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UIUC MCB 450 - shortA-key-1

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Name: __________________________________ NetID:_________________________ 1 30. (2 pts) What is the thermodynamically favorable direction( /) of each of the following two reactions when the reactants are initially present in equimolar amounts? Circle one arrow ( or ) for each reaction: (Reaction 1) ATP + creatine  ?  creatine phosphate + ADP (Reaction 2) ATP + glycerol  ?  glycerol 3-phosphate + ADP 31. (4 pts) The reactions catalyzed by hexokinase and phosphofructokinase have ∆G’°s of –16.7 and –14.2 kJ/mol, respectively, and, because of these relatively high negative ∆G’°s, either enzyme could be used to regulate glycolysis (eg. by allosteric inhibition). In most cells, however, one of these enzymes is not used to regulate glycolysis. Which enzyme is not regulated, and why is this enzyme not used as a control site? (2 pts) Hexokinase is not used to regulate glycolysis since the product of hexokinase (glucose-6-phosphate) is used by pathways other than glycolysis (PPP and glycogen synthesis). (2 pts) Inhibition of hexokinase would also inhibit these other pathways in addition to glycolysis. PFK is the first non-reversible enzyme in glycolysis whose product is specific to glycolysis. - give extra credits if say that hexokinase is allosterically regulated in muscles by high G6P. ATP à ADP + Pi ∆G= -30.5 kJ/mol Creatine phosphate à creatine + Pi ∆G = -43.3 kJ/mol Glycerol-3 phosphate à glycerol + Pi ∆G = -9.2 kJ/molName: __________________________________ NetID:_________________________ 2 32. (7 pts.) In class, I have made an analogy between the blood glucose regulation and the heating/ cooling system of a home. Describe or draw a diagram showing how the body regulates high blood sugar levels after eating a chocolate bunny. Include the name of the organs and hormones involved, and their role in blood glucose regulation. Make sure to also include how the rates of glycolysis and gluconeogenesis are affected. (1 pt) -Liver: furnace/AC/ removes from or add glucose to blood. (accept any of these descriptions) -Pancreas (thermostat/glucostat) /blood glucose sensor. (accept any of these descriptions) (1pt) -High blood sugar causes release of insulin from pancreas (1pt)- insulin stimulates liver to take up glucose (1 pt)- insulin turns off pathways to make glucose (1 pt)- Blood sugar levels go back to normal (1 pt) glycolysis – up (1 pt) gluconeogenesis (down)Name: __________________________________ NetID:_________________________ 3 33. (4 pts) Fructose can be converted to pyruvate by glycolysis. However, the point of entry of fructose into the glycolytic pathway depends on tissue type. Compare the point(s) of entry of fructose in adipose tissue to that of liver cells. (2pts) In the liver, Fructose enters glycolysis by first being converted to GAP and DHAP (2 pts) In adipose tissues, fructose enters glycolysis by getting phosphorylated to F6P 34. (2 pts) List two molecules that can be converted to glucose (other than the gluconeogenesis intermediates) by the gluconeogenesis pathway? Certain amino acids Alanine Lactate Glycerol 35. (4 pts) Give two reasons as to why the gluconeogenesis pathway could not simply be the same enzymatic reactions as glycolysis but in reverse. (2 pts)The ∆G for the overall glycolysis pathway is very negative (~-96 kJ/mol). If gluconeogenesis was to use the same enzymes as glycolysis (but in reverse), it would have a large +∆G value, therefore it would be thermodynamically unfavorable. (2pts) Sharing of the exact same enzymes between two pathways (but in reverse) would prevent the reciprocal regulation of the pathways.Name: __________________________________ NetID:_________________________ 4 36. (6 pts) The degradation of alanine yields pyruvate, and the degradation of leucine yields acetyl CoA. Can the degradation of these amino acids replenish the pool of citric acid cycle intermediates, more specifically, oxaloacetate? Explain. Circle one: (1pt) Alanine: Yes /No (2 pts) Why? Pyruvate can be converted directly to oxaloacetate, which can be used to generate oxaloacetate by the enzyme pyruvate carboxylase. (1 pt)Leucine: Yes/No (2 pts) Why? No, acetyl CoA cannot be converted to oxaloacetate in the TCA cycle. At the beginning of the TCA cycle, oxaloacetate is condensed with acetylCoaA, generating citrate. At the end of the cycle, oxaloacetate is recycled. NO new oxaloacetate is generated by the entry of acetyl Coa into the TCA cycle. Could also get full credit if said : Yes, two molecules of acetylCoA could be used to make one new OAA via the the glycoxylate cycle but only in plants and prokaryotes. 37. (5 pts total) Answer the following: (a) (1 pt) Using the table below, determine whether the following reactions will proceed as written. Indicate (Yes) or (No). Ethanol + Blue → acetaldehyde + Orange + 2 H+ YES or NO (Circle one) (b) (4 pts) Calculate ∆Go’ for the above reaction. F=96.5 kJ/V. mol.Name: __________________________________ NetID:_________________________ 5 (2 pts for finding the redox value) Since ∆ζ°’= +0.2 + (-0.05) = + 0.15 V ∆G°’= - nF∆ζ°’ ∆Go’ = -2 x 96.5 kJ/V. mol x 0.15 V = -28.95 kJ/mol (2 pts for finding the ∆G value; could still get the 2 pts for finding the ∆G even if it was calculated using the wrong redox value as determined beforehand) oxidant reductant n E’o(V) acetaldehyde ethanol 2 - 0.20 Blue Orange 2 - 0.05 -END OF


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UIUC MCB 450 - shortA-key-1

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