Essential amino acids are those which our body can not synthesize and, therefore, we take them from diet . These are usually seven in number and are .

Options

A. leucine, lysine, isoleucine ,valine , tryptophan, phenylalanine , methionine
B. leucine-lysin-isoleucine-valine-tryptophan-phenylalanine -glycine.
C. gly-ala-val-his-try-asp-met
D. none of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Essential Amino Acids**: Essential amino acids are those that the human body cannot synthesize on its own. This means we must obtain them through our diet.

2. **Identifying the Number of Essential Amino Acids**: There are usually nine essential amino acids recognized in human nutrition, but the question specifies a common grouping of seven.

3. **Listing the Seven Essential Amino Acids**:
- **Leucine**: Important for protein synthesis and muscle repair.
- **Lysine**: Plays a crucial role in protein synthesis, hormone production, and calcium absorption.
- **Isoleucine**: Involved in muscle metabolism and is heavily concentrated in muscle tissue.
- **Valine**: Important for energy production and muscle metabolism.
- **Tryptophan**: A precursor for serotonin, which regulates mood and sleep.
- **Phenylalanine**: A precursor for neurotransmitters and important for the production of other amino acids.
- **Methionine**: Plays a role in metabolism and detoxification.

4. **Including Additional Essential Amino Acids**: Besides the common seven, two more amino acids are often considered essential:
- **Histidine**: Important for growth and tissue repair.
- **Threonine**: Important for protein synthesis and immune function.

5. **Conclusion**: The essential amino acids that must be obtained from the diet are leucine, lysine, isoleucine, valine, tryptophan, phenylalanine, methionine, histidine, and threonine.

**Final List of Essential Amino Acids**:
1. Leucine
2. Lysine
3. Isoleucine
4. Valine
5. Tryptophan
6. Phenylalanine
7. Methionine
8. Histidine
9. Threonine

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