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Proteins and Nucleic Acids

Proteins, derived from the Greek word "preteios," are crucial biomolecules constituting over 50% of cell weight. They serve as enzymes, carriers, receptors, and more, with diverse functions like structure, signaling, and storage. Comprising amino acids, they exhibit complex 3-D structures determining functionality, such as in hemoglobin and insulin. The protein structure hierarchy includes primary, secondary, tertiary, and quaternary levels, vulnerable to denaturation. Understand the significance and intricacies of proteins in biology.

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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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