Protein structure and function

The following session will cover protein structure and function within the context of this subject, focusing on how structural hierarchy underpins protein roles in catalysis, signalling, transport, and disease. Proteins have a hierarchical organization. The primary structure is the linear amino acid sequence joined by peptide bonds, encoding information for higher levels. Secondary structure refers to patterns like alpha helices and beta sheets stabilized by hydrogen bonds. Tertiary structure is the three-dimensional folding of a single polypeptide, maintained by hydrophobic effects, ionic interactions, disulfide bridges, and van der Waals forces. Many proteins also form quaternary structures— multi-subunit complexes stabilized by similar forces. Together, these levels define the functional form of a protein. Protein structure is stabilized by a range of interactions. Hydrogen bonds within the backbone and between side chains maintain secondary and tertiary structures. Electrostatic interactions, like salt bridges, support stability. Hydrophobic effects are crucial—nonpolar side chains cluster inside, away from water, driving folding. Disulfide bonds between cysteine residues add rigidity, especially in extracellular proteins. These forces are precisely coordinated; even minor disruptions can destabilize proteins or alter function emphasizing the sensitive link