AP Biology Unit 3: Cellular Energetics — Master Guide to Enzymes

Enzyme

A macromolecule that acts as a biological catalyst, speeding up chemical reactions without being consumed.

Catalyst

An agent that accelerates a chemical reaction without being consumed by the reaction.

Active Site

A specific region on the enzyme where the substrate binds, with properties that must match the substrate.

Substrate

The specific reactant that an enzyme acts upon.

Specificity

The ability of an enzyme to catalyze a specific reaction for a particular substrate.

Lock and Key Model

An outdated model of enzyme-substrate interaction where the active site is considered a rigid structure.

Induced Fit Model

A model describing how an enzyme changes shape when a substrate binds, enhancing its catalytic ability.

Activation Energy (E_A)

The initial investment of energy required to start a chemical reaction.

Transition State

An unstable state during a chemical reaction where reactants must overcome an energy barrier.

Denaturation

The process by which proteins lose their functional shape due to environmental changes, such as high temperature.

Optimum Temperature

The temperature at which an enzyme's reaction rate is fastest.

Optimum pH

The specific pH level at which an enzyme is most active.

Cofactors

Inorganic ions required by some enzymes for their activity.

Coenzymes

Organic molecules that assist in enzyme function, often derived from vitamins.

Competitive Inhibition

An inhibition type where an inhibitor binds to the active site, preventing substrate access.

Noncompetitive Inhibition

An inhibition type where an inhibitor binds to an allosteric site, altering the enzyme's shape.

Allosteric Regulation

A regulatory process where a molecule binds to a protein at one site and affects its function at another site.

Vmax

The maximum rate of reaction that can be achieved by an enzyme when it is saturated with substrate.

Hydrophobic Environment

A microenvironment created by enzymes that favors reactions involving nonpolar substrates.

Hydrogen Bonds

Weak interactions important for maintaining the 3D shape of enzymes.

Ionic Bonds

Chemical bonds that may be disrupted by changes in pH, affecting enzyme configuration.

Thermal Agitation

Movement of molecules that can disrupt bonds in proteins at high temperatures, leading to denaturation.

R-groups

Side chains of amino acids that play a key role in the chemical properties and interactions of enzymes.

Saturation Point

The point at which all active sites of an enzyme are occupied, and adding more substrate does not increase reaction rate.

Equilibrium

The state in a chemical reaction where the rates of the forward and reverse reactions are equal, unaffected by enzymes.

Molecular Motion

The movement of molecules which influences enzyme activity, particularly at varying temperatures.