytochrome bf complex.

3. 3. Photosystem I accepts electrons from plastocyanin, a 1 electron carrier protein which contains copper and is located in the thylakoid lumen of the chloroplast.

4. 4. In photosystem I, the energy of the photon of light is used to drive a separation of charge, with the formation of pheophytin – and P680+ .

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) None are

true

35. What is the actual free energy of ATP hydrolysis, ∆G′, in a human erythrocyte when the steady state

concentrations are: ATP = 3 mM; ADP = 3 x 10-5 M; and Pi = 2 mM? Choose the most nearly correct answer.

(A) -47 (B) -50 (C) -52 (D) -55 (E) -57

36. What is the equilibrium constant for the reduction of pyruvate to lactate at 25˚C? Choose the most

nearly correct answer.

(A) 2.5 x 105 (B) 2.5 x 104 (C) 2.5 x 102 (D) 2.5 x 103 (E) 4 x 10-6

37. Given the following information:

uncoupled: A → B Keq = 10-3

coupled: ATP + A → B + ADP + Pi Keq = 102

By what approximate factor will the equilibrium ratio of [B/A] be increased in the coupled reaction

when the steady state ratio of ATP to ADP and Pi is 500? (A) 109 (B) 5 x 108 (C) 108 (D) 5 x 107 (E) 107

38. Which of the following statements are true? 1. Glucagon is released by the α islet cells of the pancreas, while insulin is released by the β islet

cells. 2. Insulin activates protein phosphatase and thereby causes proteins that are phosphorylated by

protein kinase to shift to the dephosphorylated state. 3. In untreated diabetes, glucagon levels are normal and insulin is inactive, which causes a shift to the

phosphorylated state in protein kinase target proteins in liver cells. 4. Insulin activates the GLUT 4 glucose transporter in liver cells and thereby causes these cells to

take up glucose from blood.

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) All are true

(lactate)(NAD+) Keq =

(pyruvate)(NADH) = ?

39. Which of the following statements are true? 1. The substrate for the first step in the pentose phosphate pathway is glucose-1-phosphate. 2. Both the oxidative and non-oxidative branches of the phosphogluconate pathway are found in the

cytosol. 3. The electron pair carrier used by the oxidative branch of the phosphogluconate pathway is

NADP+, and the pathway functions to maintain the ratio of NADP+/NADPH far larger than the NAD+/NADH ratio in cells.

4. The prosthetic group for transketolase in the non-oxidative branch of the pentose phosphate pathway is thiamine pyrophosphate.

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) All

are true 40. You will find below several correctly drawn structures of important compounds in biochemistry.

Which of the following is not represented among these structures? (1) S-adenosyl methionine (2) folate (3) FMNH2 (4) pyridoxal phosphate (5)

UQH2

(A) 2,4,5 (B) 1,4 (C) 3,4,5 (D) 3 (E) 3,5

Multiple Choice.

1. Consider the conversion of palmityl CoA to stearyl CoA, a C18 saturated fatty acid. Which of the following statements about this conversion are true?

1) 1) It will take one ATP equivalent of energy and two molecules of NADPH to synthesize stearyl CoA from palmitoyl CoA and acetyl CoA.

2) 2) If acetyl CoA is fully labeled with deuterium (i.e., CD3(CO)SCoA) and palmitoyl CoA is unlabeled, one deuterium atom will be incorporated per stearyl CoA formed.

3) 3) Avidin, a protein which inhibits all biotin-dependent reactions, will inhibit the synthesis of stearyl CoA from palmitoyl CoA and acetyl CoA.

4) 4) If acetyl CoA is labeled with 14C in the carbonyl carbon and palmitoyl CoA is unlabeled, only carbon 17 of stearyl CoA will be labeled.

(A)1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All

2. 2. Which of the following statements are true?

1) 1) The biological reducing agent used in the synthesis of glucose from pyruvate is NADH, not NADPH.

2) 2) It takes one ATP equivalent of energy to incorporate glucose-1-phosphate into glycogen.

3) 3) It takes 6 ATP equivalents of energy to convert 2 lactate molecules to glucose. 4) 4) Since the pyruvate dehydrogenase step in metabolism is irreversible, no 14C label will

enter glucose if an animal is given palmitate uniformily labeled with 14C.

(A) 1 and 3 (B) 1, 2 and 3 (C) 2 and 4 (D) 4 only (E) All

3. 3. Which of the following statements are true? 1) 1) Exactly 12 NADPH molecules and 18 ATP molecules are necessary to form 1 glucose

molecule from 6 CO2 molecules. 2) 2) During the first minute after CO2 is removed from an illuminated suspension of green

algae undergoing active CO2 fixation, the level of 3 phosphoglycerate will rise and the level of glyceraldehyde 3 phosphate will fall.

3) 3) Water appears on the left side of the Van Niel equation for photosynthesis 4) 4) (6 CO2 + 12 H2O → C6H12O6 + 6 H2O + 6 O2) because the 12 H2O molecules provide

all of the oxygen for the 6 O2 on the right side of the equation. 5) 5) During the first minute after light is switched off from an illuminated suspension of

green algae undergoing active CO2 fixation into glucose, the level of ribulose-1,5-bisphosphate will rise and the level of 3 phosphoglycerate will fall.


4. 4. Which of the following statements are true? 1) 1) All of the 12 NADPH molecules consumed in the fixation of 6 CO2 molecules to form

one glucose molecule are used in the glyceraldehyde-3-P dehydrogenase step. 2) 2) 12 of the 18 ATP molecules consumed in the fixation of 6 CO2 to glucose are used in

the 3-phosphoglycerate kinase step.

