Enzymes: The Catalysts of Life (Chapter 6)

Vocabulary flashcards covering key enzyme concepts and kinetics from the lecture notes.

Enzymes

Protein catalysts that accelerate chemical reactions by lowering activation energy; most are proteins, though some RNA molecules have catalytic activity.

Catalysis

The process by which enzymes increase the rate of a chemical reaction by lowering the activation energy (EA).

Activation Energy (EA)

The energy barrier that must be overcome for a reaction to proceed; enzymes lower EA to speed up reactions.

Transition State

The high-energy intermediate configuration through which reactants pass during a reaction; stabilized by enzymes to lower the energy barrier.

Active Site

Region of the enzyme formed by its folded structure where substrates bind and catalysis occurs.

Substrate Specificity

Enzymes recognize and act on specific substrates due to the shape/chemistry of the active site.

Substrate

Reactant in an enzyme-catalyzed reaction; binds to the enzyme and is converted to product.

Ligand

Molecule that binds to a protein; includes substrates and inhibitors; binding is characterized by affinity and Kd.

Induced-Fit Model

Substrate binding induces a conformational change in the enzyme, enhancing catalysis; more accurate than the lock-and-key model.

Lock-and-Key Model

Old view where the substrate fits a rigid active site like a key in a lock; less accurate than induced fit.

Michaelis-Menten Kinetics

Describes how reaction velocity (v) depends on substrate concentration ([S]); includes concepts of Vmax and Km.

Vmax

Maximum velocity of the reaction when the enzyme is saturated with substrate.

Km (Michaelis Constant)

Substrate concentration at which the reaction rate is half of Vmax; lower Km indicates tighter binding.

Saturation

Condition where increasing [S] no longer increases reaction velocity because the enzyme is fully occupied.

Enzyme Kinetics

Study of the rate of enzyme-catalyzed reactions and factors that affect it.

Lineweaver-Burk Plot

Double-reciprocal plot of 1/v versus 1/[S]; linear with slope Km/Vmax and intercepts giving Km and Vmax.

Competitive Inhibition

Inhibitor competes with the substrate for the active site; increases Km while Vmax remains the same.

Noncompetitive Inhibition

Inhibitor binds to a site other than the active site; decreases Vmax without changing Km.

Inhibitor

Molecule that reduces enzyme activity; can be competitive or noncompetitive.

Regulation of Enzyme Activity

Cellular control of reaction rates by adjusting enzyme levels, activity, and inhibitors.

Affinity (Kd)

Tightness of binding between enzyme and ligand; lower Kd indicates higher affinity and stronger binding.