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REDOX REACTIONS
Reduction
• Electrons gained
• H atoms added
• from O > C
• Oxygen removed
• Energy Stored
• Anabolic
• Simple > complex
• Endergonic
• Photosynthesis
Oxidation
• Electrons lost
• H atoms lost
• From C to O
• Oxygen gained
• Energy released
• Catabolic
• Complex > simple
• Exergonic
• Cellular Respiration
REDOX REACTIONS∆G = ∆H - T∆S
Reduction
• Nonspontaneous
• ∆ G (+)
• >H , <S, >G
Oxidation
• Spontaneous
• ∆ G (-)
• <H , >S, <G
Photosynthesis vs. Respiration
• Photosynthesis:
6 H2O + 6 CO2 + energy C6H12O6 + 6 O2
reduction
oxidation
Respiration:
C6H12O6 + 6 O2 6 H2O + 6 CO2 + energy
reduction
oxidation
Figure 9.4 NAD+ as an electron shuttle
LE 9-5a
1/2 O2H2 +
H2O
Explosiverelease of
heat and lightenergy
Uncontrolled reaction
Fre
e en
erg
y, G
LE 9-5b
2 H+ + 2 e–
2 H
(from food via NADH)
Controlledrelease ofenergy for
synthesis ofATP ATP
ATP
ATP
2 H+
2 e–
H2O
+ 1/2 O2
1/2 O2
Cellular respiration
Fre
e en
erg
y, G
Electro
n tran
spo
rt chain
LE 9-5
2 H+ + 2 e–
2 H
(from food via NADH)
Controlledrelease ofenergy for
synthesis ofATP ATP
ATP
ATP
2 H+
2 e–
H2O
+ 1/2 O21/2 O2H2 +
1/2 O2
H2O
Explosiverelease of
heat and lightenergy
Cellular respirationUncontrolled reaction
Fre
e en
erg
y, G
Fre
e en
erg
y, G
Electro
n tran
spo
rt chain
3 Types of phosphorylation: ADPATP• Photophosphorylation - in Noncyclic Photosynthesis in
ETC between PSII & PSI;
• using the energy of sunlight to create a high-energy electron donor and a lower-energy electron acceptor.
• Substrate phosphorylation -in glycolysis and Krebs cycle;
• Direct transfer of Pi to ADP by an enzyme- A KINASE
• In both aerobic and anaerobic respiration – no O2 needed
• Oxidative phosphorylation- at ATP synthase; result of proton gradient; electrons from NADH or FADH2 transferred to O2
Figure 9.6 An overview of cellular respiration (Layer 1)
Figure 9.7 Substrate-level phosphorylation
Figure 9.6 An overview of cellular respiration (Layer 2)
Figure 9.6 An overview of cellular respiration (Layer 3)
Chemiosmosis
Glycolysis
• Glycolysis Animation option I (simple)
• Glycolysis Animation option II (intermediate)
• Glycolysis Animation option III (advanced)
LE 9-9a_1
Glucose
ATP
ADP
Hexokinase
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Glucose-6-phosphate
LE 9-9a_2
Glucose
ATP
ADP
Hexokinase
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Glucose-6-phosphate
Phosphoglucoisomerase
Phosphofructokinase
Fructose-6-phosphate
ATP
ADP
Fructose-1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetonephosphate
Glyceraldehyde-3-phosphate
LE 9-9b_1
2 NAD+
Triose phosphatedehydrogenase
+ 2 H+
NADH2
1, 3-Bisphosphoglycerate
2 ADP
2 ATPPhosphoglycerokinase
Phosphoglyceromutase
2-Phosphoglycerate
3-Phosphoglycerate
LE 9-9b_2
2 NAD+
Triose phosphatedehydrogenase
+ 2 H+
NADH2
1, 3-Bisphosphoglycerate
2 ADP
2 ATPPhosphoglycerokinase
Phosphoglyceromutase
2-Phosphoglycerate
3-Phosphoglycerate
2 ADP
2 ATPPyruvate kinase
2 H2OEnolase
Phosphoenolpyruvate
Pyruvate
GLUCOSEC-C-C-C-C-C
PGAL C-C-C PGAL C-C-C
PYRUVATEC-C-C
PYRUVATEC-C-C
ATP
ATP
NAD+ NAD+
NADH2 NADH2
GLYCOLYSIS
•Prepartory Steps•Energy Investment Phase
•Energy Payout Phase•Oxidation of NAD+•Substrate level phosphorylation of
ATP
ANAEROBIC RESPIRATION (WITH OR WITH OUT O2)
IN CYTOSOL
NADOX = NAD+
NADre = NADH
NET GAIN
2 ATP
2 NADH
Coupled Reactions -
A chemical reaction having a common intermediate in which energy is transfered from one side of the reaction to the other.
