AP Biology Unit 3 A: Energy, Metabolism & Enzymes

Energy

the capacity to do work

Enzymes

proteins that act as biological catalysts

potential energy

stored energy that results from the position or shape of an object

chemical energy

A form of potential energy that is stored in chemical bonds between atoms.

kinetic energy

the energy an object has due to its motion

thermal energy

The total energy of motion in the particles of a substance

heat

thermal energy in transfer from one body of matter to another

light

a form of energy that travels in waves and can move through empty space where there is no air

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

second law of thermodynamics

when energy is changed from one form to another, some useful energy is always degraded into lower quality energy (usually heat) entropy

Law of Conservation of Energy

the law that states that energy cannot be created or destroyed but can be changed from one form to another

Gibbs free energy

the energy of a system that is available to do work at a constant temperature and pressure

Exergonic

Chemical reactions that release energy

Endergonic

A chemical reaction that requires the input of energy in order to proceed.

Metabolism

the combination of chemical reactions through which an organism builds up or breaks down materials

Catabolism

Metabolic pathways that break down molecules, releasing energy.

Anabolism

Metabolic pathways that construct molecules, requiring energy.

Catalytic proteins (enzymes)

speed up chemical reactions without being consumed themselves. work by decreasing the activation energy required.

energy of activation

The amount of energy that reactants must absorb before a chemical reaction will start

transition state

a high-energy intermediate state of the reactants during a chemical reaction that must be achieved for the reaction to proceed

globular proteins

spherical, water-soluble proteins.

induced-fit model

Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s)

enzyme-substrate complex

A temporary complex formed when an enzyme binds to its substrate molecule(s).

-ase

suffix of enzymes

cofactors and coenzymes

-non protein, small molecules that can bind to the active site of an enzyme and participate in catalyzing the reaction (use ionization, protonation, deprotonation)

-cofactors: usually inorganic molecules or metal ions

-coenzymes: small organic groups such as vitamins or NAD, FAD, CoA

competitive inhibition

substance that resembles the normal substrate competes with the substrate for the active site

noncompetitive inhibitors or allosteric regulators

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

allosteric

describes a region of an enzyme that can bind a regulatory molecule and is not the active site

feedback inhibition (negative feedback)

A metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway.

cooperativity & allosteric activation

A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits.