The reaction catalyzed by malate dehydrogenase has a ΔG°′ value of +29.7 kJ⋅mol−1. Given what this says about the occurrence of the reaction catalyzed by malate dehydrogenase in cells explain how the reaction catalyzed by citrate synthase (−31.5 kJ⋅mol−1) influences that activity of malate dehydrogenase. In addition, explain how the activity of citrate synthase functions as a regulatory point for the citric acid cycle

Draw the products of the reaction of xylulose-5-phosphate and erythrose-4-phosphate catalyzed by transketolase in the pentose phosphate pathway. Provide the structure in the protonation state found in physiological conditions. H H H OH FO HO-H H-OH H OPO3²- Q transketolase Draw glyceraldehyde-3- phosphate H H- H H H O OH OH OPO3²- Draw fructose-6- phosphate Q I I

Conversion of F1,6BP to GA3P and DHAP by aldolase is striking in that it is strongly unfavorable when all species are at 1 M (∆G°’ = +22.8 kJ/mol) but favorable when the species are at their physiological conditions (∆G = -5.9 kJ/mol). Based on ∆G°’ and ∆G of aldolase and TIM, and using a reasonable physiological value of 15 mM for the concentration of F1,6BP, calculate the concentrations of GA3P and DHAP under physiological conditions (use T = 37°C). Why is the reaction so much more favorable under these conditions than when all species are at 1 M?

Pyruvate carboxylase catalyzes the first step of gluconeogenesis.   ATP + HCO3─ +  pyruvate  →   oxaloacetate + ADP + Pi   ∆G0’ = ─2.1 kJ mol-1   a) Calculate ΔG for this reaction under the following physiological conditions: 370C, pH 7      [pyruvate] = [HCO3─] = 4.0 mM      [oxaloacetate]= 2.0 mM      [ATP] = 3.5 mM      [Pi] = 5.0 mM      [ADP] = 1.8 mM

ATP, like ADP and AMP, is a competitive inhibitor of NADH binding to malate dehydrogenase. Provide a structural explanation for this inhibition.

Malate dehydrogenase has a ΔGo′ΔGo′= 29.5 kJ/mol for the formation of oxaloacetate from malate yet plays a crucial role in the Citric Acid Cycle. Explain (briefly) how this enzyme with a very non-spontaneous ΔGo′ΔGo′can function well in a biochemical pathway.

All dehydrogenases of glycolysis and the TCA cycle use NAD* (E° for NAD*/NADH is -0.32V) as electron acceptor except succinate dehydrogenase (which uses FAD (E° for FAD/FADH2 is 0.05V). Based on AG° = -NFEº, show and state (1-2 sentences) why is FAD a more appropriate electron acceptor than NAD* in the dehydrogenation of succinate (consider the E° values of %3D Uptake in Na+ Vmax Uptake in absence of Na+ Vmax substrate K: (mM) Kt (mM) L-leucine 420 0.24 23 0.2 D-Leucine 310 4.7 5 4.7 L-valine 225 0.31 19 0.31 fumarate/succinate (E° = 0.031), NAD*/NADH, and the succinate dehydrogenase FAD/FADH2).

[AktivGrid] Draw the product of the reaction of isocitrate catalyzed by isocitrate dehydrogenase in the TCA (citric acid) cycle. Provide the structure in the protonation state found in physiological conditions. 9 H-C-OH 800- -H CH₂ ° Coo of NAD+ dehydrogen isocitrate ase NADH, H*, Drawing CO2

In 1937, two German biochemists published a paper proposing these reactions as part of glucose oxidation: citrate → isocitrate → α-ketoglutarate →succinate → fumarate → malate → oxaloacetate. Adding succinate, fumarate, or malate to thin slices of tissue increased oxygen consumption, supporting the hypothesis that these molecules are intermediates in the process. However, they were puzzled by the observation that these intermediates were still present in the reaction mixture at the end of the experiment. They had thought that intermediates would be consumed as they were converted to the next molecule in the pathway. What explains the observation that these intermediates were still present? a) The pathway is a cycle, constantly regenerating intermediates as glucose is broken down. b) Succinate, fumarate, and malate are not reactants but catalysts, and catalysts are not consumed in the process. c) Succinate, fumarate, and malate increase metabolism and therefore oxygen consumption,…

What is the fate of the radioactive label when each of the following compounds is added to a cell extract containing the enzymes and cofactors of the citric acid cycle and the pyruvate dehydrogenase complex?  P.S. A detailed steps explaination would be greatly appreciated. Also, any tips on how to solve such problems if possible? Is there any particular fate that C atoms of the R group for example, have, at the end of the cycle? I usually think of drawing out each step and solving but I believe that there must be a shorter, smarter way to do it and similar questions. Thank you!