University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

402

Pages:

6
Author:

Sheha A.

Beta Sheet β-sheet is a secondary structure of proteins. It is formed by hydrogen bonds between the backbone amide groups of amino acids. β-sheets can be parallel or anti-parallel. Parallel β-sheet: The hydrogen bonds are formed between the backbones of amino acids that are oriented in the same direction. The hydrogen bonds are parallel to the direction of the peptide chain. Anti-parallel β-sheet: The hydrogen bonds are formed between the backbones of amino acids that are oriented in opposite directions. The hydrogen bonds are perpendicular to the direction of the peptide chains. Tertiary Structure Tertiary structure refers to the 3D folding of a polypeptide chain. It describes the arrangement of secondary structures like alpha helices and beta sheets. It is stabilized by various interactions: Disulfide bonds Hydrogen bonds Ionic bonds Hydrophobic interactions Hydrophobic Interactions: Hydrophobic side chains cluster together in the interior of the protein, away from water. This creates a hydrophobic core that stabilizes the protein's structure. Amino acids with hydrophobic side chains are often buried in the interior of the protein, while hydrophilic side chains are often exposed to the solvent. * Proteins contain strong covalent disulfide (S-S) bonds, which cross-link different parts of the protein chain. * Cysteine amino acids contain sulfhydryl groups (-SH) that can form disulfide bonds. * Disulfide bonds stabilize the tertiary structure of proteins. * Quaternary Structure * Proteins having more than one polypeptide chain show quaternary structure. * Quaternary structure refers to the spatial arrangement of an oligomeric protein. **Example:** * Hemoglobin, Immunoglobulins, Lactate dehydrogenase * Quaternary structure stabilizes the protein and creates new functions. * It involves various bonds: covalent bonds, ionic bonds, hydrogen bonds, hydrophobic interactions, and also van der Waals forces. * Interactions between polypeptide chains can be strong or weak. **Importance of Quaternary Structure:** * It creates new functions of proteins. * It stabilizes the protein structure. * It helps in the regulation of biological processes.