The number of essential amino acids among the following is ..........
Histidine, Glycine, valine , Alanine, Aspartic acid, Lysine, methionine.

Answer

To determine the number of essential amino acids from the given list, we need to identify which of the amino acids cannot be synthesized by the human body and must be obtained through diet.

1. **List the given amino acids**:
- Histidine
- Glycine
- Valine
- Alanine
- Aspartic acid
- Lysine
- Methionine

2. **Identify essential amino acids**:
Essential amino acids are those that the body cannot produce on its own. The essential amino acids are:
- Phenylalanine
- Threonine
- Methionine
- Valine
- Tryptophan
- Leucine
- Isoleucine
- Lysine
- Histidine
- Arginine (conditionally essential)

3. **Check each amino acid from the list**:
- **Histidine**: Essential
- **Glycine**: Not essential
- **Valine**: Essential
- **Alanine**: Not essential
- **Aspartic acid**: Not essential
- **Lysine**: Essential
- **Methionine**: Essential

4. **Count the essential amino acids**:
From the list, the essential amino acids are:
- Histidine
- Valine
- Lysine
- Methionine

Therefore, there are a total of **4 essential amino acids** in the provided list.

**Final Answer**: The number of essential amino acids among the following is **4**.

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