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 first need to identify which of the listed amino acids are considered essential.

### Step-by-Step Solution:

1. **Understand Essential Amino Acids**: Essential amino acids are those that the human body cannot synthesize on its own and must be obtained through diet. There are nine essential amino acids that are generally recognized.

2. **List of Essential Amino Acids**: The nine essential amino acids are:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine

3. **Identify the Given Amino Acids**: The amino acids provided in the question are:
- Histidine
- Glycine
- Valine
- Alanine
- Aspartic acid
- Lysine
- Methionine

4. **Check Each Amino Acid Against the Essential List**:
- Histidine: Essential
- Glycine: Non-essential
- Valine: Essential
- Alanine: Non-essential
- Aspartic acid: Non-essential
- Lysine: Essential
- Methionine: Essential

5. **Count the Essential Amino Acids**: From the above checks, the essential amino acids in the list are:
- Histidine
- Valine
- Lysine
- Methionine

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

### Final Answer:
The number of essential amino acids among the given options is **4**.

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