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Proteins

Proteins. Multipurpose molecules. Proteins. Most structurally & functionally diverse group Some Functions of Proteins: enzymes (pepsin, DNA polymerase) Biological structures (keratin, collagen) carriers & transport (hemoglobin, aquaporin) cell communication

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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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