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Proteins Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known Monomer:

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Presentation on theme: "Proteins Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known Monomer:"— Presentation transcript:

1 Proteins Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known Monomer: amino acids (there are 20) ~ carboxyl (-COOH) group, amino group (NH 2 ), H atom, variable group (R)…. Variable group characteristics: polar (hydrophilic), nonpolar (hydrophobic), acid or base Three-dimensional shape (conformation) Polypeptides (dehydration reaction): peptide bonds~ covalent bond; carboxyl group to amino group (polar)

2 Amino acids

3 Primary Structure Conformation: Linear structure Molecular Biology: each type of protein has a unique primary structure of amino acids Ex: lysozyme Amino acid substitution: hemoglobin; sickle-cell anemia

4 Secondary Structure Conformation: coils & folds (hydrogen bonds) Alpha Helix: coiling; keratin Pleated Sheet: parallel; silk animation

5 –The presence of so many hydrogen bonds makes each silk fiber stronger than steel. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.21

6 Tertiary Structure Conformation: irregular contortions from R group bonding √hydrophobic √disulfide bridges √hydrogen bonds √ionic bonds

7 Quaternary Structure Conformation: 2 or more polypeptide chains aggregated into 1 macromolecule √collagen (connective tissue) √hemoglobin Protein structure video

8 Enzymes Catalytic proteins: change the rate of reactions w/o being consumed Free E of activation (activation E): the E required to break bonds

9 Enzymes are substrate specific Substrate- reactant that binds to enzyme Enzymes are catalysts Active site- pocket or groove that binds to substrate Must be specific fit; as bind the enzyme changes shape leading to even tighter fit= induced fit. animationanimation

10 Enzyme binding

11 Effects on Enzyme Activity Temperature pH Cofactors: inorganic, nonprotein helpers; ex.: zinc, iron, copper Coenzymes: organic helpers; ex.: vitamins

12 Enzyme Inhibitors Irreversible (covalent); reversible (weak bonds) Competitive: competes for active site (reversible); mimics the substrate Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics

13 Control of Metabolism Allosteric regulation- can either be inhibition or stimulation of activity..animanim

14 Con’t. Feedback inhibition- (common) –Metabolic pathway turned off by end product –animationanimation

15 Con’t. Cooperativity- active site stabilizes favorable conformational changes at all other subunits

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