Energy and Enzymes in Biological Reactions

Energy

Capacity to do work or transfer heat.

Kinetic Energy

Energy in motion or being used.

Potential Energy

Stored energy not currently in use.

Thermodynamics

Study of energy transformations and interactions.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Entropy

Tendency of energy to disperse or spread out.

Second Law of Thermodynamics

Energy conversion is never 100% efficient.

Chemical Reactions

Processes that transform reactants into products.

Spontaneous Processes

Occur without constant energy input.

Chemical Energy

Potential energy in chemical bonds.

Enthalpy (∆H)

Total heat content of a system.

Enthalpy Change (∆H)

Energy flow during a reaction.

Gibbs Free Energy (G)

Energy available to do work.

ΔG

Change in Gibbs free energy.

Exergonic Reaction

Releases energy; -ΔG indicates spontaneity.

Endergonic Reaction

Absorbs energy; +ΔG indicates nonspontaneity.

ATP

Adenosine triphosphate; energy currency of cells.

Activation Energy (Ea)

Initial energy required to start a reaction.

Biological Catalysts

Substances that speed up reactions without heat.

Enzymes

Biological catalysts that lower activation energy.

Substrate

Reactant that binds to the enzyme's active site.

Enzyme Cofactors

Non-protein components required for enzyme activity.

Transition State

Intermediate state during a chemical reaction.

Factors Affecting Enzyme Function

pH, temperature, concentrations, and other molecules.

pH Optimum

Most enzymes function best near pH 7.

Temperature Effects

Reaction rates increase, but high temps denature proteins.

Substrate Concentration

Affects reaction rate; saturation leads to leveling off.

Metabolism

Collection of all chemical reactions in an organism.