3) 3) Phosphoglucomutase, the enzyme that interconverts G1P and G6P, is required for muscle cells to incorporate glucose into glycogen but not to generate energy from free glucose.

4) 4) Starting with 2 molecules of dihydroxyacetone phosphate, only one ATP equivalent per glucose is required to synthesize a glucose subunit of glycogen in a liver cell.


5. 5. Which of the following statements about fatty acid biosynthesis are true? 1) 1) 7 NADH and 7 FADH2 molecules are required to synthesize a molecule of palmitate

starting with 8 acetyl CoA molecules in the cytosol. 2) 2) Citrate is a positive effector of acetyl CoA carboxylase, 3) 3) 8 ATP equivalents are required to synthesize a molecule of palmitate starting with 8

acetyl CoA molecules in the cytosol.

4) 4) Palmitoyl CoA is a negative effector of acetyl CoA carboxylase, the enzyme which catalyzes the committed step in fatty acid biosynthesis.


6. 6. Which of the following statements are true? 1) 1) The conversion of malic acid to pyruvic acid in the cytosol requires one molecule of

NAD+. 2) 2) Aspirin irreversibly inhibits prostaglandin synthase by acetylating a serine residue in the

enzyme, and thereby prevents the synthesis of prostaglandins and thromboxanes. 3) 3) The conversion of citrate to acetyl CoA by the action of citrate lyase in the cytosol is

driven by the hydrolysis of one ATP to ADP plus Pi and generates malate as the other product.

4) 4) Humans cannot synthesize a fatty acid with a carbon-carbon double bond in a carbon atom number position greater than C9 = C10.


7. A fall in blood glucose causes several dramatic changes in the major catabolic/anabolic pathways. Which of the following statements about this response are true?

1) 1) Glycogenolysis will be activated in the liver. 2) 2) Fatty acid oxidation will be inhibited in the liver. 3) 3) Triacylglycerol lipase will be activated in adipose cells. 4) 4) Glycolysis will be activated in the liver.



1) 1) Glucose-6-phosphatase is found in liver cells but not in muscle cells. 2) 2) The formation of acetoacetyl CoA from acetoacetate and succinyl CoA never occurs in liver

cells. 3) 3) Urea is formed only in liver cells. 4) 4) The free fatty acids in blood are never used by the brain for fuel.



1) 1) β-hydroxy-β-methylglutaryl CoA synthase (= HMG-CoA synthase) catalyzes the committed step in cholesterol biosynthesis and is allosterically inhibited by cholesterol.

2) 2) All of the carbons of cholesterol are derived from acetyl CoA. 3) 3) In cholesterol biosynthesis, isopentenyl pyrophosphate and dimethylallyl pyrophosphate

undergo a head-to-tail condensation to make farnesyl pyrophosphate 4) 4) HMG-CoA is an obligatory intermediate in the synthesis of ketone bodies from acetyl CoA

.


10. Which of the following statements about regulation in liver cells are true?

1) 1) An increase in blood glucagon levels will increase adenylate cyclase activity in liver cells but not in muscle cells.

2) 2) Protein kinase phosphorylates and thereby activates fructose bisphosphate II and inactivates phosphofructokinase II in liver cells.

3) 3) An increase in glucagon levels in the blood will decrease the activity of glycogen synthase in liver cells.

4) 4) An increase in fructose-2,6-bisphosphate levels will increase the rate of glycolysis in liver cells.



(A) (A) The coat of a lipoprotein contains a single layer of glycerophospholipid molecules oriented so that their polar head group is in contact with water and their hydrophobic fatty acid chains face the interior core.

(B) (B) The interior of chylomicrons is composed primarily of cholesteryl esters and triacylglycerols. (C) (C) Chylomicron remnants have only cholesteryl esters in their interior, and are primarily taken

up by extrahepatic tissues (such as muscle and adipose tissue) through a process known as endocytosis.

(D) (D) Low density lipoproteins (LDLs) have exactly the same content of cholesterol as the very low density lipoproteins (VLDLs) from which they were derived.

(E) (E) Familial hypercholesterolemia is caused by a deficiency in LDL receptors, which inhibits the uptake of LDLs by tissues and so elevates blood cholesterol levels.


(A) (A) The conversion of NH3 to NO2– and the conversion of NO2- to NO3- are both carried out by anaerobic soil organisms.

(B) (B) The nitrogenase reaction requires the overall hydrolysis of 16 ATP equivalents to reduce N2 to ammonia.

(C) (C) The products of reduction of N2 by nitrogenase include two molecules of NH3 and a molecule of H2.

(D) (D) The dinitrogenase subunit of the nitrogenase complex contains the element molybdenum (e.g., Mo).

(E) (E) Denitrification refers to the conversion of NO3- to N2, a reaction carried out by some soil bacteria.


(A) (A) The committed step for fatty acid biosynthesis is catalyzed by the enzyme acetyl CoA carboxylase.

(B) (B) Both cholesterol biosynthesis and fatty acid biosynthesis are regulated in part by feedback inhibition by the final biosynthetic product.

(C) (C) A molecule that is required for fatty acid biosynthesis by the fatty acid synthase complex inhibits fatty acid oxidation.

(D) (D) The protein kinase dependent phosphorylation of acetyl CoA carboxylase activates the protein.

(E) (E) Carbon dioxide is absolutely required for the synthesis of fatty acids from acetyl CoA and for the synthesis of glucose from pyruvate.

