What is the correct order of the stages during aerobic respiration ?

Options

A. Kreb's cycle - Electron transport chain - Glycolysis
B. Electron transport chain- Kreb’s cycle - Glycolysis
C. Glycolysis - Krebs’ cycle - Electron transport chain
D. Glycolysis -Electron transport chain Krebs’ cycle

Answer

To determine the correct order of the stages during aerobic respiration, we need to understand the sequence of processes involved in the breakdown of glucose to produce ATP. Here’s a step-by-step breakdown of the stages:

### Step 1: Glycolysis
- **Description**: Glycolysis is the first stage of aerobic respiration. It occurs in the cytoplasm of the cell and involves the breakdown of one molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon compound).
- **Products**: This process generates a small amount of ATP (net gain of 2 ATP) and reduces NAD+ to NADH.

### Step 2: Krebs Cycle (Citric Acid Cycle)
- **Description**: After glycolysis, the pyruvate molecules are transported into the mitochondria where they are converted into acetyl coenzyme A. This acetyl CoA then enters the Krebs cycle.
- **Products**: The Krebs cycle involves a series of enzymatic reactions that produce ATP, NADH, FADH2, and carbon dioxide (CO2) as a byproduct. This cycle is crucial for further oxidation of the carbon skeleton.

### Step 3: Electron Transport Chain (ETC)
- **Description**: The NADH and FADH2 produced in the Krebs cycle are then used in the electron transport chain, which takes place in the inner mitochondrial membrane.
- **Products**: In the ETC, electrons are transferred through a series of proteins, leading to the production of a large amount of ATP (approximately 34 ATP molecules) via oxidative phosphorylation. Water is formed as a byproduct when electrons combine with oxygen.

### Conclusion
The correct order of the stages during aerobic respiration is:
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain

Thus, the correct answer is **Option C: Glycolysis, Krebs Cycle, Electron Transport Chain**.

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