Function of electron transport chain in both mitochondria and chloroplasts is to develop

Options

A. Mineral gradient
B. Proton gradient
C. Aqueous gradient
D. Protein gradient.

Answer

### Step-by-Step Solution:

1. **Understanding the Electron Transport Chain (ETC)**:
- The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane in mitochondria and in the thylakoid membrane of chloroplasts.
- Its primary function is to transfer electrons derived from nutrients (in mitochondria) or light energy (in chloroplasts) through a series of redox reactions.

2. **Role of Redox Reactions**:
- As electrons are passed along the chain, they undergo oxidation and reduction reactions (redox reactions).
- These reactions release energy, which is used to pump protons (H⁺ ions) across the membrane.

3. **Development of Proton Gradient**:
- The pumping of protons creates a concentration gradient across the membrane, known as the proton electrochemical gradient.
- This gradient represents potential energy, which can be harnessed to perform work.

4. **Synthesis of ATP**:
- The proton gradient created by the electron transport chain drives the synthesis of ATP through a process called chemiosmosis.
- Protons flow back into the mitochondrial matrix or chloroplast stroma through ATP synthase, a protein complex that synthesizes ATP from ADP and inorganic phosphate.

5. **Final Electron Acceptor**:
- In aerobic respiration, the final electron acceptor in the electron transport chain is oxygen.
- This is crucial because it allows for the continuation of the electron transport process and the maintenance of the proton gradient.

6. **Conclusion**:
- Therefore, the primary function of the electron transport chain in both mitochondria and chloroplasts is to develop a proton gradient, which is essential for ATP synthesis.

### Final Answer:
The function of the electron transport chain in both mitochondria and chloroplasts is to develop a **proton gradient**.

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