Description
Work out the following problems.
- Calculate the energy yield or cost, in ATP equivalents, for the following processes:
- glycogen (3 residues from one nonreducing end) ? 6 pyruvate
- 3 glucose ? 6 pyruvate
- 6 pyruvate ? 3 glucose
- Neatly draw the structure of a single molecule of glycogen that contains at least 22 glucose monomers and two branch points. Label your branch points as well as your reducing and non-reducing ends.
- Name the enzymes required for glycogen synthesis and the balanced chemical reaction catalyzed by each enzyme. Do the same for the enzymes involved in breakdown of glycogen.
- Write out the first two steps of gluconeogenesis as balanced chemical reactions. Then add them together to generate one net chemical reaction. What reaction from glycolysis do these two reactions replace? Why does it require two reactions and two enzymes to make it energetically favorable to run this reaction in reverse? Why is it that reactions 9 and 11 of gluconeogenesis are energetically favorable despite the fact that the reactions with which they correspond in glycolysis (reactions 1 and 3) are also energetically highly favorable?
- Write a sequence of balanced reactions (intermediates and enzymes) for the catabolism of six molecules of glucose-6-phosphate by the pentose phosphate pathway followed by conversion of ribulose-5-phosphate back to glucose-6-phosphate by gluconeogenesis. What is the net reaction (reactants in equilibrium with products) for this cycle?
