Introduction to Cellular Energy Vocabulary

Free energy (G)

The proportion of a system's energy that can do work at constant temperature and pressure.

Chemical energy

energy stored in the bonds of molecules

entropy (S)

a measure of disorder or randomness is a system; energy unavailable to do work

activation energy (Ea)

the minimum energy required to start a chemical reaction

transition state

the high-energy, unstable state of reactants during a chemical reaction before forming products

enzyme

a protein that speeds up a chemical reaction by lowering activation energy without being consumed

catalyze

to accelerate a chemical reaction using an enzyme

active site

the specific region on an enzyme where the substrate binds and the reaction occurs

substrate

the reactant molecule that an enzyme acts on

activator

a molecule that increases enzyme activity, often by binding to the enzyme and stabilizing its active form

irreversible inhibitor

a molecule that permanently binds to an enzyme, preventing it from functioning

reversible inhibitor

a molecule that temporarily binds to an enzyme, reducing its activity without permanent damage

competitive inhibitor

a reversible inhibitor that binds to the enzyme's active site, competing with the substrate

noncompetitive inhibitor

a reversible inhibitor that binds to a site other than the active site, changing tha enzyme's shape and reducing activity

ATP (Adenosine Triphosphate)

The main energy currency of the cell; releases energy when phosphate bonds are broken

ADP (Adenosine Diphosphate)

The product formed when ATP loses a phosphate group; can be recycled back to ATP

Phosphate group (Pi)

An inorganic phosphate; high-energy bond in ATP that releases energy when hydrolyzed

Oxidized electron carrier

a molecule that can accept electrons during a redox reaction (NAD+ is the oxidized form of NADH)

Reduced electron carrier

A molecule that has gained electrons in a redox reaction (NADH is reduced form of NAD+)