14. Which carbon atoms in palmitate will be labeled most rapidly when a cell extract which contains all of the enzymes and substrates required for fatty acid synthesis except for acetyl CoA carboxylase is given 14CH3(CO)SCoA plus excess O214CCH2(CO)SCoA?

(A) C16 only (D) all even numbered carbon atoms

(B) C15 only (E) carbon numbers 1,3,5,7,9,11,13 only

(C) all odd numbered carbon atoms

15. A common procedure for determining the effectiveness of compounds as precursors of glucose in mammals is to fast the animal until the liver glycogen stores are depleted and then administer the substrate in question. A substrate that leads to a net increase in liver glycogen is termed glucogenic because it must first be converted to glucose-6-phosphate in the liver. Which one of the following compounds is not glucogenic?

(A) alanine (D) glycerol

(B) a fatty acid with an odd number of carbons. (E) β-hydroxybutyrate

(C) glutamate


(A) (A) Bundle sheath cells have Rubisco but mesophyll cells do not. (B) (B) Bundle sheath cells have chloroplasts but mesophyll cells do not. (C) (C) One function of the mesophyll cell is to increase the concentration of CO2 in the bundle

sheath cell. (D) (D) One product of the Rubisco-catalyzed reaction with oxygen is phosphoglycolate. (E) (E) Under low temperature conditions in which the Rubisco catalyzed reaction with O2 is

insignificant, it costs more ATP equivalents of energy to fix CO2 into glucose in a C4 plant than in a C3 plant.


(A) (A) Protein kinase A inhibits glycolysis and activates gluconeogenesis in liver cells by phosphorylating the tandem enzyme PFKII/FDPase II.

(B) (B) Protein kinase A phosphorylates and thereby activates glycogen phosphorylase kinase but not glycogen phosphorylase.

(C) (C) Protein kinase A phosphorylates and thereby inactivates glycogen synthase. (D) (D) Adrenalin increases the concentration of fructose-2,6-bisphosphate in liver cells. (E) (E) From what you know about the role of protein kinase A in liver cells, the predicted effect of

the protein kinase A-dependent phosphorylation of pyruvate kinase is to inhibit the enzyme.


(A) (A) The activation of protein kinase A (C2R2) is achieved by cAMP binding to the R2 regulatory subunits, which causes them to dissociate from the C2 catalytic subunits.

(B) (B) The α subunit of the stimulatory G protein, Gsα, is only able to activate adenylate cyclase if GTP is bound to it.

(C) (C) The α subunit of the stimulatory G protein, Gsα, is only able to bind to the β and γ subunits if GDP is bound to it.

(D) (D) A given adrenalin receptor complex can in principle activate more than one stimulatory G protein.

(E) (E) Adenylate cyclase is inhibited by caffeine only if the enzyme has Gsα (GTP) bound to it.


(A) (A) AMP is an allosteric inhibitor of fructose bis phosphatase I (FBPase I). (B) (B) Citrate is an allosteric activator of FBPase I and an allosteric inhibitor of

phosphofructokinase I (PFKI). (C) (C) Glycogen synthase b, the phosphorylated form of the enzyme, is allosterically activated by

glucose-6-P. (D) (D) Gluconeogenesis in the liver occurs under conditions in which fatty acid oxidation is

activated, and the concentration of acetyl CoA in the mitochondrial matrix is elevated. (E) (E) High levels of acetyl CoA in the matrix inhibit pyruvate dehydrogenase and pyruvate

carboxylase.


(A) (A) All of the 20 common amino acids are synthesized starting with intermediates from glycolysis, the TCA cycle, or the phosphogluconate pathway.

(B) (B) In humans, serine and glycine are non-essential amino acids because serine is synthesized from 3 phosphoglycerate and glycine is synthesized from serine..

(C) (C) The conversion of serine to glycine and the conversion of glycine to NH4 and CO2 both generate one carbon units bound to tetra hydrofolate (=FH4), namely N5-N10 methylene FH4.

(D) (D) The one carbon units bound to FH4 can be in the methyl, hydroxymethyl, and carboxyl oxidation states.

(E) (E) In the thymidylate synthase reaction, N5-N10 methylene FH4 plus deoxyUMP are converted to deoxyTMP (=TMP) plus dihydrofolate (=FH2).

21. Which one of the following statements is completely true ?

(A) (A) DNP will completely inhibit the oxidation of glucose to 6 CO2. (B) (B) DNP will prevent the generation of any net ATP equivalents in the complete oxidation of

lactate to 3 CO2. (C) (C) DNP will prevent the generation of any net ATP equivalents in the complete oxidation of

palmitate to 16 CO2 . (D) (D) Under anaerobic conditions, there will be two ATP equivalents produced per glucose

molecule in the presence of DNP. (E) (E) Under anaerobic conditions, there will be one ATP equivalent produced per pyruvate in the

presence of DNP.

22. The following graph represents the hypothetical results of an experiment in which the amount of O2 consumed is measured over a time interval during which intact mitochondria are treated sequentially with five substances. The identity of these 5 substances can be inferred from their effect on the amount of O2 consumed. Assume that Pi and an abundant source of matrix NADH are present.

