Quaternary structure of protein:

Options

A. Consists of four subunits
B. May be either `alfa` or `beta`-helix
C. ls unrelated to the function of protein
D. Is dictated by the primary stricture of the subunits

Answer

### Step-by-Step Solution for the Quaternary Structure of Protein

1. **Understanding Protein Structure Levels**:
- Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
- The primary structure is the sequence of amino acids in a polypeptide chain.

**Hint**: Remember the hierarchy of protein structure: primary → secondary → tertiary → quaternary.

2. **Identifying the Secondary Structure**:
- The secondary structure of proteins can take the form of alpha helices and beta sheets.
- These structures are stabilized by hydrogen bonds between the backbone atoms in the polypeptide chain.

**Hint**: Focus on the types of secondary structures and their stabilizing interactions.

3. **Defining Tertiary Structure**:
- The tertiary structure is the three-dimensional shape of a single polypeptide chain, formed by the folding of the secondary structures.
- This folding is influenced by various interactions, including hydrogen bonds, ionic bonds, and hydrophobic interactions.

**Hint**: Tertiary structure is about the overall 3D conformation of a single polypeptide.

4. **Explaining Quaternary Structure**:
- The quaternary structure refers to the assembly of multiple polypeptide chains (subunits) into a single functional protein complex.
- These subunits can be identical or different and are held together by various types of bonds, including hydrogen bonds and covalent bonds.

**Hint**: Quaternary structure involves multiple polypeptide chains coming together.

5. **Evaluating the Statements**:
- **Statement 1**: "The quaternary structure of protein has four subunits."
- This is incorrect as quaternary structures can have more or less than four subunits.
- **Statement 2**: "Is it in the form of alpha and beta helix?"
- This is incorrect because alpha and beta structures are part of the secondary structure, not the quaternary.
- **Statement 3**: "Is unrelated to function of protein?"
- This is incorrect; the quaternary structure is often crucial for the protein's function.
- **Statement 4**: "Is dictated by primary structure of protein?"
- This is correct; the primary structure determines how the protein folds and assembles into its quaternary structure.

**Hint**: Analyze each statement critically to determine its accuracy based on your understanding of protein structure.

6. **Conclusion**:
- The correct statement regarding the quaternary structure of proteins is that it is dictated by the primary structure of the protein. This means that the sequence of amino acids (primary structure) ultimately influences how the protein folds and assembles into its quaternary form.

**Hint**: Always connect the different levels of protein structure to understand how they influence each other.