Question

Differentiate between primary, secondary, tertiary, and quaternary structures of proteins.

Answer 1

Proteins have four levels of structure essential to function: primary (amino acid sequence), secondary (local folding into α-helices or β-pleated sheets), tertiary (three-dimensional folding of the entire peptide chain), and quaternary (arrangement of multiple subunits).

Step-by-step explanation:

Differences Between Protein Structure Levels

The structure of protein is essential for its function and is organized into four distinct levels: primary, secondary, tertiary, and quaternary. The primary structure of a protein consists of its unique sequence of amino acids. As for the secondary structure, it is characterized by local folding into patterns such as α-helices and β-pleated sheets. The tertiary structure represents the further three-dimensional folding of the entire peptide chain, resulting in a complex globular shape. When a protein consists of more than one polypeptide chain, they associate to form the quaternary structure, which is the arrangement of these multiple subunits.

Each level of protein structure is critical to the protein's ultimate function. Disruption of these structures, such as through denaturation, can result in loss of function. The structure is maintained by various interactions including hydrogen bonding, ionic bonds, disulfide linkages, and dispersion forces.

Answer 2

Biologists describe the structure of protein at four levels: Primary, secondary, tertiary and quaternary.

Step-by-step explanation:

1. Primary structure: It is the sequence of amino acids in the polypeptide chain. It only gives us the positional information of amino acids within a protein like which one is first, which one is second and so on. We can see only peptide bonds in primary structure.

Also the first amino acid is known as N-terminal and the last as C-terminal.

2. Secondary structure: The protein thread folds either in the form of helix or beta pleated sheet to form the secondary structure.

In alpha helix, there is hydrogen bonding between every fourth amino acid. Example keratin protein of hair.

In beta pleated sheets, two or more polypeptide strands are held together by intermolecular hydrogen bonding.

3. Tertiary structure: The long polypeptide chain usually folds upon itself like a hollow wollen ball. This is termed as tertiary structure. Involves several linkages like hydrogen bond, hydrophobic bond, ionic bond, covalent bond, van der walls forces. Active sites are formed and protein gains functionality. Example: myoglobin

4. Quaternary structure: Quaternary structure is formed when there are more than one polypeptide chains. For example: hemoglobin has four helical polypeptide chains.