(A) 1 = ADP 2 = atractyloside 3 = DNP 4 = rotenone 5 = succinate

(B) 1 = arsenate 2 = rotenone 3 = ascorbate 4 = CN 5 = DNP

(C) 1 = ADP 2 = oligomycin 3 = DNP 4 = CN 4 = arsenate

(D) 1 = arsenate 2 = antimycin A 3 = succinate 4 = CN 5 = DNP

(E) 1 = arsenate 2 = oligomycin 3 = DNP 4 = Antimycin A 5 = succinate

23. When a cell extract containing all of the enzymes of glycolysis and the TCA cycle is incubated aerobically with Glucose-4-14C, what percentage of the original label will remain in oxaloacetate after two turns of the TCA cycle? (In this problem assume that any label which enters the cycle does so in the first citrate synthase step, and that the acetyl CoA entering in the second and later turns of the TCA cycle is unlabeled.)

(A) 0% (B) 25% (C) 50% (D) 75% (E) 100%


(A) (A) The net ATP equivalents produced per glucose subunit of glycogen in an anaerobic muscle cell is 3.

(B) (B) The net ATP equivalents produced by substrate level phosphorylation in the complete aerobic catabolism of glucose to 6CO2 is 2 per glucose.

(C) (C) The net ATP equivalents produced in the complete aerobic catabolism of pyruvate in a muscle cell is 15 per pyruvate.

(D) (D) The net ATP equivalents produced per glucose in an anaerobic liver cell treated with arsenate is zero.

(E) (E) In the complete aerobic catabolism of lactate to 3 CO2, 3 O2 molecules are reduced to 6 molecules of H2O.

25. Which of the following reactions would be expected to proceed in the direction shown under standard conditions, assuming that the appropriate enzymes are present to catalyze them?

1) 1) Pyruvate + NADH + H+ → lactate + NAD+ 2) 2) Malate + NAD+ → oxaloacetate + NADH + H+ 3) 3) Pyruvate + β-hydroxybutyrate → lactate + acetoacetate 4) 4) Malate + pyruvate → oxaloacetate + lactate

(A) 1,2,3 (B) 1,3 (C) 2,4 (D) 4 (E) All


1) 1) Under steady state conditions in a typical cell, the ability of ATP hydrolysis to do useful work (e.g., drive biosynthetic reactions) is given by ∆G°′ = –30.5 kJ/mole.

2) 2) The rate of ATP generating pathways is increased by higher energy charge. 3) 3) In the reaction catalyzed by pyruvate kinase, the concentration of the products of the

reaction, pyruvate and ATP, are much greater than would be expected if the reaction were at equilibrium with its reactants ADP and phosphoenolpyruvate.

4) 4) ATP could be a positive effector for regulatory enzymes in ATP-utilizing biosynthetic pathways.



(A) (A) Thiamin pyrophosphate is required for pyruvate dehydrogenase. (B) (B) Biotin is required for pyruvate carboxylase and for acetyl CoA carboxylase. (C) (C) Lipoic acid is required for α-ketoglutarate dehydrogenase and for pyruvate dehydrogenase. (D) (D) Pyridoxal phosphate is required for glutamate/aspartate transaminase and for glutamate

dehydrogenase. (E) (E) Heme is a required prosthetic group for Complex III and IV but not for Complex I.

28. When O2 is added to a suspension of yeast cells which have been growing anaerobically on glucose, the rate of glucose consumption falls dramatically and ethanol ceases to be produced. Which of the following statements about this effect, called the Pasteur effect, is blatantly false?

(A) (A) The concentration of NADH in the mitochondrial matrix will decrease when O2 is added. (B) (B) The phosphofructokinase reaction will be inhibited by higher ATP levels when O2 is added. (C) (C) Assuming ATP needs are constant, the theoretical decrease in glucose consumption when O2

is added is 18-fold. (D) (D) Assuming ATP needs are constant, the rate of CO2 evolution will increase when O2 is added. (E) (E) The energy charge will increase when O2 is added.

29. When a muscle goes from rest to strenuous exercise, the rate of O2 consumption can go up by over 20 fold. Which of the following statements about the metabolic changes caused by strenuous exercise are true? (Assume that the muscle remains completely aerobic during the strenuous exercise.)

1) 1) The rate of ATP utilization by the muscle cell must increase by at least 20 fold during strenuous exercise.

2) 2) The concentration of ADP in the cytosol and matrix must increase during strenuous exercise. 3) 3) The concentration of NAD+ in the matrix must increase during strenuous exercise. 4) 4) The magnitude of the proton gradient across the inner mitochondrial membrane will be

exactly the same when the muscle is at rest or during strenuous exercise.


30. You are studying catabolism and electron transport in a minced tissue preparation of pigeon breast muscle which contains all of the enzymes of glycolysis and intact mitochondria. You already know that this tissue is capable of perfectly normal aerobic and anerobic glycolysis. Furthermore the TCA cycle and electron transport can all function normally. Now in the presence of O2 and glucose, you add an inhibitor of electron transport to the aerobically respiring tissue. Which of the following possible results are you least likely to see?

(A) (A) O2 consumption falls dramatically. (B) (B) The NADH/NAD⊕ ratio in the mitochondria increases. (C) (C) All CO2 production from glucose ceases. (D) (D) ATP synthesis from glucose decreases. (E) (E) The rate of glucose consumption decreases.

31. Foolhardy Pharmaceuticals has just sent you a sample of "Xenomycin", a newly discovered antibiotic tht inactivates one enzyme in carbohydrate metabolism. Included with the sample is the information given below. Unfortunately, they forget to list which enzyme is inactivated by Xenomycin. What is the name of the enzyme?

