Which of the following statements about the structure of proteins is true

Options

A. The sequence of amino acids in a protein represents the secondary structure
B. Helices of proteins are always left handed
C. Adult human haemoglobin consists of two subunits
D. Protein are heteropolymers containing strings of amino acids.

Answer

To determine which statement about the structure of proteins is true, let's analyze each option step by step:

### Step-by-Step Solution:

1. **Understanding Protein Structure**:
- Proteins are made up of amino acids, and their structure can be categorized into four levels: primary, secondary, tertiary, and quaternary.

2. **Evaluating Statement 1**:
- The first statement claims that the sequence of amino acids in a protein represents the secondary structure.
- **Analysis**: This is incorrect. The sequence of amino acids is known as the primary structure, not the secondary structure. The secondary structure refers to local folded structures that form within a protein due to hydrogen bonding, such as alpha helices and beta sheets.

3. **Evaluating Statement 2**:
- The second statement suggests that helices of proteins are always left-handed.
- **Analysis**: This is also incorrect. Most protein helices, such as the alpha helix, are right-handed. Therefore, this statement is false.

4. **Evaluating Statement 3**:
- The third statement states that adult hemoglobin consists of two subunits.
- **Analysis**: This statement is incorrect. Adult hemoglobin actually consists of four polypeptide chains (two alpha and two beta chains), making it a tetramer, not a dimer.

5. **Evaluating Statement 4**:
- The fourth statement claims that proteins are heteropolymers containing strings of amino acids.
- **Analysis**: This statement is true. Proteins are indeed heteropolymers made up of various amino acids linked together by peptide bonds. There are 20 different amino acids that can combine in numerous ways to form different proteins.

6. **Conclusion**:
- Based on the analysis, the only true statement about the structure of proteins is the fourth one: "Proteins are heteropolymers containing strings of amino acids."

### Final Answer:
The correct statement about the structure of proteins is: **"Proteins are heteropolymers containing strings of amino acids."**

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