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ProteinsProteinsMost structurally and functionally diverse group:

Structural materialEnzymesTransport moleculesCell communicationDefensemovement

General structure of an amino acid (building block)

ProteinsThere are 20 different R-groups in living organisms and therefore 20 different amino acidsSee page 42-43 for the various R group structures

ProteinsAmino acids join together to form polypeptides through condensation reactionsThe bond is called a peptide bond:

Polypeptides can only be built in one directionThey have an N-terminus (NH2) and a C-terminus (COOH)A series of amino acids is called a polypeptide chain

ProteinsOf the 20 amino acids, 8 are considered to be essential because humans cannot produce them; they must be consumed

The word protein suggests that a polypeptide chain has gone through several degrees of structural changes to become a final productThere are 4 structural levels in the creation of a proteinProteinsPrimary (1) StructureThe order of amino acids in a chainThe sequence of amino acids is determined by the genes that coded for itStructure determines function!Consider sickle cell anemia

Sickle cell anemia results from one single amino acid substitution at the 6 position (6th AA)

ProteinsSecondary (2) structureThe H-bonds among the amino acids form alpha-helices or beta-pleated sheets

ProteinsTertiary (3) Structure Interactions between distant amino acids create whole molecule foldingHydrophobic Interactions: cytoplasm is water-based, so hydrophobic amino acids cluster away from waterH-bonds and ionic bonds may formDisulfide bridges form between sulfur groups. These interactions anchor the 3D shape of the proteinProteins

ProteinsQuaternary (4) structure:Clustering of two or more tertiary polypeptides through hydrophobic interactionsPolypeptides then become a functional protein

ProteinsProtein denaturation: the unfolding and destruction of protein functionalityCauses: pH, salinity, temperatureThese can disrupt disulfide bonds, H-bonds, and ionic bondsThe 3D shape is alteredSome proteins can return to their functional shape after, but some cannot

ProteinsTry these:P.50 #19, 20, 22, 23, 24, 25,