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Proteins

Proteins. Genetic information in DNA codes specifically for the production of proteins Cells have thousands of different proteins, each with a specific job. 1. An overview of protein functions. Table 5.1. 2. Enzymes

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Proteins

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  1. Proteins Genetic information in DNA codes specifically for the production of proteins Cells have thousands of different proteins, each with a specific job 1

  2. An overview of protein functions Table 5.1 2

  3. Enzymes Are a type of protein that acts as a catalyst, speeding up chemical reactions Substrate binds to enzyme. 1 Active site is available for a molecule of substrate, the reactant on which the enzyme acts. 2 2 Substrate (sucrose) Glucose Enzyme (sucrase) OH H2O Fructose H O 4 Products are released. 3 Substrate is converted to products. Figure 5.16 3

  4. Polypeptides Polypeptides Are polymers (chains) of amino acids A protein Consists of one or more polypeptides 4

  5. Proteins are made of monomers called amino acids Amino acids contain both carboxyl and amino groups Differ in their properties due to differing side chains, called R groups 5

  6. Twenty Amino Acids 20 different amino acids make up proteins CH3 CH3 CH3 CH CH2 CH3 CH3 H CH3 H3C CH3 CH2 CH O O O O O H3N+ H3N+ H3N+ H3N+ C H3N+ C C C C C C C C C O– O– O– O– O– H H H H H Valine (Val) Leucine (Leu) Isoleucine (Ile) Glycine (Gly) Alanine (Ala) Nonpolar CH3 CH2 S H2C CH2 O NH CH2 H2N C C CH2 CH2 O– CH2 O O O H H3N+ H3N+ C C C C H3N+ C C O– O– O– H H H Phenylalanine (Phe) Proline (Pro) Methionine (Met) Tryptophan (Trp) Figure 5.17 6

  7. OH NH2 O C NH2 O C OH SH CH2 CH3 OH Polar CH2 CH CH2 CH2 CH2 CH2 O O O O O O H3N+ H3N+ H3N+ H3N+ H3N+ H3N+ C C C C C C C C C C C C O– O– O– O– O– O– H H H H H H Glutamine (Gln) Tyrosine (Tyr) Asparagine (Asn) Cysteine (Cys) Serine (Ser) Threonine (Thr) Basic Acidic NH3+ NH2 NH+ O– O –O O CH2 C NH2+ C C NH Electrically charged CH2 CH2 CH2 CH2 CH2 O O H3N+ H3N+ CH2 CH2 C CH2 C C C O O– H3N+ O– CH2 C CH2 C H O H H3N+ O– C C CH2 H O O– H3N+ C C H O– H Lysine (Lys) Histidine (His) Arginine (Arg) Glutamic acid (Glu) Aspartic acid (Asp) http://www.youtube.com/watch?v=QHvklS77_U0 7

  8. Amino Acid Polymers Amino acids Are linked by peptide bonds http://www.youtube.com/watch?feature=endscreen&v=WKBAuKsTkZs&NR=1 Amino Terminus (end) CarboxylTerminus (end) 8

  9. Protein Conformation and Function A protein’s specific conformation(shape) determines how it functions 9

  10. Four Levels of Protein Structure Primary structure Is the unique sequence of amino acids in a polypeptide The order of amino acids is determined by inherited genetic information Amino acid subunits +H3NAmino end Pro Thr Gly Gly Thr Gly Glu Seu Lys Cys Pro Leu Met Val Lys Val Leu Asp Ala Arg Val Gly Ser Pro Ala Glu Lle Asp Thr Lys Ser Tyr Trp Lys Ala Leu Gly lle Ser Pro Phe His Glu His Ala Glu Val Thr Phe Val Ala Asn lle Thr Asp Ala Tyr Arg Ser Ala Arg Pro Gly Leu Leu Ser Pro Tyr Ser Tyr Ser Thr Thr Ala o Val c Val Glu – Lys o Thr Pro Asn Carboxyl end Figure 5.20 10

  11. Sickle Cell Disease http://www.youtube.com/watch?v=yobHMYhHAXE

  12. Secondary structure Is the folding or coiling of the polypeptide Results from interactions between amino acids (NOT THE R-GROUPS) Includes the  helix and the  pleated sheet held together by hydrogen bonds H H Figure 5.20 12

  13. H H H H H H O O O O O O O H H H H H H R R R R R R R C C C C C C C C C C C C C N N N N N N N N N N N N N C C C C C C C C C C C C C C R R R R R R H H H H H H H O O O O O O O H H H H H H H  pleated sheet H O H H Amino acidsubunits C C N N N C C C R H O H H H H H H N N N N N N  helix C C O C H H H C C C R R R R R H H C C C C C C O O O O H C R O C C O H C O N N H C C R R •  helix – bonds between every 4th amino acid •  pleated sheet – when 2 or more regions of the chain line up parallel

  14. Tertiary structure Is the overall three-dimensional shape of a polypeptide Results from interactions between R groups Hydrophobic interactions and van der Waalsinteractions CH CH2 CH2 H3C CH3 OH Polypeptidebackbone H3C CH3 Hyrdogenbond CH O HO C CH2 CH2 S S CH2 Disulfide bridge O -O C CH2 CH2 NH3+ Ionic bond 14

  15. Quaternary structure Is the overall protein structure that results when two or more polypeptides subunits come together Polypeptidechain Collagen  Chains Iron Heme  Chains Hemoglobin 15

  16. Review of Protein Structure +H3N Amino end Amino acid subunits helix http://www.youtube.com/watch?v=uqfflg5zjC0 16

  17. A protein’s shape (conformation) also depends on the physical and chemical conditions of the protein’s environment E.g. Temperature, pH, etc. affect protein structure 17

  18. Denaturation occurs when a protein unravels and loses its native conformation (shape), rendering it unable to carry out its biological functions Denaturation Normal protein Denatured protein Renaturation Figure 5.22 18

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