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Proteins and Nucleic Acids

Proteins and Nucleic Acids. AP Biology. Proteins. From Greek word “preteios” meaning “first place”. More than 50% of dry weight in most cells. Most structurally and functionally diverse group of biomolecules Functions: Enzymes – pepsin, polymerase, helicase Structure – keratin, collagen

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Proteins and Nucleic Acids

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  1. Proteins and Nucleic Acids AP Biology

  2. Proteins • From Greek word “preteios” meaning “first place”. • More than 50% of dry weight in most cells. • Most structurally and functionally diverse group of biomolecules • Functions: • Enzymes – pepsin, polymerase, helicase • Structure – keratin, collagen • Carriers and transport – membrane channels • Receptors and binding - antibodies • Contraction – Actin and myosin • Signaling - insulin • Storage – bean seed proteins

  3. Protein Structure • Monomer = amino acid • 20 different amino acids • Polymer = polypeptide • Protein can be one or more polypeptide chains folded and bonded together • Large and complex molecules • Complex 3-D shape Hemoglobin Rubisco

  4. Proteins • There are 10’s to 1000’s of proteins in each of us. Each has a different structure and function. • Insulin • Structure determined in late 1940’s to early 1950’s by Frederick Sanger.

  5. Amino Acids • Structure • Central carbon • Amino group • Carboxyl group (acid) • R group (Side chain) • Variable group • Confers unique chemical properties of the amino acid • Different in each of the 20 amino acids

  6. Building Proteins • Peptide bonds form by condensation synthesis reaction. • Link carboxyl group of 1 amino acid to the amino group of another amino acid.

  7. Building Proteins • Polypeptide chains • N-terminus = NH2 end • C-terminus = COOH end • Repeated sequence (N-C-C) is the polypeptide backbone. • Can only grow in one direction.

  8. Primary Structure • Order of amino acids in chain • Amino acid sequence is determined by gene (DNA) • Slight change in amino acid sequence can affect protein’s structure and it’s function

  9. Sickle Cell Anemia

  10. Secondary Structure • Segments of the polypeptide chain are coiled or folded in certain patterns • These are due to hydrogen bonds at regular intervals along the backbone

  11. Tertiary Structure • “whole molecule folding” • Irregular contortions due to the bonding between side chains of various amino acids

  12. Quaternary Structure • More than one polypeptide chain joined together • This is when a protein is functional!!!

  13. Review of the Levels of Protein Structure

  14. Denature a Protein • Unfolding a protein • Disrupt tertiary structure • Causes • pH • Salt concentration • Temperature • Disrupts hydrogen bonds, ionic bonds and disulfide bridges • Destroys functionality • Some proteins can return to their functional shape. Many can not!!!! 

  15. Denaturation

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