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lecture 4 biao ding

lecture 4 biao ding - Biol 113 AU2010 Lecture 4...

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1 Biol 113 AU2010 Lecture 4 Macromolecules (II) A. Proteins B. Nucleic acids A. Proteins Proteins account for more than 50% of the dry mass of most cells Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances Table 5.1 Polypeptides Polypeptides are polymers built from the same set of 20 amino acids A protein consists of one or more polypeptides Amino acids are organic molecules with carboxyl and amino groups Amino acids differ in their properties due to differing side chains, called R groups Amino group Carboxyl group α carbon Fig. 5.17a Nonpolar Glycine (Gly or G) Alanine (Ala or A) Valine (Val or V) Leucine (Leu or L) Isoleucine (Ile or I) Methionine (Met or M) Phenylalanine (Phe or F) Tryptophan (Trp or W) Proline (Pro or P) Polar Asparagine (Asn or N) Glutamine (Gln or Q) Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Fig. 5.17b
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2 Acidic Arginine (Arg or R) Histidine (His or H) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Basic Electrically charged Fig. 5.17c Amino Acid Polymers Amino acids are linked by peptide bonds A polypeptide is a polymer of amino acids Polypeptides range in length from a few to more than a thousand monomers Each polypeptide has a unique linear sequence of amino acids Peptide bond Amino end (N-terminus) Peptide bond Side chains Backbone Carboxyl end (C-terminus) (a) (b) Fig. 5.18 Protein Structure and Function A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape A ribbon model of lysozyme (a)
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