Two of the following amino are needed for growth only and are not essential for adults.

Options

A. Cysteine and cystine
B. Lecucine and Valine
C. Tryptophan and isolecucine
D. Arginine and histidine

Answer

To answer the question regarding which two amino acids are needed for growth but are not essential for adults, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Classification of Amino Acids**:
- Amino acids are classified into two categories: essential and non-essential.
- Essential amino acids cannot be synthesized by the body and must be obtained through diet.
- Non-essential amino acids can be synthesized by the body.

2. **Identify Essential Amino Acids**:
- List the essential amino acids: phenylalanine, valine, threonine, leucine, isoleucine, lysine, and histidine.
- These amino acids are crucial for adults and must be obtained from food sources.

3. **Identify Non-Essential Amino Acids**:
- List the non-essential amino acids: arginine, cysteine, glycine, glutamine, proline, and tyrosine.
- These amino acids can be produced by the body and are not required to be consumed in the diet.

4. **Select Amino Acids Needed for Growth**:
- Among the non-essential amino acids, identify those that are particularly important for growth.
- Arginine and proline are two amino acids that play significant roles in growth and development.

5. **Conclusion**:
- The two amino acids that are needed for growth but are not essential for adults are **arginine** and **proline**.

### Final Answer:
The two amino acids needed for growth only and are not essential for adults are **arginine** and **proline**.

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