Cofactors are

Options

A. non-protein organic molecules
B. vitamins
C. metallic ions
D. all of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Cofactors**: Cofactors are non-protein chemical compounds that are essential for the activity of certain enzymes. They can be either organic molecules or inorganic ions.

2. **Types of Cofactors**:
- **Organic Cofactors**: These are often referred to as coenzymes and include vitamins. They assist in enzyme activity by providing additional functional groups that are necessary for the reaction.
- **Inorganic Cofactors**: These are typically metallic ions such as zinc, magnesium, iron, and copper. They play a crucial role in stabilizing enzyme structures and facilitating the biochemical reactions.

3. **Function of Cofactors**: Cofactors assist enzymes in catalyzing biochemical reactions. They can help in the binding of substrates to the enzyme, stabilizing the enzyme-substrate complex, and participating directly in the chemical reaction.

4. **Analyzing the Options**: The question provides multiple choices:
- Non-protein organic molecules (like vitamins)
- Metallic ions
- All of the above

5. **Correct Answer**: Since cofactors can be both organic molecules (like vitamins) and metallic ions, the correct answer is "All of the above."

**Final Answer**: Cofactors are non-protein organic molecules, vitamins, metallic ions, and all of the above.

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