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© www.chemsheets.co.uk A2 1103 22-July-2016 AMINO ACIDS H H2N amine group C COOH R © www.chemsheets.co.uk carboxylic acid group A2 1103 22-July-2016 AMINO ACIDS From Dept Bio Pemn State Joining amino acids together to make polypeptides and proteins: H H2N C H + COOH H2N R COOH R - H2O H2N C H O C C R Condensation reaction: molecules join and water is eliminated H N C H R COOH © www.chemsheets.co.uk A2 1103 22-July-2016 Public domain image from wikipedia Breaking down polypeptides and proteins into amino acids: H2N H O C C H R Needs: acid or enzyme N C H R Hydrolysis reaction: reaction with water in which O-H bond breaks + H2O H H2N C R COOH H COOH + H2N C COOH R © www.chemsheets.co.uk A2 1103 22-July-2016 Amino acids be analysed by TLC (can be stained using ninhydrin) or view results under UV light solvent front Rf values can identify amino acids 5 cm 4 cm For substance R Rf = 3 = 0.6 5 For substance S Rf = 4 = 0.8 5 3 cm starting line R S © www.chemsheets.co.uk A2 1095 17-Jul-16 PROTEINS Public domain image from wikipedia Public domain image from wikipedia Helix held in shape by hydrogen bonds α-helix β-sheet α-helix β-sheet Public domain image from wikipedia 1y structure held by: covalent bonds between amino acids 2y structure held by: hydrogen bonds 3y structure held by: hydrogen bonds disulfide bonds ionic attractions (e.g. COO– and NH3+) etc Public domain image from wikipedia DNA DNA This is a NUCELOTIDE phosphate group P BASE 2-deoxyribose SUGAR one of 4 bases: • adenine • guanine • cytosine • thymine DNA P BASE DNA is a polymer made of: -sugar-phosphate-sugar-phosphate- SUGAR P BASE SUGAR P BASE SUGAR DNA part of a chain 2-deoxyribose - phosphate - DNA adenine bonding site to deoxyribose H bonding site to base partner DNA thymine bonding site to deoxyribose H bonding site to base partner DNA guanine bonding site to deoxyribose H bonding site to base partner DNA cytosine bonding site to deoxyribose H bonding site to base partner - DNA BASE PAIRS IN DNA hydrogen bonding between base pairs holds DNA strands together thymine cytosine 0 0 0 0 guanine adenine BASE PAIRS IN DNA Public domain image from wikipedia Public domain image from wikipedia CIS-PLATIN Very effective drug to fight cancer (e.g. testicular) Pt binds to N in guanine in DNA (substitutes for Cl- ligands) Stops DNA replication as binds two chains together Cl Cl Pt NH3 NH3 ENZYMES • are proteins that act as catalysts in biological systems • they bind to a substrate but are very stereospecific Public domain image from wikipedia ENZYMES • Drug action – blocks active sites to inhibit enzymes Public domain image from wikipedia
