Midtm2005Answ - METABOLIC BIOCHEMISTRY Immo E Scheffler...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
METABOLIC BIOCHEMISTRY Winter 2005 Immo E. Scheffler 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 **********************************************************************************
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
QUESTION 1 a) (5 points) Give the structural formula for NAD + ; show also the reduced form with only the “business end” of the molecule. 4 points for the complete, correct structure of NAD+, and one point for showing the correct reduced nicotinamide b) (4 points) Illustrate the use of this cofactor with the final reaction in glycolysis catalyzed by lactate dehydrogenase (structural formulae required for the two small carbon compounds). pyruvate + NADH + H + lactate + NAD + structural formulae required for pyruvate and lactate one point for the equation, three points for the correct structures c) ( 6 points ) The rate of such a reaction is to be measured, using a spectrophotometer. The progress of the reaction can be followed because the absorption spectrum of the substrate/cofactor is changed when it is oxidized. Explain briefly with a highly schematic diagram and a brief description of the measurement. The absorption spectra of the oxidized and reduced forms of NAD/NADH differ (see above); the biggest difference is at a wavelength of 340 nm. Hence the reaction can be followed by measuring
Background image of page 2
the absorbance at 340 nm. When NADH is used up, the absorbance will decrease, since the product NAD + does not absorb appreciably at this wavelength. d) ( 3 points ) If [1- 14 C] pyruvate is given to a yeast extract, would you expect to be able to obtain radioactive ethanol? Explain your answer with the help of structural formulae In the conversion of pyruvate to ethanol and CO 2 a decarboxylation reaction is the first reaction. In the decarboxylation reaction the carbon-1 of pyruvate (the carboxyl group) is lost. No radioactive ethanol would be obtained. The structure of pyruvate should be shown and the No. 1 carbon (carboxyl group) should be shown as the source of radioactive CO 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
QUESTION 2 A kinetic scheme for an enzyme catalyzed reaction has been formulated by Michaelis and Menten. It makes an assumption about the steady state concentration of an enzyme-substrate intermediate. An expression for the initial rate (v o ) of the reaction can be derived as follows: k 2 [E total ] [S] V o = -------------------------- (k 2 +k -1 )/k 1 + [S] a ) ( 4 points ) show the reaction sequence on which M&M based their derivation and assign rate constants to the elementary steps k 1 E + S k 2 E-S E + P k -1 b ) ( 1 points ) what is the expression for K
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 17

Midtm2005Answ - METABOLIC BIOCHEMISTRY Immo E Scheffler...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online