Figure 2-27. Hypothetical energy changes in the conversion of a reactant — say, glyceraldehyde 3-phosphate (G3P) — to a product — say, dihydroxyacetone phosphate (DHAP) — in the presence and absence of a catalyst.

Figure 2-27Hypothetical energy changes in the conversion of a reactant — say, glyceraldehyde 3-phosphate (G3P) — to a product — say, dihydroxyacetone phosphate (DHAP) — in the presence and absence of a catalyst

The trough in each curve represents a stable intermediate in the reaction, as depicted in Figure 2-28. The total activation energyG) is the difference between the free energy of the reactants and that represented by the highest crest along the pathway. A catalyst accelerates the rate of a reaction by reducing the free energy of the transition state, so that the activation energy of the catalyzed reaction, ΔGcat, is less than that of the uncatalyzed reaction, ΔGuncat. Catalysts do not alter the free energy of reactants or products or affect their equilibrium concentrations.

From: Section 2.5, Activation Energy and Reaction Rate

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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