Step 1: Understanding the Question:
The question asks for the total number of oxidation steps that occur during a single turn of the Krebs cycle (TCA cycle) in cellular respiration.
Step 2: Key Formula or Approach:
Oxidation in the Krebs cycle is coupled with the reduction of electron carriers. Each time \(NAD^+\) is reduced to \(NADH + H^+\) or \(FAD\) is reduced to \(FADH_2\), an oxidation of the substrate occurs.
Step 3: Detailed Explanation:
In one complete turn of the Krebs cycle, the following four oxidation steps take place:
1. Oxidation of Isocitrate: Isocitrate is oxidized to \(\alpha\)-ketoglutarate, resulting in the reduction of \(NAD^+\) to \(NADH\).
2. Oxidation of \(\alpha\)-ketoglutarate: It is oxidized to Succinyl-CoA, reducing another \(NAD^+\) to \(NADH\).
3. Oxidation of Succinate: Succinate is oxidized to Fumarate, which reduces \(FAD\) to \(FADH_2\).
4. Oxidation of Malate: Malate is oxidized to Oxaloacetate, reducing the third \(NAD^+\) to \(NADH\).
Step 4: Final Answer:
Since there are three steps producing \(NADH\) and one step producing \(FADH_2\), the total number of oxidation events is \(3 + 1 = 4\).
Therefore, oxidation occurs four times in one Krebs cycle.