A protein has how many terminal amino acids and are called________?

Options

A. 2, N-terminal amino acid and C-terminal amino acid
B. 3, N-terminal amino acid, C-terminal amino acid, R-terminal amino acid
C. 1, C-terminal amino acid
D. 4, N-terminal amino acids

Answer

To answer the question about how many terminal amino acids are present in a protein and what they are called, follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of Proteins**:
- Proteins are made up of long chains of amino acids, known as polypeptides. Each polypeptide has a specific sequence of amino acids.

2. **Identifying Terminal Amino Acids**:
- In a polypeptide chain, there are two ends: one end is called the N-terminus and the other end is called the C-terminus.

3. **N-terminal Amino Acid**:
- The N-terminal amino acid is the first amino acid in the sequence. It has a free amino group (-NH2) at one end, which is why it is referred to as the N-terminal.

4. **C-terminal Amino Acid**:
- The C-terminal amino acid is the last amino acid in the sequence. It has a free carboxyl group (-COOH) at the other end, which is why it is referred to as the C-terminal.

5. **Conclusion**:
- Therefore, a protein has **two terminal amino acids**: the N-terminal and the C-terminal.

6. **Final Answer**:
- A protein has **two terminal amino acids** and they are called **N-terminal and C-terminal**.