Which of the following steps in cellular respiration is associated with release of maximum number of ATP molecules?

Options

A. Glycolysis
B. Kreb's cycle
C. Oxidative phosphorylation
D. Reduction of NADP

Explanation

To determine which step in cellular respiration is associated with the release of the maximum number of ATP molecules, we can analyze the different stages of the process:

1. **Glycolysis**: This is the first step of cellular respiration where glucose is broken down into pyruvate. During glycolysis, a net gain of 2 ATP molecules is produced.

2. **Krebs Cycle (Citric Acid Cycle)**: In this cycle, acetyl-CoA is converted into oxaloacetic acid, and through a series of reactions, 2 ATP molecules are produced per cycle. However, since each glucose molecule results in two acetyl-CoA molecules, the total ATP yield from the Krebs cycle is 2 ATP per glucose.

3. **Oxidative Phosphorylation**: This is the final step of cellular respiration, which occurs in the mitochondria. It involves the electron transport chain and chemiosmosis, where a significant amount of ATP is produced. The yield from this process is approximately 24 to 28 ATP molecules, depending on the efficiency of the electron transport chain and the conditions within the cell.

4. **Reduction of NADP**: This step does not produce ATP; instead, it involves the reduction of NADP+ to NADPH, which is important for other metabolic processes.

After analyzing these steps, we can conclude that the step associated with the release of the maximum number of ATP molecules is **Oxidative Phosphorylation**, which produces 24 to 28 ATP molecules.

**Final Answer**: The step in cellular respiration associated with the release of the maximum number of ATP molecules is **Oxidative Phosphorylation**.

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