Yeast grown anaerobically with glucose as the sole carbon source No Xenomycin (+)

Xenomycin #ATP/Glucose 2 0 Yeast grown anaerobically with 14C labeled glucose Position of 14C in

Ethanol

(-) Xeno (+) Xeno glucose-1-14C 2 - glucose-2-14C 1 - glucose-3-14C - - glucose-4-14C - - glucose-5-14C 1 1 glucose-6-14C 2 2

(A) (A) phosphoglycerate kinase (B) (B) triose phosphate isomerase (C) (C) pyruvate kinase (D) (D) transketolase (E) (E) aldolase

32. Which one of the following statements about mitochondria is most blatantly false?

(A) (A) Flavin mononucleotide (FMN) is a prothetic group in Complex I. (B) (B) Electron transport from UQH2 to cytochrome c pumps protons out of the mitochondria. (C) (C) The formation of ATP and the reduction of O2 both occur on the matrix side of the inner

mitochondrial membrane. (D) (D) Cytochrome b, a prosthetic groups in Complex III, will be completely reduced in

mitochondria treated with rotenone. (E) (E) Complex IV, also called cytochrome oxidase, has the capacity to hold 4 electrons and to carry

out the 4 electron reduction of O2 to 2 H2O.

33. One micromole of a fully tritiated, 20-carbon, straight-chain, saturated fatty acid C3H3(C3H2)18COO3H is added to a preparation of disrupted mitochondria, which degrades it completely

to acetyl CoA. If the 10 micromoles of product are re-isolated from the reaction mixture, hydrolyzed to free acetate, and assayed for radioactivity, what will be their overall tritium-to-carbon ratio (i.e., 3H : C)?

(A) 3 : 5 (B) 3 : 8 (C) 1 : 2 (D) 5 : 8 (E) 1 : 1

34. Which one of the following statements about the light reactions of photosynthesis is most blatantly false?

(A) (A) Photosystem II carries out a 4 electron transfer in which the 4 electrons come from the formation of O2 from 2 H2O molecules, and the 4 electrons are transferred to the Mn complex.

(B) (B) Plastoquinone (QB) is a 2 electron carrier which transfers electrons from photosystem II to the cytochrome bf complex.

(C) (C) Photosystem I accepts electrons from plastocyanin, a 1 electron carrier protein which contains copper and is located in the stroma of the chloroplast.

(D) (D) Ferredoxin accepts electrons from photosystem I and donates them to FNR (ferredoxin-NADP reductase).

(E) (E) In photosystem II, the energy of the photon of light is used to drive a separation of charge, with the formation of pheophytin – and P680+ .

35. What is the actual free energy of ATP hydrolysis, ∆G′, in a human erythrocyte when the steady state concentrations are: ATP = 2.25 mM; ADP = 0.25 mM; and Pi = 1.65 mM? Choose the most nearly correct answer.

(A) -52 (B) –55 (C) -60 (D) -65 (E) -35

36. What is the equilibrium constant for the reduction of pyruvate to lactate at 25˚C? Choose the most nearly correct answer.

(A) 3 x 10-5 (B) 50 (C) 2 x 102 (D) 3 x 103 (E) 4 x 104

37. Given the following information:

uncoupled: A → B Keq = 10-3

coupled: ATP + A → B + ADP + Pi Keq = 192

By what approximate factor will the equilibrium ratio of [B/A] be increased in the coupled reaction when the steady state ratio of ATP to ADP and Pi is 5000?

(A) 109 (B) 2 x 108 (C) 108 (D) 2 x 105 (E) 105

38. You will find below several correctly drawn structures of important compounds in biochemistry. Which of the following is not represented among these structures?



(A) cyclic AMP (B) Biotin (C) pyridoxamine phosphate (D) NADPH (E) the reduced form of plastoquinone

Multiple Choice. Choose only one answer for each question and enter it on the accompanying computer sheet. Please show all work on your exam for problems which involve calculations.

1. Consider the conversion of palmityl CoA to stearyl CoA, a C18 saturated fatty acid. Which of the following statements about this conversion are true?

1. 1. If acetyl CoA is fully labeled with deuterium (i.e., CD3(CO)SCoA) and palmitoyl CoA is unlabeled, 3 deuterium atoms will be incorporated per stearyl CoA formed.

2. 2. Avidin, a protein which inhibits all biotin-dependent reactions, will not inhibit the synthesis of stearyl CoA from palmitoyl CoA and acetyl CoA.

3. 3. If acetyl CoA is labeled with 14C in the methyl carbon and palmitoyl CoA is unlabeled, only carbon 18 of stearyl CoA will be labeled.

4. 4. It will take one ATP equivalent of energy and two molecules of NADPH to synthesize stearyl CoA from palmitoyl CoA and acetyl CoA.



1. 1. The biological reducing agent used in the synthesis of glucose from pyruvate is NADPH. 2. 2. It takes 2 ATP equivalents of energy to incorporate glucose into glycogen. 3. 3. Avidin, a protein that inhibits enzymes which require biotin, will inhibit the enzyme

phosphoenol pyruvate carboxykinase. 4. 4. It takes 6 ATP equivalents of energy to convert 2 lactate molecules to glucose.



In a liver cell that lacks triose phosphate isomerase:

1. 1. There will be a build up of dihydroxyacetone phosphate in the cytosol during glycolysis. 2. 2. Pyruvate can be converted to glucose in gluconeogenesis. 3. 3. There will be no net ATP equivalents produced from the conversion of glucose to lactate in

anaerobic glycolysis. 4. 4. Glucose labeled with 14C in carbon 1 will produce 3-phosphoglycerate labeled in the 1

carbon.


