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HW3 KEy - Provide your answer in the form of an equation...

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CHEM 4731/5731 Name: ______KEY Problem Set #3: Amino acid metabolism ________________ Due in class Tuesday, February 8, 2011 1. (4 points) Calculate the net ATP yield (ATP equivalents) for the combined complete oxidation of 1 molecule of serine and 1 molecule of alanine to CO 2 in the liver, taking into consideration the energy cost of nitrogen excretion as urea. Show your reasoning. (Assume GTP = ATP) Work out a pathway that uses the nitrogen in each amino acid for the nitrogens in the excreted urea without the input of additional nitrogen. 2. (2 points) Under some conditions, threonine can serve as a substrate for serine hydroxymethyl transferase. From your knowledge of the mechanism of this enzyme, propose the substrates and products for this reaction.
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Unformatted text preview: Provide your answer in the form of an equation, stating cofactors and drawing the input amino acid and its products. 3. (4 points) The first half of the mechanism for PLP-dependent enzyme-catalyzed transamination of amino acids is shown in the notes. Draw a mechanism for the second half of the reaction. Show structures of substrates, cofactors, intermediates and products, except the enzyme itself which can be designated “E”. Use arrows to indicate movement of electrons. 4. (2 points) A mouse ingests glycine labeled on the alpha carbon with 14 C. Which carbon(s) in newly synthesized serine can be labeled with 14 C soon after the glycine is ingested? Draw serine below and circle the potentially labeled carbon(s)....
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