scheffler midterm

scheffler midterm - METABOLIC BIOCHEMISTRY BIBC102 Winter...

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METABOLIC BIOCHEMISTRY BIBC102 Immo E. Scheffler Winter 2008 MIDTERM EXAM All answers are to be written into the Blue Book. Leave the first inside page blank for scoring. There are 10 questions. Make sure that each answer is clearly identified with the question number at the top or left side of the page. Useful Information: Avogadro's number: 6.02 x 10 23 molecules / mole 1 Faraday = 96,494 Coulomb / mole = 96,494 Joules / Volt / mole Gas constant (R) = 8.31 Joules K -1 mol -1 = 1.987 cal K -1 mol -1 = 0.082 liter atm K -1 mol -1 1 calorie = 4.184 Joules ********************************************************************************** QUESTION 1 (15 Minutes) a) [2] Explain in a few word what we mean by the active site of an enzyme it is a site of/on the enzyme where substrates bind and interact with key amino acid side chains required for binding and catalysis
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b) [2] Describe in a few words what we mean by the turnover number of an enzyme the turnover number of an enzyme is the number (moles) of substrate molecules converted to product per second per molecule (mole) of enzyme when the substrate concentration is not limiting (i.e. is infinite) c) [4] How is the turnover number determined experimentally? One measures v max , and knowing the enzyme concentration one can calculate the turnover number (k cat ). v max = k cat x [E T ] where [E T ] is the known, total enzyme concentration; d) [4] What do we mean by a competitive inhibitor of an enzyme? (a few words and a labeled diagram are needed for the answer). A competitive inhibitor is structurally similar to the substrate and binds to the active site of the enzyme, competing with the substrate e) [3] What is feedback inhibition and why is it significant in metabolic pathways? A frequent control mechanism is to have the final product of a metabolic pathway act as an inhibitor of a key regulatory enzyme at or near the beginning of the pathway. The inhibition is typically non- or un-competitive, since the inhibitor is likely very different from the substrate. When the end product is abundant, it save substrate at the beginning of the pathway and allows it to be used for other pathways. QUESTION 2 (8 min) Cyclic AMP is a positive modulator of a class of protein kinases a) [4] Write down the complete structural for cyclic AMP (cAMP).
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b) [4] Explain, with the help of a schematic diagram how cAMP affects the activity of the cAMP- dependent protein kinase the cAMP-dependent protein kinase has regulatory and catalytic subunits associated in an
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This note was uploaded on 09/11/2009 for the course BIBC 2314 taught by Professor Scheffler during the Spring '09 term at UCSD.

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scheffler midterm - METABOLIC BIOCHEMISTRY BIBC102 Winter...

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