Which statement regarding coenzyme is incorrect ?

Options

A. Every cofactor is a coenzyme and every coenzyme is a cofactor
B. Every coenzyme is a cofactor but every cofactor is not coenzyme
C. Most of the coenzymes are nucleotides and are composed of two vitamins
D. Coenzymes are thee active constituents of enzymes

Answer

To determine which statement regarding coenzymes is incorrect, we need to analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Understanding Coenzymes and Cofactors**:
- **Cofactors** are non-protein chemical compounds that are required for the biological activity of some proteins, typically enzymes.
- **Coenzymes** are a specific type of cofactor that are organic molecules, often derived from vitamins.

2. **Analyzing the Statements**:
- **Statement 1**: "Every cofactor is a coenzyme."
- This statement is incorrect because not all cofactors are coenzymes. Cofactors can also include metal ions and prosthetic groups, which are not classified as coenzymes.

- **Statement 2**: "Every coenzyme is a cofactor."
- This statement is correct. All coenzymes are indeed a type of cofactor.

- **Statement 3**: "Most of the enzymes are nucleotides and are composed of two vitamins."
- This statement is misleading. While some coenzymes are derived from vitamins, enzymes themselves are primarily proteins, not nucleotides.

- **Statement 4**: "Coenzymes are the active constituents of enzymes."
- This statement is misleading. Coenzymes assist enzymes but are not the active site themselves; they are transiently associated with the enzyme to aid in its function.

3. **Conclusion**:
- The incorrect statement regarding coenzymes is **Statement 1**: "Every cofactor is a coenzyme."

### Final Answer:
The incorrect statement regarding coenzymes is: **"Every cofactor is a coenzyme."**