Ptest3

Ptest3 - BCH 4054 October 16, 1998 PRE-TEST 3 GROUP NAME _...

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BCH 4054 October 16, 1998 PRE-TEST 3 GROUP NAME ____________________ This test is take-home and open book, and it is intended that all members of the group contribute to completing it. Only one copy is to be submitted by the group, and all members who participated should sign their names below. Test is due at the end of class on Monday, October 26. Please use dark pencil or ink and write legibly. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ Page Points 1 ______ 2 ______ 3 ______ 4 ______ 5 ______ Total ______ Points 1. Glutamine synthetase is regulated in bacteria both by allosteric end-product inhibition and by covalent modification. (2) (a) What type of covalent modification is involved? (2) (b) Is the modified enzyme the active or inactive form? (4) (c) The state of the enzyme (modified or unmodified) depends on the concentrations of glutamine and of alpha-ketoglutarate. Explain how these compounds regulate the modification of the enzyme. (4) 2. Tetrahydrofolic acid (THFA) exists in several derivative forms: (a) N 10 -formyl-THFA (b) N 5 -N 10 -methylene-THFA (c) N 5 -N 10 -methenyl-THFA (d) N 5 -methyl-THFA Which of these forms (identify by putting the correct letter or letters in the blank) ____ is formed in the degradation of serine? ____ furnishes the methyl group in methionine biosynthesis?
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Ptest3 - BCH 4054 October 16, 1998 PRE-TEST 3 GROUP NAME _...

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