4. A suspension of green algae is given a short pulse of 14CO2 together with visible light. Which of the following statements are true? (Assume that only those intermediates specifically involved in CO2 fixation into glucose will be labeled.)

1. 1. Carbons 3 and 4 of glucose will be labeled rapidly. 2. 2. Carbon 1 of dihydroxyacetone phosphate will be labeled rapidly.

1. 1. O 2. 2. HOCH2—C—CH2O P 3. 3. 1 2 3

3. 3. The aldehyde carbon of glyceraldehyde-3-phosphate will be labeled rapidly. 4. 4. The carboxyl carbon of phosphoenol pyruvate will be labeled rapidly.


5. A fall in blood glucose causes several dramatic changes in the major catabolic/anabolic pathways in liver cells. Which of the following statements about this response are true?

1. 1. Fatty acid oxidation will be inhibited. 2. 2. Gluconeogenesis will be activated. 3. 3. Fatty acid biosynthesis will be activated. 4. 4. Glycogenolysis will be activated.


6. A fully tritiated, 20-carbon, straight-chain, saturated fatty acid C3H3(C3H2)18COO3H is added to a preparation of disrupted mitochondria, which degrades it completely to acetyl CoA. If the acetyl CoA products are re-isolated from the reaction mixture, hydrolyzed to free acetate, and assayed for radioactivity, what will be their overall tritium-to-carbon ratio? (i.e., 3H/C =)?

(A) 8 : 5 (B) 3 : 8 (C) 1 : 2 (D) 5 : 8 (E) 3 : 5

7. The following graph represents the hypothetical results of an experiment in which the amount of O2 consumed is measured over a time interval during which intact mitochondria are treated sequentially with five substances. The identity of these 5 substances can be inferred from their effect on the amount of O2 consumed. Assume that Pi and an abundant source of matrix NADH are present.

(IMAGE NOT AVAILABLE)

(A) 1 = Rotenone 2 = DNP 3 = ADP 4 = Atractyloside 5 = Arsenate

(B) 1 = Atractyloside 2 = ADP 3 = Arsenate 4 = Antimycin A 5 = Succinate

(C) 1 = Rotenone 2 = Arsenate 3 = DNP 4 = Antimycin A 5 = Succinate

(D) 1 = Oligomycin 2 = ADP 3 = Arsenate 4 = Rotenone 5 = Succinate

(E) 1 = Atractyloside 2 = ADP 3 = DNP 4 = Rotenone 5 = Succinate


1. 1. All of the 12 NADPH molecules consumed in the fixation of 6 CO2 molecules to form one glucose molecule are used in the glyceraldehyde-3-P dehydrogenase step.

2. 2. Starting with 2 molecules of consumed glyceraldehyde-3-phosphate, only one ATP equivalent per glucose is required to synthesize a glucose subunit of glycogen in a liver cell.

3. 3. Phosphoglucomutase, the enzyme that interconverts G1P and G6P, is required for muscle cells to incorporate glucose into glycogen but not to generate energy from free glucose.

4. 4. The 18 ATP molecules consumed in the fixation of 6 CO2 to glucose are used in the 3-phosphoglycerate kinase step.



1. 1. 14 NADPH molecules are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

2. 2. 7 ATP equivalents are required to synthesize a molecule of palmitate starting with 8 acetyl CoA molecules in the cytosol.

3. 3. The fatty acid synthase complex cannot synthesize fatty acids longer than CH3(CH2)14CO2H.

4. 4. Citrate is a negative effector of acetyl CoA carboxylase.



1. 1. Carnitine acyl transferase I (CAT I) is allosterically activated by malonyl CoA. 2. 2. The acetyl CoA used for fatty acid biosynthesis travels from the matrix to the cytosol by the

facilitated diffusion of acetyl CoA across the inner mitochondrial membrane. 3. 3. Humans cannot synthesize a fatty acid with a carbon-carbon double bond in a carbon atom

number position greater than C7 = C8. 4. 4. Aspirin irreversibly inhibits prostaglandin synthase by acetylating a serine residue in the

enzyme.



1. 1. Urea is formed only in liver cells. 2. 2. The formation of acetoacetyl CoA from acetoacetate and succinyl CoA never occurs in liver

cells. 3. 3. After a prolonged fast, brain can derive over half of its energy from ketone bodies. 4. 4. HMG-CoA is an obligatory intermediate in the synthesis of ketone bodies from acetyl CoA.


12. When O2 is added to a suspension of yeast cells which have been growing anaerobically on glucose, the rate of glucose consumption falls dramatically and ethanol ceases to be produced. Which of the following statements about this effect, called the Pasteur effect, are true?

1. 1. The energy charge will increase when O2 is added. 2. 2. Assuming ATP needs are constant, the rate of CO2 evolution will decrease when O2 is

added. 3. 3. The phosphofructokinase reaction will be inhibited by higher ATP levels when O2 is added. 4. 4. The NADH/NAD+ratio in the mitochondrial matrix will decrease when O2 is added.



1. 1. Antimycin A blocks electron transport at photosystem II in photosynthetic electron transport. 2. 2. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is not found in the mesophyll

cell.

3. 3. Bundle sheath cells have photosystem II but mesophyll cells do not. 4. 4. DNP allows free diffusion of H+ across the thylakoid membrane and thereby prevents ATP

synthesis.



1. 1. At the steady state mass action ratio of [ATP]/[ADP][Pi] in a typical cell cytosol, the coupled hydrolysis of both high energy bonds of ATP will increase the ratio of product to substrate in a biosynthetic reaction by 1016.

