Biology Enzymes Overview

Enzymes are biological catalysts that increase the rate of chemical reactions without being consumed in the process.

Enzymes are highly specific, meaning they typically catalyze a single reaction or a set of closely related reactions.

Enzymes can accelerate chemical reactions by factors of up to a million or more.

Many enzymes require additional molecules called cofactors for activity. Cofactors can be organic molecules (coenzymes) or metal ions.

Oxidoreductases are enzymes that catalyze oxidation-reduction reactions, involving the transfer of electrons between molecules.

Transferases move functional groups from one molecule to another.

Hydrolases break down molecules by adding water.

Lyases break down molecules without adding water, often forming double bonds.

A group of enzymes that catalyze the transfer of a functional group (e.g., phosphate, amino, or acyl groups) from one molecule to another.

A type of enzyme that breaks down chemical bonds using water (hydrolysis) as a reactant.

Catalyze the cleavage of chemical bonds (C-C, C-O, C-N and others) by other means than hydrolysis and oxidation.

Enzymes that catalyze the rearrangement of atoms within a molecule, converting one isomer into another.

Enzymes that join two molecules together, often using energy from the hydrolysis of ATP.

The energy difference between the transition state and the substrate. The higher the activation energy, the slower the reaction.

Enzymes lower the activation energy by stabilizing the transition state, which speeds up the reaction. Think of it like using a ramp to get over a hill.

The binding energy between the enzyme and substrate contributes to lowering the activation energy. This is like a 'handshake' that makes the reaction easier.

At low substrate concentrations, the initial velocity of the reaction increases almost linearly with an increase in substrate concentration.

At high substrate concentrations, the initial velocity increases by a smaller extent in response to an increase in substrate concentration.

The rate-limiting step in the Michaelis-Menten model is the breakdown of the enzyme-substrate complex (ES) into product and free enzyme.

A plot showing the rate of an enzyme-catalyzed reaction as a function of substrate concentration. It describes how the rate of an enzymatic reaction changes as the concentration of the substrate changes.

The Michaelis constant (Km) is the substrate concentration at which the reaction rate is half of the maximum velocity (Vmax).

The maximum velocity (Vmax) of an enzyme-catalyzed reaction is the rate at which the reaction proceeds when the enzyme is saturated with substrate. This means that all the active sites of the enzyme are occupied.

The Michaelis-Menten equation describes the relationship between the initial velocity of an enzyme-catalyzed reaction, the substrate concentration, and the maximum velocity and Michaelis constant of the enzyme.

The breakdown of the enzyme-substrate complex (ES) to product and free enzyme is a slow step in enzyme kinetics. It determines the overall rate of the reaction.