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