The table below lists factors that regulate metabolite flow through the pyruvate dehydro-genase complex and the tricarboxylic acid cycle. Indicate for each enzyme or enzyme complex listedwhether each metabolite activates (1), down-regulates (↓), or has no effect (±) on the catalytic actionof the enzyme. For the last row indicate whether the AG for the reaction is < 0, > 0, or ~ 0 whereAG = AGO! + RT In I, AG°' being the standard free energy change for the reaction at pH 7 and25° C and I is the mass-action ratio representing the ratio of the actual concentrations of the reactionproducts to the actual concentrations of the reactants.ATPADPNAD+NADHsuccinyl-SCOACa²+CH3CO-SCOATPPkinasephosphataseAGPyruvate dehy-drogenasecomplexIsocitratedehydrogenasea-ketoglutaratedehydrogenasecomplexMalate dehydro-genase

Answered: The table below lists factors that…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Question

The table below lists factors that regulate metabolite flow through the pyruvate dehydro-
genase complex and the tricarboxylic acid cycle. Indicate for each enzyme or enzyme complex listed
whether each metabolite activates (1), down-regulates (↓), or has no effect (±) on the catalytic action
of the enzyme. For the last row indicate whether the AG for the reaction is < 0, > 0, or ~ 0 where
AG = AGO! + RT In I, AG°' being the standard free energy change for the reaction at pH 7 and
25° C and I is the mass-action ratio representing the ratio of the actual concentrations of the reaction
products to the actual concentrations of the reactants.
ATP
ADP
NAD+
NADH
succinyl-SCOA
Ca²+
CH3CO-SCOA
TPP
kinase
phosphatase
AG
Pyruvate dehy-
drogenase
complex
Isocitrate
dehydrogenase
a-ketoglutarate
dehydrogenase
complex
Malate dehydro-
genase

Expert Solution

Regulation of metabolic flux

There are a wide variety of metabolic pathways that can take place within a cell. Hence , one molecule could get metabolized via different pathways. It is by regulating the enzymes participating in these metabolic pathways, the cell decides to which metabolic pathway a biomolecule should be directed towards under a particular condition.

Enzymes can be regulated by substrate availability, feedback inhibition by products, allosteric regulation and intrinsic protein modifications like phosphorylation/dephosphorylation, etc.

A negative $∆ G$ value indicates that the reaction is energetically favorable, while a positive value indicates that the reaction is energetically unfavorable to take place. A $∆ G$ value of 0 indicates that the reaction is in equilibrium.