Final answer:
In the citric acid cycle, there are four oxidation-reduction steps. These steps are crucial for the conversion of energy from acetyl-CoA. NAD+ and FAD are the coenzymes reduced to NADH and FADH2 during these steps.
Step-by-step explanation:
The citric acid cycle, also known as the Krebs cycle or the tricarboxylic acid (TCA) cycle, involves multiple steps where oxidation-reduction reactions occur. In the cycle, there are a total of four points where oxidation-reduction (redox) reactions take place:
- Step 3: Isocitrate is oxidized to α-ketoglutarate, and NAD+ is reduced to NADH.
- Step 4: α-Ketoglutarate undergoes oxidative decarboxylation to form succinyl-CoA, and NAD+ is reduced to NADH.
- Step 6: Succinate is oxidized to fumarate, and FAD is reduced to FADH2.
- Step 8: The oxidation of malate to oxaloacetate, with the reduction of NAD+ to NADH.
These redox steps are essential for the citric acid cycle to extract energy from the acetyl group of acetyl-CoA and are integral in the overall process of cellular respiration.