How many among the given amino are essential and must be obtained from food?
Phenylalanine
Valine
Leucine
Glycine
Isoleucine
Threonine
Aspartic acid
(a) 4
(b) 5
(c) 6
(d) 7

Options

A. 4
B. 5
C. 6
D. 7

Answer

To determine how many of the given amino acids are essential and must be obtained from food, we can follow these steps:

### Step 1: Understand the Concept of Essential Amino Acids
Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet. There are a total of 20 amino acids, out of which 9 are classified as essential.

### Step 2: List the Given Amino Acids
The amino acids provided in the question are:
- Phenylalanine
- Valine
- Leucine
- Glycine
- Isoleucine
- Threonine
- Aspartic acid

### Step 3: Identify Which of These Amino Acids are Essential
From the list of essential amino acids, we know they include:
1. Phenylalanine
2. Valine
3. Leucine
4. Isoleucine
5. Threonine
6. Lysine
7. Methionine
8. Histidine
9. Tryptophan

Now, we will check each of the given amino acids against this list:
- **Phenylalanine**: Essential
- **Valine**: Essential
- **Leucine**: Essential
- **Glycine**: Not essential (it is a non-essential amino acid)
- **Isoleucine**: Essential
- **Threonine**: Essential
- **Aspartic acid**: Not essential (it is a non-essential amino acid)

### Step 4: Count the Essential Amino Acids
From the analysis, we find the following essential amino acids from the given list:
1. Phenylalanine
2. Valine
3. Leucine
4. Isoleucine
5. Threonine

This gives us a total of **5 essential amino acids**.

### Conclusion
The answer to the question is **(b) 5**.

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