Biology Enzymes Overview

Study Notes

Enzyme Overview

Enzymes are biological catalysts that enhance the rate of chemical reactions without changing thermodynamic properties.
Most enzymes are proteins, providing specificity and efficiency in catalyzing reactions.
Enzyme kinetics reveals the affinity of enzymes for substrates and informs about reaction rates.
Regulation of enzymes occurs through molecules produced by cells or drugs, modifying activity levels.

Enzyme Function

Enzymes bind to substrates, forming or breaking covalent bonds quicker than uncatalyzed reactions.
They lower activation energy (Ea) needed for reactions, but do not alter free energy change (delta G) or reaction direction.

Catalysis Dynamics

Catalysts accelerate reactions in both directionalities, expediting system equilibrium without altering it.
Enzyme specificity dictates efficient catalysis based on enzyme affinity for reactants vs. products.
Examples include phosphoglucomutase, an enzyme moving phosphate groups in glucose metabolism.

Substrate Binding and Induced Fit

Enzymes exhibit an active site where substrates bind; this specificity is key for optimal function.
Binding induces conformation changes in enzymes (induced fit model), facilitating reaction.
Substrate binding involves physical forces like hydrogen bonds and shapes may change during the reaction.

Mechanisms of Lowering Activation Energy

Enzymes promote substrate proximity, apply physical strain, and can alter charge distributions to enhance reactivity.
Efficiency varies; some enzymes work preferentially in one reaction direction based on substrate concentrations.

Reaction Kinetics

Kinetics studies how enzyme-catalyzed reaction rates change over time and with varying substrate concentrations.
Reaction rates can show a maximum speed (Vmax) at high substrate concentrations when all enzymes are saturated.

Vmax and Km

Vmax represents the maximum rate of an enzyme-catalyzed reaction, influenced by enzyme concentration and environmental conditions.
Km (Michaelis constant) reflects substrate concentration at which an enzyme is at half its maximum velocity, indicating enzyme affinity—lower Km signifies higher affinity.

Effects of Substrate Concentration and Enzyme Saturation

Increasing substrate concentration enhances reaction rate until a plateau (Vmax) is reached, indicating enzyme saturation.
Without enzymes, reaction speeds are slower, demonstrating the crucial role of enzymes in biological processes.

Enzyme Regulation

Enzymes are tightly regulated to avoid continuous activity, maintaining necessary levels of biochemical reactions.
Allosteric regulators alter enzyme activity by changing the shape of the active site, which can either inhibit or activate enzymatic action.

Inhibitors

Reversible inhibitors, including competitive and non-competitive, bind temporarily and can affect rates of catalysis.
Competitive inhibitors block the active site directly, while non-competitive inhibitors alter enzyme function without directly blocking the site.
Irreversible inhibitors form permanent bonds with enzymes, inhibiting their activity and often leading to cell toxicity.

Penicillin as an Irreversible Inhibitor

Functions by covalently binding to bacterial enzymes, interrupting cell wall synthesis, effective mainly against gram-positive bacteria.
Works through inhibiting glycopeptide transpeptidase, crucial for peptidoglycan formation in bacterial cell walls.

Description

Explore the fascinating world of enzymes as biological catalysts. This quiz covers key concepts such as enzyme kinetics, regulation, and the role of enzymes in increasing the rates of chemical reactions. Ideal for students studying biology.