Which element is present in two amino acids, cysteine and methionine, and is the main constituent of several coenzymes, vitamins (thiamine, biotin) and ferredoxin.

Options

A. Sulphur
B. Boron
C. Molybdenum
D. Copper

Explanation

To solve the question regarding which element is present in the amino acids cysteine and methionine, and is also a main constituent of several coenzymes and vitamins, we can follow these steps:

### Step 1: Identify the Amino Acids
The question mentions two specific amino acids: cysteine and methionine.

### Step 2: Determine the Elements in the Amino Acids
Both cysteine and methionine are known to contain sulfur in their molecular structure.

### Step 3: Analyze the Coenzymes and Vitamins
Next, we need to consider the other components mentioned in the question: coenzymes, vitamins (thiamine and biotin), and ferredoxin.

- **Coenzymes**: For example, coenzyme A contains sulfur.
- **Vitamins**: Thiamine (Vitamin B1) and biotin (Vitamin B7) also include sulfur in their structure.
- **Ferredoxin**: This is a protein that contains iron and sulfur clusters.

### Step 4: Compare with Other Options
The question provides four options: sulfur, boron, molybdenum, and copper. We need to determine if any of these elements are present in cysteine, methionine, and the mentioned coenzymes and vitamins.

- **Boron**: Not known to be present in cysteine or methionine.
- **Molybdenum**: Not associated with cysteine or methionine.
- **Copper**: Also not present in cysteine or methionine.

### Step 5: Conclusion
Based on the analysis, the only element that is present in both cysteine and methionine, and is also a significant component of coenzymes, vitamins, and ferredoxin is sulfur.

### Final Answer
The answer to the question is **sulfur**.

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