Photosynthesis Cellular Respiration 2

Question 1

Which molecule serves as the primary electron carrier in the electron transport chain during cellular respiration?

Accepted Answer

NADH

Answer

NADH donates electrons to Complex I of the electron transport chain, driving the proton gradient used for ATP synthesis.

Question 2

At which pH range does the intermembrane space of the mitochondria sit during active cellular respiration?

Accepted Answer

Around pH 4–5

Answer

Protons pumped into the intermembrane space by the ETC complexes make it more acidic, roughly pH 4–5.

Question 3

How many ATP molecules are produced per FADH2 via oxidative phosphorylation?

Accepted Answer

~1.5 ATP

Answer

FADH2 enters the ETC at Complex II, bypassing Complex I, so it yields approximately 1.5 ATP compared to NADH's ~2.5 ATP.

Question 4

What happens to pyruvate when oxygen is unavailable in human muscle cells?

Accepted Answer

It is converted to lactate

Answer

In oxygen-deprived human muscle cells, pyruvate accepts electrons from NADH and is reduced to lactate, regenerating NAD+.

Question 5

Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA?

Accepted Answer

Pyruvate dehydrogenase complex

Answer

The pyruvate dehydrogenase complex oxidatively decarboxylates pyruvate, producing acetyl-CoA, CO2, and NADH.

Photosynthesis Practice Test