Which of the following is a biological uncoupler of oxidative phosphorylation

Options

A. Thermogenin
B. 2, 4-Dichlorophenoxyacetic acid
C. 2, 4-Dinitrophenol
D. Ethylene diaminotetra-acetic acid.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a biological uncoupler of oxidative phosphorylation. Oxidative phosphorylation is a process that occurs in the mitochondria, where ATP is produced using the energy from electrons transferred through the electron transport chain.

2. **Identifying the Options**: The options given are:
- Thermogenin
- 2,4-dichlorophenoxyacetic acid
- 2,4-dinitrophenol
- Ethylene diaminotetraacetic acid

3. **Defining Biological Uncouplers**: Biological uncouplers are substances that disrupt the coupling between the electron transport chain and ATP synthesis. They allow protons to flow back into the mitochondrial matrix without generating ATP, thus "uncoupling" the processes.

4. **Analyzing Each Option**:
- **Thermogenin**: This is known as an uncoupling protein found in the inner mitochondrial membrane. It increases the permeability of the membrane to protons, allowing them to return to the matrix without generating ATP. This process generates heat instead of ATP, which is important for thermoregulation in certain organisms.
- **2,4-dichlorophenoxyacetic acid**: This is a herbicide and does not function as an uncoupler.
- **2,4-dinitrophenol**: This is a chemical that acts as a protonophore, allowing protons to cross the mitochondrial membrane and thus uncoupling oxidative phosphorylation. However, it is not a biological uncoupler in the same sense as thermogenin.
- **Ethylene diaminotetraacetic acid (EDTA)**: This is a chelating agent and does not act as an uncoupler.

5. **Conclusion**: Among the options, thermogenin is the only biological uncoupler of oxidative phosphorylation.

**Final Answer**: The biological uncoupler of oxidative phosphorylation is **thermogenin**.

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