Biomolecules

Protein structures are classified based on recurring structural motifs, which are common arrangements of secondary structures like α-helices and β-sheets. Motifs are crucial for determining protein function and interactions.

Phosphatidylcholine and phosphatidylserine are glycerophospholipids, consisting of a glycerol backbone, two fatty acid chains, and a phosphate group with a head group (e.g., choline or serine).

- β-galactosidase (A - II): Its molecular weight is approximately 116.25 kDa.
- Bovine Serum Albumin (B - III): This protein has a molecular weight of 66.2 kDa.
- Ovalbumin (C - IV): Its molecular weight is 14.4 kDa.
- Lysozyme (D - I): The molecular weight is 45 kDa.

Frederick Sanger sequenced insulin, the first protein to have its amino acid sequence determined. This achievement was pivotal in the study of proteins and molecular biology.

The quaternary structure of a protein describes the arrangement and interactions of multiple polypeptide chains (subunits) within a single protein complex. Examples include hemoglobin and collagen.

- (A) Correct: Wool proteins, when heated, shift from their native β-sheet structure to an α-helical conformation, causing the material to shrink.
- (B) Incorrect: While silk β-sheets are stable, this does not explain the behavior of wool.
- (C) Incorrect: Wool’s polypeptide chains do not remain in their β-sheet conformation upon heating.
- (D) Incorrect: Silk β-sheets are more stable than wool’s α-helix, but this does not directly address the question.

- (A) Correct: Lipids such as phosphatidylinositol derivatives act as cofactors or signaling molecules.
- (B) Correct: Prostaglandins are synthesized from arachidonic acid, a polyunsaturated fatty acid.
- (C) Correct: Steroid hormones like cortisol and testosterone are derived from cholesterol (asterol).
- (D) Correct: Vitamins D, A, E, and K are fat-soluble and stored in body fat.