Chapter 3 Glossary

Enzyme

an organic molecule, typically a protein, that catalyses (speeds up) specific reactions

Catalyst

a substance capable of increasing the rate of a reaction without being used up

Catalyse

 to increase the rate of a reaction

Substrate

the reactant of a reaction catalysed by an enzyme

Reactant

 a molecule that undergoes a transformation into a product. When enzymes are involved, the reactant is called a substrate

Product

the transformed molecule created in a reaction

Active Site

the part of an enzyme where the substrate binds

Enzyme - Substrate Complex

the structure formed when an enzyme and substrate are bound together

Conformational Change

  a change in the three-dimensional shape of macromolecules such as proteins

Activation Energy

 the energy required to initiate a reaction

Collision Theory

explanation of chemical reactions that states that in order to react molecules must hit one another

Optimal

the point at which for a given condition (e.g. temperature), the maximum function of an enzyme occurs. Also known as optimum.

Denature

the disruption of a molecule’s structure by an external factor such as heat

Saturation Point

the point at which a substance (e.g. an enzyme) cannot receive more of another substance (e.g. a substrate)

limiting factor

a factor that prevents the rate of reaction from increasing

Limiting Reagent

a reactant that prevents the rate of reaction from increasing

Enzyme inhibitor

a molecule that binds to and prevents an enzyme from functioning

Competitive inhibition

the hindrance of an enzyme by blocking the active site and preventing the substrate from binding

Non-competitive inhibition

the hindrance of an enzyme by binding to an allosteric site and changing the shape of the active site to prevent the substrate from binding

Allosteric site

a region on an enzyme that is not the active site

Reversible inhibition

enzyme inhibition that involves weaker bonds that can be overcome

Irreversible inhibition

enzyme inhibition that involves stronger bonds that cannot be broken

Biochemical Pathway

 a series of enzyme-catalysed biochemical reactions in which the product of one reaction becomes the substrate of the next reaction. Also known as a metabolic pathway

Cofactor

any organic or inorganic molecule, such as a coenzyme or metal ion, that assists enzyme function

Coenzyme

a non-protein organic cofactor that assists enzyme function. They release energy and are recycled during a reaction

ATP

adenosine triphosphate, a high energy molecule that, when broken down, provides energy for cellular processes

ADP

adenosine diphosphate, the unloaded form of ATP