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 can break down the process into its key components:

### Step-by-Step Solution:

1. **Glycolysis**:
- The first stage of aerobic respiration is glycolysis. This process occurs in the cytoplasm of the cell and involves the breakdown of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon compound). During glycolysis, a small amount of ATP is produced, and NADH (an electron carrier) is generated.

2. **Krebs Cycle (Citric Acid Cycle)**:
- After glycolysis, the pyruvate produced enters the mitochondria, where it undergoes further breakdown in the Krebs cycle, also known as the citric acid cycle. In this cycle, pyruvate is converted into acetyl-CoA, which then enters a series of reactions that produce more NADH and FADH2 (another electron carrier), as well as a small amount of ATP. Carbon dioxide is released as a byproduct.

3. **Electron Transport Chain (ETC)**:
- The final stage of aerobic respiration is the electron transport chain, which takes place in the inner mitochondrial membrane. Here, the NADH and FADH2 produced in the previous stages donate electrons to the chain, leading to the transfer of protons across the membrane. This creates a proton gradient that drives the synthesis of a large amount of ATP through a process called oxidative phosphorylation. Oxygen serves as the final electron acceptor, forming water.

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

### Final Answer:
The correct order is: Glycolysis → Krebs Cycle → Electron Transport Chain.

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