Aconitase catalyzes the reaction: citrate isocitrate The standard free energy change, G°², for this reaction is +

Aconitase catalyzes the reaction: citrate ‡† isocitrate
The standard free energy change, ˆ†G°€², for this reaction is + 6.3 kJ / mol however, the observed free energy change (ˆ†G) for this reaction in mammalian mitochondria at 25°C is ˆ¼ 0 kJ/mol (Table 13.2).
(a) Calculate the ratio of [isocitrate] / [citrate] in mitochondria.
(b) Is this reaction likely to be a control point for the citric acid cycle? Why or why not?

Transcribed Image Text:

TABLE 13.2 Reactions of the citric acid cvcle Reactiorn Enzyme AG (kJ/mol) -55 (kJ/mol) 1. 2a. | Citrate cis-aconitate + H2O 2D.CIS-Aconitate+ H 3 4 Acetyl-CoAoxaloacetateH2Ocitrate CoA-SHH 32.2 Citrate synthase Aconitase Aconitase Isocitrate dehydrogenase α-Ketoglutarate dehydrogenase complex +6.3 isocitrate IsocitrateNAD+ a-ketoglutarate + CO2 + NADH -20 a-Ketoglutarate + NAD CoA-SH succinyl-CoA + CO2 + NADH 33.5 -40 5. Succinyl-CoA PADP (GDP) 6. Succinate FAD (enzyme-bound) 7. 8 succinate ATP (GTP) CoA-SH Succinyl-CoA synthetase 3.8 fumarate FADHz (enzyme-bound) Succi nate dehydrogenase 0 FumarateH2O L-Malate + NAD+--oxaloacetate + NADH + H+ 3.8 +29.7 -48.0 L-malate Fumarase Malate dehydrogenase Net -115