chap3 - Nucleic Acids, Proteins, and Enzymes PROTEINS 2...

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Unformatted text preview: Nucleic Acids, Proteins, and Enzymes PROTEINS 2 Proteins Diversity in Structure and Function Proteins are the most diverse biological molecule (structural, nutritious, enzyme, transport, communication, and defense proteins) Cells build thousands of different proteins by stringing together amino acids in different orders 3 PROTEINS FUNCTIONS ENERGY STORAGE ENZYMES -POISONS STRUCTURAL-TRANSPORT MOVEMENT-HORMONES ANTIBODIES 4 Enzymes catalytic proteins Defensive proteins (e.g., antibodies) Hormonal and regulatory proteins control physiological processes Receptor proteins receive and respond to molecular signals Storage proteins store amino acids Major functions of proteins: Structural proteins physical stability and movement Transport proteins carry substances (e.g., hemoglobin) Genetic regulatory proteins regulate when, how, and to what extent a gene is expressed Protein monomers are amino acids . Amino and carboxylic acid functional groups allow them to act as both acid and base. The R group differs in each amino acid. C O C H CH 2 C H H 2 N C O OH OH CH 2 glutamic acid (glu) C O C H H 2 N CH 2 C H OH CH 2 CH 2 NH C NH NH 2 arginine (arg) C O C H H 2 N CH 2 C H OH C O C H H 2 N CH 2 C H OH hydrophilic CH CH 3 hydrophobic leucine (leu) phenylalanine (phe) C O C H 2 N C H OH cysteine (cys) forms disulfide bridges CH 2 SH CH 3 8 Only 20 amino acids occur extensively in the proteins of all organisms. They are grouped according to properties conferred by the R groups. Amino Acid All 20 amino acids are fundamentally the same in structure Central Carbon covalently bonded to an amino group, carboxylic acid group, hydrogen, and a variable group - its this group that establishes the chemical nature of the amino acid 10 The Twenty Amino Acids in Proteins (Part 1) The Twenty Amino Acids in Proteins (Part 2) The Twenty Amino Acids in Proteins (Part 3) The Twenty Amino Acids in Proteins (Part 4) AMINO ACIDS LINKED THROUGH A COVALENT BOND WHICH IS CALLED A PEPTIDE Polypeptides Protein synthesis involves the formation of amino acid chains called polypeptides Polypeptide A chain of amino acids bonded together by peptide bonds in a condensation reaction between the amine group of one amino acid and the carboxyl group of another amino acid 16 Formation of a Peptide Linkage Fig. 3-16a, p. 44 A Order of amino acids in a new polypeptide chain. Methionine (met) is the first amino acid in this example. B In a condensation reaction, a peptide bond forms between the methionine and the next amino acid, alanine (ala) in this example. Leucine (leu) will be next....
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chap3 - Nucleic Acids, Proteins, and Enzymes PROTEINS 2...

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