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Lecture 9-08 - Lecture 9/08-Ch 4 NEED TO LEARN ALL 20 AMINO...

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Lecture 9/08-Ch 4 NEED TO LEARN ALL 20 AMINO ACIDS!!! Erythropoitin protein hormone (165 aa) glycoprotein produced in kidneys to stimulate bone marrow to make red blood cells increases amount of oxygen carried increases stamina for these patients cloned and manufactured in cultured cells--recombinant--billion dollar product for Amgen--also subject of a nasty patent fight that Amgen won used to treat anemia in chemo patients and dialysis patients (poor kidney function) second generation product now available that is partially modified with carbohydrate groups--supposed to be more active abused by athletes to increase perfomance by carrying more oxygen in blood due to more blood cells--can be very dangerous, blood becomes more viscous especially if dehydrated test determines recombinant vs. natural based on amount and type of carbohydrate present test is not as precise as other tests for steroids, etc. and may have a higher rate of false positive and subject to interpretation AMINO ACIDS R can be any of 20 different groups pK a of the COOH group is ~2-2.5 pK a of the NH 2 group is ~9-10 at pH 7 in cell carboxyl is in conjugate base form COO - amino is in conjugate acid form NH 3 + amphoteric-both acid and base character at pH 7 have equal + and - charges called zwitterions when electrically neutral R groups give each amino acid its unique properties (acidic, basic, hydrophobic, hydrophilic, aromatic, etc..) Amino Acid Structure the α- carbon is asymmetric, also called chiral carbon--see closer look 4A (p. 96) (glycene is exception to asymmetric structure) α- carbon has 4 different groups attached (except for glycine, whose R group is H) there are two possible arrangements in space stereoisomers-molecules that differ only in their arrangement in space D-isomers or L-isomers
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non-superimposable mirror images--enantiomers biological molecules exist either as D or L amino acids in proteins are in the L form Classes of amino acids aliphatic - organic sulfur-containing hydroxyl-containing aromatic- polar basic- polar acidic & amides- polar Non-protein amino acids D-alanine is found in bacterial cell walls neurotransmitters o dopamine , serotonin and melatonin (tryptophan precursor), adrenalin (phenylalanine precursor) o glutamate L-thyroxine is a thyroid hormone--tyrosine precursor L-ornithine is an intermediate in metabolism histamine is one of the causes of allergy symptoms--histidine precursor Sulfur containing amino acids Met, Cys (Met is hydrophobic) Cysteine is weakly polar, methionine is hydrophobic Met (almost always) is first amino acid to be translated in a protein (AUG codon=Met) sulfur group very reactive, important in enzymatic reaction Cys side chain has pK a = 8.3, carries a net negative charge at basic pH Cys can form covalent disulfide bond by oxidation-covalent bond--important in tertiary structure of proteins Aliphatic or Alkane
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