BIOL 200 Lecture Notes - Lecture 19: W. H. Freeman And Company, Alpha Helix, Protein Folding
13 Nov 2016
School
Department
Course
Professor
Document Summary
Peptides are short string of up to 20-30 amino acids (a. a. ) Proteins: a polypeptide or a complex of polypeptides with well-defined. Functions of proteins are determined by its overall shape that is driven by a. a. sequence and distribution of a. a. side chain with their chemical properties. Two major class of a. a side chains: hydrophilic -> polar charge distribution, hydrophobic -> non-polar charge distribution. Water molecules surround the hydrophobic residues like a cage -> low entropy. Hydrophobic residues coalesce which allows some water molecules to free and reduce their constraint, making a one big cage -> high entropy. Secondary: local folding: alpha helix and beta sheet. Quaternary: assembly of molecules with definite structural complex. Also tends to have periodicity of hydrophobic residues. Beta pleated sheets: also have hydrophobic periodicity at every 2 residues. Lodish et al 8th ed fig 3-5, 3-6. ~100-150 a. a. long region, compactly folded, can be made of various motifs.