2. 2. At steady state in a cell, all reactions in glycolysis which are not under allosteric regulation have a standard free energy change (∆G′) of approximately zero.

3. 3. In the cytosol of cells, the steady state ratio of NADPH to NADP is far greater than the ratio of NADH to NAD .

4. 4. In a typical muscle cell, the reaction catalyzed by phosphofructokinase has a higher ratio of reactants to products than would be expected from the equilibrium constant for this reaction.


15. If 1 [14C] acetyl-CoA is added to a rat liver homogenate that is synthesizing cholesterol, where will the 14C label appear in isopentenyl pyrophosphate?

(A) Carbon 1 only (D) Carbons 1,3 and 5 only

(B) Carbons 1 and 3 only (E) Carbons 2,4, and 5 only

(C) Carbons 2 and 4 only

16. A cell extract containing all of the enzymes of glycolysis is incubated with 32P labeled ATP (i.e., Adenosine - P - P - 32 P). Assuming that all of the glucose used in the cell during the experiment is derived from blood glucose and that inorganic phosphate is unlabeled, which of the following labeled compounds would be formed? Assume pyruvate kinase is inactivated.

1. Glucose-6-32P 3. 132P, 632P-Fructose bisphosphate

2. 332P phosphoglycerate 4. 132P, 332P-Bisphosphoglycerate


17. You will find below several correctly drawn structures of important compounds in biochemistry. Which of the following are represented among these structures?

(1) FMNH2 (2) Biotin (3) tetrahydrofolate

(4) Pyridoxal phosphate (5) Galactose

(A) 1, 2, 3 (B) 1, 2, 3, 4 (C) All (D) 1,2,3,5 (E) 2, 3


1. 1. β-hydroxy-β-methylglutaryl CoA synthase (= HMG-CoA synthase) catalyzes the committed step in cholesterol biosynthesis.

2. 2. All of the carbons of cholesterol are derived from acetyl CoA. 3. 3. Cholesterol is a negative allosteric effector of HMG-CoA synthase. 4. 4. Squalene is a 30 carbon intermediate in cholesterol biosynthesis which is formed from two

farnesyl pyrophosphate molecules.


19. Which of the following statements about regulation in liver cells are true?

1. 1. A decrease in blood glucose will increase adenylate cyclase activity in liver cells. 2. 2. Protein kinase phosphorylates and thereby activates phosphofructokinase II and inactivates

fructose bisphosphate II in liver cells. 3. 3. An increase in glucagon levels in the blood will decrease the activity of glycogen synthase in

liver cells. 4. 4. A decrease in fructose-2,6-diphosphate levels will increase the rate of glycolysis in liver

cells.



1. 1. Acetyl CoA cannot be used to drive the net synthesis of glucose in mammalian cells because the pyruvate dehydrogenase step in metabolism is irreversible.

2. 2. For every ketone body that is completely catabolized to CO2 in a cell, there will be one less GTP formed in the TCA cycle.

3. 3. The synthesis of 4 molecules of acetoacetate from palmitoyl CoA by liver mitochondria will generate a net total of 7 FADH2 and 7 NADH molecules.

4. 4. The net yield of ATP equivalents in the complete aerobic catabolism of β−hydroxybutyrate is 26.



1. 1. Exactly 12 NADPH molecules and 18 ATP molecules are necessary to form 1 glucose molecule from 6 CO2 molecules.

2. 2. When C18O2 is added to green plants, only half of the 18O label is incorporated into glucose.

3. 3. Water appears on the left side of the Van Niel equation for photosynthesis 4. 4. (6 CO2 + 12 H2O ∅ C6H12O6 + 6 H2O + 6 O2) because the 12 H2O molecules provide all

of the oxygen for the 6 O2 on the right side of the equation. 5. 5. During the first minute after light is switched off from an illuminated suspension of green

algae undergoing active CO2 fixation into glucose, the level of ribulose-1,5-bisphosphate will rise and the level of 3 phosphoglycerate will fall.



1. 1. Addition of DNP to a suspension of mitochondria makes the overall reaction of electron transport from NADH to O2 far more endergonic.

2. 2. Mitochondrial complexes I, II, and IV use the energy from electron transport to drive the pumping of H+ out of the mitochondrion.

3. 3. Acceptor control refers to the fact that the activity of ATP synthase is limited by the concentration of phosphate in the mitochondrial matrix.

4. 4. In the absence of ADP, oxygen consumption by intact mitochondria is essentially zero because the energy obtained from the transfer of electrons from NADH to O2 approximately equals the energy required to pump protons out of the mitochondria.


23. Protein kinase A (also called cAMP-dependent protein kinase) can catalyze the phosphorylation of specific serine and threonine residues on target proteins. Which of the following enzymes are known to be directly phosphorylated by protein kinase A?

1. 1. glycogen synthase in liver cells 2. 2. triacylglycerol lipase in adipose cells 3. 3. Phosphofructokinase II/fructosebisphosphatase II in liver cells 4. 4. glycogen phosphorylase in liver cells



1. 1. The enzymatic conversion of NH4+ plus α−ketoglutarate to glutamate requires NADP+. 2. 2. In the first step of the reaction catalyzed by a aminotransferase (or transaminase), alanine +

enzyme-pyridoxal P will be converted to pyruvate + enzyme-pyridoxamine P. 3. 3. GTP is a positive allosteric effector of glutamate dehydrogenase. 4. 4. The conversion of glutamate to glutamine in the brain is driven by the hydrolysis of ATP to

ADP + Pi.


