Chapter 3 Lecture Outline

Chapter 3 Lecture Outline - Biology 100 Vandan Desai...

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Biology 100 Vandan Desai P a g e | 1 Chapter 3: Protein Structure and Function (Lecture Outline) -------------------------------------------------------------------------------------------------------------------------- I. Amino Acids A. Proteins are composed of 20 different building blocks called amino acids B. Structure of Amino Acids: i. Carbon atoms participate in 4 bonds b/c they have 4 unpaired valence electrons ii. First bond – attaches carbon to NH2 ( amino functional group ) iii. Second bond – links carbon to COOH ( carboxyl functional group ) Acidic b/c its two oxygen atoms are highly electronegative They pull electrons away from hydrogen atom – relatively easy for this group to lose a proton iv. Third bond – links carbon to a hydrogen atom v. Fourth bond – R-group or side chain ( makes each amino acid unique ) C. In water at pH 7, the concentration of protons causes the amino group to act as a base . It attracts a proton to form NH 3 + . The carboxyl group , in contrast, loses a proton to form COO - . This helps amino acids stay in solution and add to their chemical reactivity. D. &ature of Side Chains: i. Hydrophobic (“water-fearing”) R-groups: Amino acids with nonpolar side chains do not have charged or electronegative atoms capable of forming hydrogen bonds with water Tend to coalesce in aqueous solution ii. Hydrophilic (“water-loving”) R-groups: Amino acids w/ polar or charged side chains interact readily with water Dissolve in water easily iii. Variation in the behavior of amino acids results from variation in the structure of their R-groups E. Isomers: (molecules that have different structures but the same molecular formula) i. Structural isomers: have the same atoms but differ in the order in which covalently bonded atoms are attached
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This note was uploaded on 03/08/2010 for the course BIOL 100 taught by Professor Staff during the Fall '07 term at UMBC.

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Chapter 3 Lecture Outline - Biology 100 Vandan Desai...

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