Examine the figure above depicting the preparatory step and the Krebs cycle, and identify statements that correctly describe these processes.

Question

Select all statements that correctly describe the preparatory step and the Krebs cycle.
View Available Hint(s)for Part E

The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process.
There are five oxidation-reduction reactions depicted.
CO2 serves as the electron acceptor.
It takes two “turns” of the Krebs cycle to process the pyruvic acid molecules resulting from the glycolysis of one glucose molecule.
The equivalent of one ATP is made for each turn of the Krebs cycle.
This process occurs in mitochondria in both eukaryotes and prokaryotes.
The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD.
Carbons from pyruvic acid end up as CO2.

Answer 1

Based on the processes of the preparatory step and the Krebs cycle, the following statements correctly describe these processes:

1. The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process. - This is true as oxaloacetate is regenerated after each cycle.

2. It takes two “turns” of the Krebs cycle to process the pyruvic acid molecules resulting from the glycolysis of one glucose molecule. - This is correct, as one glucose molecule produces two pyruvate molecules, requiring two turns of the cycle.

3. The equivalent of one ATP is made for each turn of the Krebs cycle. - Correct, as one ATP (or its equivalent in GTP) is produced for each cycle turn.

4. The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD. - True, as during the conversion of pyruvate and throughout the Krebs cycle, energy is captured in NADH and FADH₂.

5. Carbons from pyruvic acid end up as CO2. - This is true, as during the Krebs cycle, the carbons of pyruvate are released as carbon dioxide.

The other statements are either incorrect or misleading:

• There are five oxidation-reduction reactions depicted. - This statement may not be correct in a general sense as the exact number of such reactions can vary based on the specific representation or diagram being referenced.

• CO2 serves as the electron acceptor. - This is incorrect. CO2 is a product of the cycle, not an electron acceptor. The primary electron acceptors are NAD+ and FAD.

• This process occurs in mitochondria in both eukaryotes and prokaryotes. - This is not correct. While it occurs in the mitochondria of eukaryotes, prokaryotes lack mitochondria; instead, cellular respiration takes place in the cytoplasm or across the plasma membrane.

In summary, the correct statements are:

• The oxaloacetic acid that accepts the acetyl group is regenerated, enabling the cyclic nature of this process.
• It takes two “turns” of the Krebs cycle to process the pyruvic acid molecules resulting from the glycolysis of one glucose molecule.
• The equivalent of one ATP is made for each turn of the Krebs cycle.
• The potential energy in the pyruvate is transferred to coenzymes NAD+ and FAD.
• Carbons from pyruvic acid end up as CO2.