Description
homework
1) The concentrations of ATP, ADP, and AMP in a particular rat hepatocyte cell are 3.38 mM, 1.32 mM, and 0.29 mM, respectively. Using the information you used in problem 9, calculate the Gibbs Free Energy (ΔG) for the reaction
ATP + AMP ⇌ 2 ADP
under these conditions at 37°C. Give your answer in kJ/mol to one decimal (tenths) without units.
2) Given the the standard reduction potentials for cystine disulfide and NAD+ on Table 1 below, calculate the standard state reduction potential for the chemical reaction that follows. Give your answer in Volts to three decimals (thousandths) and do not include units.
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Table 1. Standard Reduction Potentials of Some Biochemically Important Half-Reactions |
|
|
Half-Reaction |
Δℰ°’ (V) |
|
NAD+ + H+ + 2e– ⇌ NADH |
-0.315 |
|
Cystine disulfide + 2H+ + 2e– ⇌ 2 Cysteine |
-0.340 |
Cystine disulfide + NADH + H+ ⇌ 2 Cysteine + NAD+
3) A healthy cell produces ATP continuously. However, ATP is only one of four ribonucleoside triphosphates (together with CTP, GTP, and UTP) required in roughly equal amounts for synthesis of all the RNA in a cell (and there is a lot of RNA in a cell!). Which enzyme is responsible for maintaining the roughly equal cellular concentrations of the four ribonucleoside triphosphates?
a) Inorganic pyrophosphatase
b)Ribonuclease
c) Nucleoside diphosphate kinase
d) Chymotrypsin
4)Draw a schematic diagram for the steps leading up to the removal of two electrons from glyceraldehyde-3-phosphate to NAD+ by the enzyme GAP dehydrogenase. How does this dehydrogenation differ from similar reactions catalyzed by lactate dehydrogenase or yeast alcohol dehydrogenase. What is the advantage of using the mechanism of GAP dehydrogenase? (HINT: think of the role played by Pi in the GAP dehydrogenase enzyme mechanism
5) Use the half reaction reduction potentials found on Table 14-4 to calculate the standard state Gibb’s Free Energy (ΔG°’) for the reaction: (picture attached of chart)
Pyruvate + NADH + H+ ⇌ Lactate + NAD+
If the steady state cellular concentrations of Pyruvate and Lactate are held fixed at 0.051 mM and 0.51 mM, respectively, then what is the ratio of [NAD+]/[NADH] below which this reaction begins to be energetically favorable at 37°C? Note that for this reaction the H+ ions are immediately buffered by proteins, metabolites, other small molecules, and even water in the cell cytoplasm so, effectively, they are available as needed and “disappear” as soon as they are produced. Therefore, you need not include the [H+] in your free energy calculations
6) Neatly create a diagram that shows each of the ten steps in glycolysis. Include the structures and names of each of the stable intermediates, the names of each of the enzymes, and the co-factors (ATP, NAD+) required and generated in the pathway.
