CHM 635 1st Exam 2012 Key

CHM 635 1st Exam 2012 Key - CHM 635 First Midsem, Spring...

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CHM 635 First Midsem, Spring 2012 Each question is worth 10 points 1. (a) What produces proton motive force in the mitochondria? (4 points) Proton motive force can be described as the storing of energy as a combination of a proton and voltage gradient across a membrane. Proton gradient has lots of potential energy When the energy is released (protons flow back into matrix through ATP synthase), the energy drives ATP synthesis (b) Why ATP is a high energy molecule (3 points) 1. Chemical contribution G chem = n RT ln ([H + ] in / [H + ] out ) (n = number of protons translocated) 2. Electrical contribution:  = membrane potential G elect = zF  (z = charge (1.0 for H + ), F =96,485 JV 1 mol 1 )
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Provide two reasons why liver is able to provide glucose to the brain during starvation, but not the muscles? (3 points) (i) Via gluconeogenesis, which only occurs in liver. (ii) By dephosphorylating glucose-6-phosphate to glucose, which occurs in liver ER, due to the presence of glucose-6-phosphate phosphatase. Glucose-6-phosphate phosphatase is absent in the muscles. 2. How different steps of glycolysis are allosterically and hormonally regulated? (10 points) 1. Hexokinases: inhibited by excess glucose 6-phosphate . 2. PFK1: allosterically inhibited by ATP and citrate and activated by AMP and F-2,6-bisphosphate. AMP and fructose 2,6- bis phosphate (F2,6BP) relieve the inhibition of PFK-1 by ATP 3. Pyruvate Kinase: regulated by Fructose 1, 6-bisphosphate and by phosphorylation. 3. (a) Why cancer cells show Warburg effect, instead of Pasteur Effect? Provide three reasons. (6 points)
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CHM 635 1st Exam 2012 Key - CHM 635 First Midsem, Spring...

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