A: Coenzymes are usually proteins
R:The term feedback refers to the effect of enzyme concentration on its rate of reaction.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

To analyze the assertion and reason provided in the question, we will evaluate each statement step by step.

### Step 1: Evaluate the Assertion
- **Assertion**: "Coenzymes are usually proteins."
- Coenzymes are indeed important for enzyme function, but they are not proteins themselves. Instead, they are organic molecules that often derive from vitamins (e.g., B vitamins). They assist enzymes in catalyzing reactions but do not have a protein structure. Therefore, this assertion is **false**.

### Step 2: Evaluate the Reason
- **Reason**: "The term feedback refers to the effect of enzyme concentration on its rate of reaction."
- The term "feedback" in biochemistry typically refers to feedback inhibition, where the end product of a metabolic pathway inhibits an earlier step in the pathway. It does not specifically refer to the effect of enzyme concentration on the rate of reaction. Instead, the rate of reaction is influenced by enzyme concentration, but feedback is more about the regulation of enzyme activity based on product levels. Thus, this reason is also **false**.

### Step 3: Conclusion
- Both the assertion and the reason are false. Therefore, the correct answer to the question is that both statements are incorrect.

### Final Answer:
Both the assertion and reason are false.

---