How many different tripeptides can be obtained from alanine, glycine and phenylalanine, each tripeptide containing all the three amino acids?

Answer

To determine how many different tripeptides can be formed from the amino acids alanine (A), glycine (G), and phenylalanine (F), we can follow these steps:

### Step 1: Understand the Concept of Tripeptides
A tripeptide consists of three amino acids linked together by peptide bonds. In this case, we are using three different amino acids: alanine, glycine, and phenylalanine.

### Step 2: Determine the Arrangement of Amino Acids
Since we need to form a tripeptide using all three amino acids, we need to find out how many different ways we can arrange these three amino acids.

### Step 3: Calculate the Permutations
The number of different arrangements (permutations) of n distinct items is given by the formula n!. Here, n = 3 (the three amino acids: A, G, F).

So, we calculate:
\[ 3! = 3 \times 2 \times 1 = 6 \]

### Step 4: List the Possible Tripeptides
The different arrangements of alanine (A), glycine (G), and phenylalanine (F) are:
1. A-G-F
2. A-F-G
3. G-A-F
4. G-F-A
5. F-A-G
6. F-G-A

### Conclusion
Thus, the total number of different tripeptides that can be formed from alanine, glycine, and phenylalanine is **6**.

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