Biochemistry Lecture 10
Only a Small Amount of Energy Available in Glucose is Captured in Glycolysis 2 G’° = -146 kJ/mol Glycolysis Full oxidation (+ 6 O 2 ) G’° = -2,840 kJ/mol 6 CO H 2 O GLUCOSE
Cellular Respiration: the big picture process in which cells consume O 2 and produce CO 2 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
Stage 1. Acetyl-CoA production
Stage 2. Acetyl-CoA Oxidation
Stage 3. Electron Transfer and oxidative Phosphorylation
Where does this all happen?
Stage 1. Acetyl-CoA production
Pyruvate Decarboxylation
The PDC
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
Structure of CoA
Stage 2. Acetyl-CoA Oxidation
Step 1
Step 2
Sterospecificity
Step 3
Step 4
Step 5.
Succinyl-CoA Succinate Succinyl-CoA Synthetase Succinate dehydrogenase * * Carbons are scrambled at succinate * 1/2
Step 6.
Step 7.
Products from one turn of the cycle
Net Effect of the Citric Acid Cycle Acetyl-CoA + 3NAD + + FAD + GDP + P i + 2 H 2 O 2CO 2 +3NADH + FADH 2 + GTP + CoA + 3H + carbons of acetyl groups in acetyl-CoA are oxidized to CO 2 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
Energy Yield