Examples:
1. The formation of ATP is endergonic and is coupled to the creation of a proton gradient.
2. The energy of an exergonic reaction can be used to drive an endergonic reaction
EX: Step 3 of glycolysis yields +3.0 kcal/mol of free energy; Step 4 has a free energy of -9.0. Together = -6.0, so together they are strongly exergonic – energy is released - passed to ATP!
END OF GLYCOLYSIS….
2 ATP’S USED -------- 4 ATP’S 2 net gain
+ 2 NAD+---- 2 NADH and 2 H+
1 GLUCOSE ------ 2 C3H4O3 (PYRUVIC ACID)
Prepartory Conversion Step
Prior to Krebs Citric Acid Cycle
Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the Krebs cycle
MATRIX
NADH
PYRUVATEC-C-C
MITOCHONDRIAL MEMBRANE
Acetyl CoA
CO2
CoA
CoA
MATRIXNAD+
KREB’S CITRIC ACID CYCLE
Figure 9.11 A closer look at the Krebs cycle (Layer 1)
GLYCOLYSISMOVIE
Conversion Thru Krebs
Summary
Figure 9.11 A closer look at the Krebs cycle (Layer 2)
Figure 9.11 A closer look at the Krebs cycle (Layer 3)
Figure 9.11 A closer look at the Krebs cycle (Layer 4)
Figure 9.12 A summary of the Krebs cycle
NET GAIN PER PYRUVATE?
4 NADH
1 FADH2
1 ATP
X 2 TURNS ( 1 PER PYRUVATE)
8 NADH
2 FADH2
2 ATPNET GAIN PER GLUCOSE? - so far….
10 NADH
2 FADH2
4 ATP
WHERE IS THE BIGGEST PART OF THE ENERGY
NOW?
ELECTRONTRANSPORT
SYSTEM
Figure 9.13 Free-energy change during electron transport
Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis
ETS ETS w/ electrons
Proton/ElectronAccounting
Figure 9.14 ATP synthase, a molecular mill
ATP SYNTHASE
WHAT’S HAPPENING?
The Details of ATPSyntase
COMPLETE CATABOLISM OF GLUCOSE REQUIRES 5 STEPS:•GLYCOLYSIS-----GLUCOSE CONVERTED TO PYRUVIC ACID•OXIDATION OF PYRUVIC ACID TO ACETYL CoA•KREB’S CYCLE -CITRIC ACID CYCLE•ELECTRON TRANSPORT CHAIN•CHEMIOSMOSIS
Chemiosmosis-
the phosphorylation of ADP to ATP occurring when protons that are following a concentration gradient
contact ATP synthase.
Oxidative Phosphorylation-
Refers to the coupling of the electron transport chain to ATP synthesis via the proton gradient and ATP
synthase. This occurs primarily in the presence of oxygen.
From glycolysis Protons pumped ATP
2 NADH 8-12* 4-6*
2 ATP (substrate level phosphorylation)
2
From bridge stage
2 NADH 12 6
From citric acid cycle
6 NADH 36 18
2 FADH2 8 4
2 ATP (substrate level phosphorylation)
2
TOTAL 36-38
* The NADH that comes from glycolysis has to
enter the mitochondrion in order to hand its
electrons over to the electron transport
system. There is usually a loss of energy involved in
doing this.
Figure 9.16 Review: how each molecule of glucose yields many ATP molecules during cellular respiration
FERMENTATION
Figure 9.x2 Fermentation
Figure 9.17a Fermentation
IN MOST
PLANTS AND
MANY
MICROBES
Figure 9.17b Fermentation
IN ANIMALS
(MUSCLE)
AND
SOME
MICROBES
• LACTIC ACID AND ALCOHOL ARE STILL RELATIVELY HIGH IN ENERGY.... AND CAN EVENTUALLY UNDERGO AEROBIC RESPIRATION TO RELEASE THIS ENERGY AND CONVERT THEM TO CO2 AND H20.
• THE NET ENERGY YIELD FROM THE ANAEROBIC RESPIRATION OF ONE GLUCOSE MOLECULE IS 2 ATP MOLECULES.
Figure 9.18 Pyruvate as a key juncture in catabolism
Figure 9.19 The catabolism of various food molecules
Figure 9.20 The control of cellular respiration
