Amino terminal and carboxyl terminal are observed in

Options

A. primary structure of the protein
B. Secondary structure of DNA
C. sugar molecule
D. primary structure of RNA

Answer

To solve the question regarding the observation of amino terminal and carboxyl terminal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Amino Terminal (N-terminus)**: This is the end of a protein or polypeptide that has a free amino group (-NH2). It is referred to as the N-terminus because it contains nitrogen.
- **Carboxyl Terminal (C-terminus)**: This is the end of a protein or polypeptide that has a free carboxyl group (-COOH). It is referred to as the C-terminus because it contains carbon.

2. **Identifying Where These Terms Are Found**:
- Amino and carboxyl terminals are specific to proteins. They denote the start and end of a polypeptide chain, respectively.

3. **Analyzing the Options**:
- **Option A: Primary Structure of the Protein**: The primary structure of a protein is defined as the linear sequence of amino acids linked by peptide bonds. This structure indeed has an amino terminal at one end and a carboxyl terminal at the other.
- **Option B: Secondary Structure of DNA**: This option is irrelevant as DNA does not have amino or carboxyl terminals.
- **Option C: Sugar Molecule**: Sugars do not have amino or carboxyl terminals; they are carbohydrates.
- **Option D: Primary Structure of RNA**: While RNA does have a sequence of nucleotides, it does not have amino or carboxyl terminals as it is not a protein.

4. **Conclusion**:
- The only option that correctly identifies where amino terminal and carboxyl terminal are observed is **Option A: Primary Structure of the Protein**.

### Final Answer:
The correct answer is **Option A: Primary Structure of the Protein**.