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Proteins

Proteins. Proteins. Most structurally and functionally diverse group: Structural material Enzymes Transport molecules Cell communication Defense movement General structure of an amino acid (building block). Proteins.

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Proteins

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  1. Proteins

  2. Proteins • Most structurally and functionally diverse group: • Structural material • Enzymes • Transport molecules • Cell communication • Defense • movement • General structure of an amino acid (building block)

  3. Proteins There are 20 different R-groups in living organisms and therefore 20 different amino acids See page 42-43 for the various R group structures

  4. Proteins Amino acids join together to form polypeptides through condensation reactions The bond is called a peptide bond:

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

  6. Proteins • Of 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 product • There are 4 structural levels in the creation of a protein

  7. Proteins • Primary (1º) Structure • The order of amino acids in a chain • The sequence of amino acids is determined by the genes that “coded” for it • Structure determines function! • Consider sickle cell anemia

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

  9. Proteins • Secondary (2º) structure • The H-bonds among the amino acids form alpha-helices or beta-pleated sheets

  10. Proteins • Tertiary (3°) Structure • Interactions between distant amino acids create “whole molecule” folding • Hydrophobic Interactions: cytoplasm is water-based, so hydrophobic amino acids cluster away from water • H-bonds and ionic bonds may form • Disulfide bridges form between sulfur groups. These interactions anchor the 3D shape of the protein

  11. Proteins

  12. Proteins • Quaternary (4°) structure: • Clustering of two or more tertiary polypeptides through hydrophobic interactions • Polypeptides then become a functional protein

  13. Proteins • Protein denaturation: the unfolding and destruction of protein functionality • Causes: pH, salinity, temperature • These can disrupt disulfide bonds, H-bonds, and ionic bonds • The 3D shape is altered • Some proteins can return to their functional shape after, but some cannot

  14. Proteins • Try these: • P.50 #19, 20, 22, 23, 24, 25,

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