4a) (10pt) Proline can be synthesized from glutamate as shown below. The first two reactions, glutamate to glutamyl-γ-semialdehyde (glu-γ-SA), are analogous to a set of reactions found in glycolysis but reversed. In other words, a set of two consecutive reactions in glycolysis, if written in reversed, is mechanistically similar to the first two reactions shown. Draw out these two reactions from glycolysis (normal forward direction) with structures and names of reactants and product (predominant form at pH7). Include any cofactors by appropriate name/abbreviations. b) (10pt) The net reaction from glutamate to glutamyl-γ-semialdehyde is shown below. The ∆G’0 for this reaction is +12.2 kJ/mol even coupled to ATP hydrolysis as shown. Describe two factors (strategies) that can contribute to the favorability of this net reaction. 55a) (17pt) The glyoxylate cycle differs from the citric acid cycle (CAC) in that it has two distinct reactions not found in CAC. Those reactions are catalyzed by isocitrate lyase and malate synthase, taking isocitrate to malate in the 2 step/enzyme-catalyzed reactions. Draw out this sequence of reaction with complete structures of reactants, intermediates, products, cofactors (relevant business end) and show reasonable electron pushing mechanism. b) (3pt) What is the net gain (relative to carbon source) in one round of the cycle? 66a) (10pt) In complex I of the electron transport chain, NADH can donate two electrons to FMN to reduce it to FMNH2. The net reaction can be written as NADH + H+ + FMN Æ NAD+ + FMNH2. Illustrate this net reaction by drawing out the appropriate structures (business ends of reactants and products) and show the two electron pushing chemistry involved. b) (10pt) In the next sequence of electron transfer, FMNH2 donates two electrons, one at a time, through a series of Fe-S centers which eventually reduces Q to QH2. The net reaction can be written as FMNH2 + Q Æ FMN + QH2. Illustrate this net reaction by drawing out the appropriate structures (business ends of reactants, intermediates, and products) and show how FMNH2 can donate electrons, one at a time, directly to Q to form QH2 + FMN. c) (10pt) The net transfer of electrons through complex I can be written as NADH + H+ + Q Æ NAD+ + QH2. Using the information on page 1, calculate the ∆G’0 of this net reaction. 77a) (8pt) A strain of yeast (a eukaryotic organism) was discovered which is able to utilize D-glyceraldehyde as a carbon (fuel) source by first converting it to glyceraldehyde-3-phosphate. Propose the most likely mechanism of reaction for this first step based on your knowledge of the reactions seen in class. Show all structures of reactant(s) and product(s), cofactors (business end), and electron pushing mechanism involved. b) (8pt) Under anaerobic condition, this organism can ferment D-glyceraldehyde to ethanol. What is the net ATP yield (or equivalents) per round of fermentation? Explain your logic/reasoning/assumption(s) to account for your answer for full credit. c) (8pt) If D-glyceraldehyde was 14C-radio-labeled at carbon number 3, what carbon(s) in ethanol would be label, if any? Draw out the structure of ethanol and clearly indicate the labeled carbon(s) with an asterisk or arrow. 89d) (8pt) Under aerobic condition, this organism can completely oxidize glyceraldehyde to CO2. What is the net ATP yield (or equivalents) for two rounds of oxidation? Explain your logic/reasoning/assumption(s) to account for your answer for full credit. e) (8pt) In the first round of oxidation, which carbon(s) on α-ketoglutarate would be labeled, if any? Draw out the structure of α-ketoglutarate and clearly indicate the labeled
View Full Document
Unlocking...