How many oxidation step take place during glycolysis, link reaction and Kreb's cycle.

Options

A. 1, 1 and 1
B. 1, 1 and 4
C. 1, 1 and 3
D. 1, 1 and 8

Answer

To determine the number of oxidation steps that take place during glycolysis, the link reaction, and the Krebs cycle, we can break down each process step by step.

### Step 1: Glycolysis
- Glycolysis is the first step in cellular respiration that occurs in the cytoplasm.
- It involves the breakdown of one molecule of glucose (a six-carbon compound) into two molecules of pyruvate (three-carbon compounds).
- During glycolysis, there is **one oxidation step** where NAD+ is reduced to NADH. This occurs when a hydrogen atom is removed from the substrate (glucose) and transferred to NAD+.

### Step 2: Link Reaction
- The link reaction occurs in the mitochondria and converts pyruvate into acetyl-CoA.
- In this process, each pyruvate (three-carbon) is converted into acetyl-CoA (two-carbon) and releases one molecule of carbon dioxide.
- During this conversion, there is **one oxidation step** where NAD+ is again reduced to NADH by removing a hydrogen atom from pyruvate.

### Step 3: Krebs Cycle (Citric Acid Cycle)
- The Krebs cycle occurs in the mitochondrial matrix and involves a series of reactions that further oxidize acetyl-CoA.
- For each acetyl-CoA that enters the cycle, there are **four oxidation steps** where NAD+ is reduced to NADH. This happens at different points in the cycle as carbon compounds are oxidized.

### Total Oxidation Steps
- Glycolysis: 1 oxidation step
- Link Reaction: 1 oxidation step
- Krebs Cycle: 4 oxidation steps

Adding these together:
1 (glycolysis) + 1 (link reaction) + 4 (Krebs cycle) = **6 oxidation steps in total**.

### Final Answer
The total number of oxidation steps that take place during glycolysis, the link reaction, and the Krebs cycle is **6**.

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