Ageing is due to accumulation of harmful proteins . The theory is

Options

A. Free radical
B. Cross-linking
C. Error catastrophe
D. Cross linking

Answer

### Step-by-Step Solution:

1. **Understanding Aging**: Aging is defined as a physiological process that involves a series of changes in an organism, leading to a decline in physical and biological functions. This process occurs at both cellular and molecular levels and begins in adulthood.

2. **Identifying the Theories**: The question presents three theories regarding aging:
- **Free Radical Theory**: Suggests that aging is caused by damage from reactive oxygen species (ROS).
- **Cross-Linking Theory**: Proposes that aging results from the formation of chemical bonds between protein molecules.
- **Error Catastrophe Theory**: States that aging is due to the accumulation of errors in cellular molecules necessary for cellular function and reproduction, leading to a catastrophic failure of cellular processes.

3. **Evaluating Each Theory**:
- **Free Radical Theory**: While this theory discusses the role of reactive oxygen species in damage accumulation, it does not specifically focus on harmful proteins, making it an incorrect choice for this question.
- **Cross-Linking Theory**: This theory involves the formation of chemical bonds between proteins, which can lead to dysfunction. However, it does not directly address the accumulation of harmful proteins as the primary cause of aging.
- **Error Catastrophe Theory**: This theory aligns with the idea that the accumulation of errors in essential cellular molecules can lead to cellular dysfunction, which is compatible with the concept of harmful proteins accumulating over time.

4. **Conclusion**: Based on the evaluation of the theories, the most appropriate answer to the question is the **Error Catastrophe Theory**, as it connects the accumulation of errors in cellular molecules to the aging process.

### Final Answer:
The theory that best explains aging due to the accumulation of harmful proteins is the **Error Catastrophe Theory**.

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