Biochemistry Lecture 13. Only a Small Amount of Energy Available in Glucose is Captured in...
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Transcript of Biochemistry Lecture 13. Only a Small Amount of Energy Available in Glucose is Captured in...
Only a Small Amount of Energy Available in Glucose
is Captured in Glycolysis
2G’° = -146 kJ/mol
Glycolysis
Full oxidation (+ 6 O2)
G’° = -2,840 kJ/mol6 CO2 + 6 H2O
GLUCOSE
Cellular Respiration: the big picture
• process in which cells consume O2 and produce CO2
• provides more energy (ATP) from glucose than glycolysis
• also captures energy stored in lipids and amino acids
• evolutionary origin: developed about 2.5 billion years ago
• used by animals, plants, and many microorganisms
• occurs in three major stages:
- acetyl CoA production
- acetyl CoA oxidation
- electron transfer and oxidative phosphorylation
Sequence of Events in Pyruvate
Decarboxylation• Step 1: Decarboxylation of pyruvate to an aldehyde
• Step 2: Oxidation of aldehyde to a carboxylic acid
• Step 3: Formation of acetyl CoA
• Step 4: Reoxidation of the lipoamide cofactor
• Step 5: Regeneration of the oxidized FAD cofactor
Succinyl-CoA
Succinate
Succinyl-CoA Synthetase
Succinate dehydrogenase
*
*
Carbons are scrambled at succinate
*
1/2
1/2
Net Effect of the Citric Acid Cycle
Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2 H2O
2CO2 +3NADH + FADH2 + GTP + CoA + 3H+
• carbons of acetyl groups in acetyl-CoA are
oxidized to CO2
• electrons from this process reduce NAD+ and FAD
• one GTP is formed per cycle, this can be
converted to ATP
• intermediates in the cycle are not depleted