Cellular Energetics Quiz 3.1 & 3.2

Free Energy

(G) depends on the energy available to do work & the disorderedness (entropy) of the system

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Systems trend from order to disorder.

Entropy

disorderedness/randomness

Metabolism

the sum of all chemical reactions that occur in living organisms to sustain life

Exergonic Reaction

Reactions that release energy (-ΔG); they reduce the usable free energy in the system

Endergonic Reaction

Reactions that require energy (+ΔG); they increase the usable free energy in the system

Activation energy

the amount of energy required for a reaction to proceed

Enzyme

biological catalysts that decrease the activation energy of a reaction (but do not alter ΔG)

Active Site

region of the enzyme where a substrate molecule binds and undergoes a chemical reaction

Substrate

a molecule that an enzyme acts upon during a biochemical reaction

Lock and Key Model

illustrates that the active site has a shape that only allows the substrate to fit

Induced Fit Model

describes a small conformational change that occurs when substrate binds active site; more accurate model

Conformation

shape of something

Cofactor

inorganic molecules (like metals or ions) that help enzymes function

Coenzyme

carbon-based molecules that help enzymes function

Denaturation

unfolding of a protein; loss of biological function

Renaturation

refolding of a protein; regain biological activity

Enzyme saturation

enzymes are fully occupied = maximum rate of reaction

Inhibitor

molecules that block enzyme function

Reversible Inhibition

inhibitor can be removed from the enzyme

Irreversible Inhibition

inhibitor cannot be removed from the enzyme (covalently bound)

Competitive Inhibition

Molecule “competes” directly with substrate; fits in active site

Non-competitive/allosteric inhibition

Molecule binds to the enzyme NOT in the active site

Allosteric site

site on the enzyme where allosteric inhibitors bind to the enzyme and cause a shape change