Question

Part A Calculate the maximum theoretical ATP yields for the complete oxidation of

1) one lactate

2) one glyceraldehyde-3-phosphate

Remember that any intermediate generated (like a pyruvate from lactate oxidation) can then go through it's normal pathway(s) (e.g., pyruvate decarboxylation).

Part B: Write the balanced equation for ethanol fermentation in yeast including ATP, NADH....

Part C: What is the disadvantage of using iron or sulfur as a terminal electron acceptor over oxygen in organisms that do anaerobic respiration? Explain mathematically (with an equation) if possible.

Answer 1

1. Lactate is converted to pyruvate by lactate dehydrogenase.
Lactate + NAD+ -------> Pyruvate + NADH

Pyruvate is converted to acetyl CoA by Pyruvate dehydrogenase.
Pyruvate + CoASH + NAD+ -----> Acetyl CoA + CO2 + NADH

Acetyl CoA enters the TCA cycle to produce CO2 and H2O.
Acetyl CoA + 3 NAD+ + 1 FAD + 1 ADP + Pi ------> 2 CO2 + 3 NADH + 1 FADH2 + 1 ATP

1 NADH = 2.5 ATP
1 FADH2 = 1.5 ATP
Net ATP yiled = (5*2.5)+(1*1.5)+1
= 15 ATP

2. G-3-P is converted to pyruvate via glycolytic pathway.
G-3-P + NAD+ + 2 ADP + 2 Pi -----> Pyruvate + NADH + 2 ATP

Pyruvate is converted to acetyl CoA by Pyruvate dehydrogenase.
Pyruvate + CoASH + NAD+ -----> Acetyl CoA + CO2 + NADH

Acetyl CoA enters the TCA cycle to produce CO2 and H2O.
Acetyl CoA + 3 NAD+ + 1 FAD + 1 ADP + Pi ------> 2 CO2 + 3 NADH + 1 FADH2 + 1 ATP

1 NADH = 2.5 ATP
1 FADH2 = 1.5 ATP
Net ATP yiled = (6*2.5)+(1*1.5)+3
= 19.5 ATP