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CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism
General, Organic, & Biological ChemistryJanice Gorzynski Smith
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
2
CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism
Learning Objectives: Role in Metabolism of fatty acid oxidation, glycolysis, & Amino acid
catabolism Reactions catalyzed by: kinase, isomerase, dehydrogenase, decarboxylase,
carboxylase Glycolysis: steps & net reaction Pyruvate conversion to acetyl Coenzyme A Gluconeogenesis: steps in synthesis of glucose Catabolism of Triacylglycerols: beta-oxidation Synthesis of ketone bodies: ketogenesis Catabolism of Amino acids:
transamination & oxidative deamination Ketogenic vs glucogenic amino acid catabolism
CH 24 Homework:End of Chapter problems: 30, 36, 38, 42, 47, 52, 58, 60, 64, 68, 71, 75, 76, 78, 80, 82, 96, 98
Metabolism
3
Step 2 of Metabolism
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
• Fatty acid oxidation
• Glycolysis
• Amino Acid Catabolism
All lead to the production of Acetyl CoA
•In the catabolism of carbohydrates, glycolysis converts glucose into pyruvate, which is then metabolized into acetyl CoA.
Metabolism Step 2 of Metabolism
Metabolism Step 2 of Metabolism
•In the catabolism of lipids, fatty acids are converted into thioesters and then cleaved into many acetyl CoA units.
Metabolism Step 2 of Metabolism
•Amino acids are usually reassembled into new proteins.
•Since excess amino acids are not stored in the body, they can also be catabolized for energy.
•The amino groups (NH2) are converted to urea [(NH2)2C=O], which is excreted in urine.
Metabolism Step 2 of Metabolism: Urea Cycle
http://www.t3portal.org/T3_Portal_v1/!SSL!/WebHelp/ales_vancura Catabolism_of_amino_acids.htm
Biochemical Rxns
Common Enzymes
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed. 8
Biochemical Rxns
Common Enzymes: Example
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed. 9
•The transfer of a phosphate unit from ATP to the fructose 6-phosphate molecule is catalyzed by a kinase enzyme.
Glycolysis Definition
10Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Glycolysis is a linear, 10-step anaerobic pathway that converts glucose into two molecules of pyruvate.
•Steps [1] – [5] comprise the energy investment phase, where 2 ATP molecules are hydrolyzed.
•Steps [6] – [10] comprise the energy-generating phase, producing 1 NADH and 2 ATPs for each pyruvate formed.
•The 6-carbon glucose molecule is converted into two 3-carbon segments.
Glycolysis Energy Investment
11Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
Glycolysis Energy Generation
12Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
Glycolysis Step 1
13Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Step [1] begins with the phosphorylation of glucose into glucose 6-phosphate, using an ATP and a kinase enzyme.
Glycolysis Step 2
14Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Step [2] isomerizes glucose 6-phosphate to fructose 6-phosphate with an isomerase enzyme.
Glycolysis Step 3
15Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Step [3] is the phosphorylation of fructose 6-phosphate into fructose 1,6-bisphosphate with a kinase enzyme.
Steps [1-3] add 2 phosphate groups and isomerize a 6-membered ring into a 5-membered ring. Energy is stored as 2 ATP molecules.
Glycolysis Step 4
16Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Step [4] cleaves the fructose ring into a dihydroxy- acetone phosphate and a glyceraldehyde 3-phosphate.
Glycolysis Step 5
17Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•Step [5] isomerizes the dihydroxyacetone phosphate into another glyceraldehyde 3-phosphate.
•Thus, the first phase of glycolysis converts glucose into 2 glyceraldehyde 3-phosphate units.
Glycolysis Step 6
18Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•In step [6] the aldehyde end of the molecule is oxidized and phosphorylated by a dehydrogenase enzyme and NAD+; this produces 1,3-bisphospho- glycerate and NADH.
Glycolysis Step 7
19Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•In step [7], the phosphate group is transferred onto an ADP with a kinase enzyme, forming 3-phosphoglycerate and ATP.
Glycolysis Step 8
20Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•In step [8], the phosphate group is isomerized to a new position in 2-phosphoglycerate.
Glycolysis Step 9
21Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•In step [9], water is lost to form phosphoenol- pyruvate.
Glycolysis Step 10
22Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•In step [10], the phosphate is transferred to an ADP,yielding pyruvate and ATP with a kinase enzyme.
•The 2 glyceraldehyde 3-phosphate units are converted into 2 pyruvate units in Phase two of glycolysis.
•Overall, the energy-generating phase forms 2 NADHs and 4 ATPs.
Glycolysis Overall Reaction
23Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
•2 ATPs are used in phase one of glycolysis, and 4 ATPs are made in phase two of glycolysis.
•The net result is the synthesis of 2 ATPs from glycolysis
•The 2 NADHs formed are made in the cytoplasm and must be transported to the mitochondria to join the electron transport chain and make ATP.
Pyruvate can be converted into three possibleproducts depending on the conditions and the organism.
under aerobicconditions
under anaerobicconditions
in fermentationby microorganisms
Glycolysis Pyruvate
24Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
Glycolysis ATP Yield
25Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
Glycolysis ATP Yield
26Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.
2 x 2.5 ATP = 5 ATP
2 x 2.5 ATP = 5 ATP
2 ATP 6 x 2.5 = 15 ATP
2 x 1.5 = 3 ATP
Gluconeogenesis Definition
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed. 27
•Gluconeogenesis is the synthesis of glucose from noncarbohydrate sources—lactate, amino acids, or glycerol.
•Gluconeogenesis is an anabolic pathway since it results in the synthesis of larger molecules from smaller ones.
Gluconeogenesis Cori Cycle
Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed. 28