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Proteins

Learn about the diverse functions & complex structure of proteins, including amino acids, peptide bonds, protein denaturation, and levels of protein organization. Discover how primary, secondary, tertiary, and quaternary structures affect protein function. Dive into nucleic acids as the blueprint for building proteins and storing genetic information.

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Proteins

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  1. Proteins Multipurposemolecules

  2. Proteins • Most structurally & functionally diverse group • Some Functions of Proteins: • enzymes (pepsin, DNA polymerase) • Biological structures (keratin, collagen) • carriers & transport (hemoglobin, aquaporin) • cell communication • signals(insulin & other hormones) • receptors • defense (antibodies) • movement (actin & myosin) • storage (bean seed proteins)

  3. Protein Structure • Monomer( 1 unit) =amino acids • 20 different amino acids • polymer =polypeptide • protein can be one or more polypeptide chains folded & bonded together • large & complex molecules • complex 3-D shape hemoglobin growthhormones Rubisco

  4. H O | —C— | H || C—OH —N— H Amino acids • Structure • central carbon • amino group (typically ionized) • carboxyl group (an acid which is also ionized) • R group (side chain) • variable group • different variable group makes a different amino acid • confers unique chemical properties to each amino acid Recall: Structure determines function R

  5. Amino acids have both acidic (carboxyl) and basic (amino) properties. When dissolved in water, the carboxyl group donates a H+ ion to the amino group to possess an extra hydrogen and therefore a net +ve charge. Amino Acids cont’d

  6. R groups • Amino acids may be polar, non-polar, or charged (acidic or basic). • This depends on the nature of the side chains. • Generally, acidic aa’s possess a carboxyl group on the side chain and basic aa’s contain an amino group on the side chain.

  7. Effect of different R groups: Nonpolar amino acids • nonpolar & hydrophobic Why are these nonpolar & hydrophobic?

  8. Effect of different R groups: Polar amino acids • polar or charged & hydrophilic Why are these polar & hydrophillic?

  9. H2O peptidebond Building proteins • Peptide bonds • Formed by a condensation reaction between NH2 (amine) of one amino acid & COOH (carboxyl) of another (amide bond) • C–N bond dehydration synthesis

  10. hemoglobin collagen Protein structure & function • Function depends on structure • 3-D structure • twisted, folded, coiled into unique shape pepsin

  11. Now…. LETS DISCUSS LEVELS OF PROTEIN ORGANIZATION Please review pg. 27 in your textbook tonight!

  12. Primary (1°) Structure • Order of amino acids in chain • amino acid sequence determined by gene (DNA) • slight change in amino acid sequence can affect protein’s structure & its function • even just one amino acid change can make all the difference!

  13. Sickle Cell Anemia

  14. Secondary (2°) structure • “Local folding” • folding along short sections of polypeptide • interactions between adjacent amino acids • H bonds • weak bonds between R groups • forms sections of 3-D structure • -helix • -pleated sheet

  15. Secondary (2°) structure

  16. Tertiary (3°) structure • “Whole molecule folding” • interactions between distant amino acids • hydrophobic interactions • cytoplasm is water-based • nonpolar amino acids cluster away from water • H bonds & ionic bonds • disulfide bridges • covalent bonds between sulfurs in sulfhydryls (S–H) • anchors 3-D shape

  17. Quaternary (4°) structure • More than one polypeptide chain bonded together • only then does polypeptide become functional protein • hydrophobic interactions hemoglobin collagen = skin & tendons

  18. Protein structure (review) R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3° multiple polypeptides hydrophobic interactions 1° amino acid sequence peptide bonds 4° 2° determinedby DNA R groups H bonds

  19. Protein denaturation • Unfolding a protein • conditions that disrupt intermolecuar bonds • temperature • pH • Exposure to chemicals • destroys functionality • some proteins can return to their functional shape after denaturation, many cannot

  20. Nucleic Acids Informationstorage

  21. proteins DNA Nucleic Acids • Function: • genetic material • stores information • genes • blueprint for building proteins • DNA  RNA  proteins • transfers information • blueprint for new cells (mitosis) • blueprint for next generation (meiosis)

  22. Nucleic Acids • Examples: • RNA (ribonucleic acid) • single helix • DNA (deoxyribonucleic acid) • double helix • Structure: • monomers = nucleotides DNA RNA

  23. Nucleotides • 3 parts • nitrogen base (C-N ring) • pentose sugar (5C) • ribose in RNA • deoxyribose in DNA • phosphate(PO4)group • enzymes facilitate the formation of covalent bonds between the phosphate group of one nucleotide and the hydroxyl group on C3 of the adjacent nucleotide (see right). This is called a phosphodiester bond.

  24. Types of nucleotides • 2 types of nucleotides • different nitrogen bases • purines • double ring N base • adenine (A) • guanine (G) • pyrimidines • single ring N base • cytosine (C) • thymine (T) • uracil (U)

  25. Nucleic polymer • Backbone • sugar to PO4 bond • phosphodiester bond • new base added to sugar of previous base • Polymer (aka a strand) grows in one direction • N bases hang off the sugar-phosphate backbone

  26. Pairing of nucleotides • Nucleotides bond between DNA strands • H bonds • purine :: pyrimidine • A :: T • 2 H bonds • G :: C • 3 H bonds

  27. DNA molecule • Double helix • H bonds between bases join the 2 strands • A :: T • C :: G

  28. Macromolecule Review

  29. Carbohydrates • Structure / monomer • monosaccharide • Function • energy • raw materials • energy storage • structural compounds • Examples • glucose, starch, cellulose, glycogen glycosidic bond

  30. Lipids • Structure / building block • glycerol, fatty acid, cholesterol, H-C chains • Function • energy storage • membranes • hormones • Examples • fat, phospholipids, steroids ester bond (in a fat)

  31. Proteins • Structure / monomer • amino acids • levels of structure • Function • enzymes u defense • transport u structure • signals u receptors • Examples • digestive enzymes, membrane channels, insulin hormone, actin peptide bond

  32. Nucleic acids • Structure / monomer • nucleotide • Function • information storage & transfer • Examples • DNA, RNA phosphodiester bond

  33. RNA & DNA • RNA • single nucleotide chain • DNA • double nucleotide chain • N bases bond in pairs across chains • spiraled in a double helix

  34. Homework: • Learning Check • Pg. 28 #19-23 Fill in back of Macromolecule Handout ( Proteins & Nucleic Acids) Complete Functional Group Review handout

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