25. In 1906 Harden and Young carried out a series of classic studies on the fermentation of glucose to ethanol and CO2 by extracts of brewer's yeast and made the following observations. (1) Inorganic phosphate was essential to fermentation; when the supply of phosphate was exhausted, fermentation ceased before all the glucose was used. (2) During fermentation under these conditions, ethanol, CO2, and a bisphosphorylated hexose accumulated. Given this information and what you know, which of the following statements are true?

1. 1. Glucose fermentation is dependent upon the availability of Pi for glyceraldehyde phosphate dehydrogenase.

2. 2. The ratio of Pi consumed to CO2 evolved is 1. 3. 3. Ethanol must be produced in order to regenerate NAD for glyceraldehyde phosphate

dehydrogenase. 4. 4. Addition of arsenate to the extract will inhibit the evolution of CO2.


26. When a cell extract containing all of the enzymes of glycolysis and the TCA cycle is incubated aerobically with glucose-1,3-14C, what fraction of the original label will remain in oxaloacetate after two turns of the TCA cycle? [In this problem, assume that all label enters the cycle in the first citrate synthase step, and that the acetyl CoA entering in the second turn of the TCA cycle is unlabeled.]

(A) 0.125 (B) 0.25 (C) 0.33 (D) 0.50 (E) No label will remain

27. How many ATP equivalents will be produced in the complete aerobic catabolism of cytosolic glycerol phosphate? (Assume that the glycerol phosphate shuttle is operating.)

(A) 21 (B) 19 (C) 18 (D) 17 (E) 16

28. Inside adipose cells, the ∆G′ for the hydrolysis of ATP to ADP and Pi is about -48 kJ/mole. Given that the ∆Gο′ for ATP hydrolysis to ADP and Pi is —30.5 kJ/mol, and RT = 2.48 kJ/mol, what is the approximate ratio of [ATP] to [ADP][Pi] in these cells? Choose the most nearly correct answer.

(A) 5000/1 (B) 4000/1 (C) 2000/1 (D) 1000/1 (E) 500/1

29. What is the equilibrium constant for the reduction of pyruvate to lactate at 25šC? Choose the most nearly correct answer.

(A) 3 x 10-5 (B) 50 (C) 2 x 102 (D) 3 x 103 (E) 4 x 104

30. Given that the ∆G ′ for ATP hydrolysis to ADP and Pi is —30.5 kJ/mol, and RT = 2.48 kJ/mol, what is the actual free energy of ATP hydrolysis, ∆G′, in a human erythrocyte when the steady state concentrations are: ATP = 2.25 mM; ADP = 0.25 mM; and Pi = 1.65 mM? Choose the most nearly correct answer.

(A) -52 (B) -56 (C) -60 (D) -65 (E) -35


1. 1. The net ATP equivalents produced per glucose subunit of glycogen in an anaerobic muscle cell is 3.

2. 2. The net ATP equivalents produced per glucose in an anaerobic liver cell treated with arsenate is zero.

3. 3. The net ATP equivalents produced by substrate level phosphorylation in the complete aerobic catabolism of glucose to 6CO2 is 4 per glucose.

4. 4. In the complete aerobic catabolism of pyruvate to 3 CO2, 3 O2 molecules are reduced to 6 molecules of H2O.





1. 1. Methionine and ATP react to form S-adenosyl methionine, an activated methyl group donor that contains no phosphorous.

2. 2. In methotrexate treated cells, most of the folate will be in the dihydrofolate state. 3. 3. Homocysteine reacts with N5 methyl tetrahydrofolate to form methionine. 4. 4. Folate is a carrier of 1 carbon units in the methyl, formyl, and carboxyl oxidation states.


33. Which of the following statements about nitrogen fixation are true?

1. 1. In the reaction catalyzed by the nitrogenase complex, 8 electrons are transferred to N2 to form 2 molecules of NH3.

2. 2. The conversion of NH3 to NO2 and the conversion of NO3 to N2 are both carried out by aerobic soil bacteria.

3. 3. The conversion of NO3 to NH3 is carried out by soil bacteria but not by plants. 4. 4. The dinitrogenase subunit contains molybdenum (i.e., Mo) but the dinitrogenase reductase

subunit does not.



1. 1. In the structure of VLDL's and of chylomicrons, triacyl glycerols are found on the interior of the lipoprotein.

2. 2. Chylomicrons are synthesized only in the liver. 3. 3. LDL's retain most of the cholesterol originally in the VLDL from which they were formed. 4. 4. The major function of a high cholesterol level in membranes is to decrease the rate at which

membrane proteins move laterally within the membrane.



1. 1. Six ATP equivalents of energy are required to synthesize one molecule of the TAG tripalmitoyl glycerol from glycerol phosphate and three molecules of palmitate.

2. 2. CTP is required for the synthesis of glycerophospholipids. 3. 3. Diacylglycerol phosphate is an intermediate in the biosynthesis of all triacylglycerols. 4. 4. The major sites of TAG synthesis in humans are liver and adipose tissue.



1. 1. Plastoquinone transfers electrons between the cytochrome bf complex and photosystem I. 2. 2. Mitochondrial complex IV has 4 one electron carriers, which are cytochrome a, cytochrome

a3, and the 2 copper atoms, and receives electrons from cytochrome C. 3. 3. Ferredoxin transfers electrons from photosystem II and FNR (= ferredoxin NADP

reductase). 4. 4. Ubiquinone can receive electrons from complex I and complex II.


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