Which of the following sets consists only of essential amino acids ?

Options

A. Alanine, tyrosine, cysteine
B. Leucine, lysine , tryptophan
C. Alanine , glutamine ,lysine
D. Leucine, proline, glycine

Answer

To determine which set consists only of essential amino acids, we first need to understand the classification of amino acids. Amino acids can be categorized into three types:

1. **Essential Amino Acids**: These are amino acids that the body cannot synthesize on its own and must be obtained from the diet.
2. **Non-Essential Amino Acids**: These amino acids can be synthesized by the body.
3. **Conditionally Essential Amino Acids**: These amino acids are usually non-essential but become essential under certain conditions, such as illness or stress.

Now, let's analyze the given sets of amino acids one by one to identify which set contains only essential amino acids.

### Step 1: Analyze the first set
- **Set 1**: Alanine, Tyrosine, Cysteine
- **Alanine**: Non-essential (can be synthesized by the body)
- **Tyrosine**: Non-essential (can be synthesized by the body)
- **Cysteine**: Conditionally essential (generally non-essential but essential during illness)

This set does not consist of only essential amino acids.

### Step 2: Analyze the second set
- **Set 2**: Leucine, Lysine, Tryptophan
- **Leucine**: Essential
- **Lysine**: Essential
- **Tryptophan**: Essential

This set consists only of essential amino acids.

### Step 3: Analyze the third set
- **Set 3**: Alanine, Glutamine, Lysine
- **Alanine**: Non-essential
- **Glutamine**: Conditionally essential
- **Lysine**: Essential

This set does not consist of only essential amino acids.

### Step 4: Analyze the fourth set
- **Set 4**: Leucine, Proline, Glycine
- **Leucine**: Essential
- **Proline**: Conditionally essential
- **Glycine**: Non-essential

This set does not consist of only essential amino acids.

### Conclusion
The only set that consists entirely of essential amino acids is **Set 2: Leucine, Lysine, and Tryptophan**.