DAT Biology: Cellular Metabolism 3

Question 1

The pyruvate dehydrogenase complex converts pyruvate into which molecule entering the citric acid cycle?

Accepted Answer

Acetyl-CoA

Answer

Pyruvate is oxidatively decarboxylated to acetyl-CoA, releasing CO2 and producing NADH.

Question 2

How many CO2 molecules are released per turn of the citric acid cycle?

Accepted Answer

2

Answer

Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase each release one CO2 per turn.

Question 3

Which molecule combines with acetyl-CoA to form citrate?

Accepted Answer

Oxaloacetate

Answer

Citrate synthase condenses acetyl-CoA with oxaloacetate to begin the cycle.

Question 4

Per turn of the citric acid cycle, how many NADH molecules are produced?

Accepted Answer

3

Answer

Three NADH are generated at the isocitrate, alpha-ketoglutarate, and malate dehydrogenase steps.

Question 5

Which high-energy molecule is produced directly by substrate-level phosphorylation in the citric acid cycle?

Accepted Answer

GTP

Answer

Succinyl-CoA synthetase produces GTP (or ATP) by substrate-level phosphorylation.

DAT Practice Test