Enzymes: Catalysts, Regulation, and Mechanisms

Enzymes

Biological catalysts that speed up reactions.

Activation Energy (EA)

Energy required to initiate a chemical reaction.

Metastable State

Condition where reactions are thermodynamically feasible but slow.

Hydrolysis of ATP

Reaction yielding ADP and Pi with ΔG = -7.3 kcal/mol.

Isothermal

Constant temperature condition in biological systems.

Kinetic Energy

Energy of motion influencing reaction rates.

Catalyst

Substance that increases reaction rate without being consumed.

Transient Complex

Temporary association between enzyme and substrate.

Equilibrium Position

State where reactants and products are balanced.

Ribozymes

RNA molecules with catalytic activity.

Active Site

Region on enzyme where substrates bind.

Enzyme Specificity

High affinity of enzymes for specific substrates.

Induced-Fit Model

Enzyme changes shape to accommodate substrate.

Conformational Change

Structural alteration of enzyme upon substrate binding.

Cofactors

Nonprotein molecules aiding enzyme function.

Prosthetic Groups

Tightly bound cofactors, often metal ions.

Coenzymes

Organic cofactors derived from vitamins. enzyme regulation

Enzyme Inhibition

Reduction of enzyme activity by inhibitors.

Irreversible Inhibitors

Covalently bind and permanently deactivate enzymes.

Reversible Inhibitors

Noncovalently bind and can dissociate from enzymes.

Competitive Inhibitors

Compete with substrate for active site access.

Noncompetitive Inhibitors

Bind to enzyme regardless of substrate presence.

Enzyme Regulation

Adjusting enzyme activity to meet cellular needs.

Substrate-Level Regulation

Regulation based on substrate and product concentrations.

Allosteric Regulation

Control mechanism altering enzyme activity through binding.

Feedback Inhibition

End product inhibits an earlier step in pathway.

Covalent Modification

Regulation by adding or removing chemical groups.