Essential-non-essential amino acid is

Options

A. Lysine - Leucine
B. Valine - Tyrosine
C. Methionine - Threonine
D. Alanine - Cystine.

Answer

To determine which pair consists of one essential amino acid and one non-essential amino acid, we will categorize the given amino acids based on their classification.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Essential Amino Acids**: These amino acids cannot be synthesized by the body and must be obtained through diet.
- **Non-Essential Amino Acids**: These amino acids can be synthesized by the body, so they do not need to be obtained from the diet.

2. **List the Given Amino Acids**:
- Lysine
- Leucine
- Valine
- Tyrosine
- Methionine
- Threonine
- Alanine
- Cysteine

3. **Categorize Each Amino Acid**:
- **Essential Amino Acids**:
- Lysine
- Leucine
- Valine
- Methionine
- Threonine
- **Non-Essential Amino Acids**:
- Tyrosine
- Alanine
- Cysteine

4. **Evaluate Each Pair**:
- **Lysine and Leucine**: Both are essential (incorrect).
- **Leucine and Valine**: Both are essential (incorrect).
- **Valine and Tyrosine**: Valine is essential, Tyrosine is non-essential (correct).
- **Methionine and Threonine**: Both are essential (incorrect).
- **Alanine and Cysteine**: Both are non-essential (incorrect).

5. **Identify the Correct Pair**:
- The only pair that consists of one essential and one non-essential amino acid is **Valine (essential) and Tyrosine (non-essential)**.

### Conclusion:
The correct answer is the pair **Valine and Tyrosine**.

---