Dr. D Chpt. 8

Metabolism

The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways.

Metabolic Pathway

A series of chemical reactions that begins with a specific substrate and ends with a product, each step catalyzed by a specific enzyme.

Catabolic Pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds.

Anabolic Pathways

Metabolic pathways that consume energy to build complicated molecules from simpler ones.

Kinetic Energy

Energy associated with the relative motion of objects.

Thermal Energy

Kinetic energy associated with the random movement of atoms or molecules; transferred as heat.

Potential Energy

Energy that matter possesses because of its location or structure.

Chemical Energy

Potential energy available for release in a chemical reaction due to molecular structure.

First Law of Thermodynamics

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

Second Law of Thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

Entropy

A measure of molecular disorder or randomness within a system (symbolized as S).

Open System

A thermodynamic system where energy and matter can be transferred between the system and its surroundings (e.g., living organisms).

Gibbs Free Energy (G)

The portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system.

Delta G Equation

Delta G = Delta H - T*(Delta S)

Delta H (Enthalpy)

The change in total energy/heat of a system; negative if exothermic, positive if endothermic.

Spontaneous Process

A process that occurs without energy input, resulting in a negative Delta G.

Exergonic Reaction

A spontaneous chemical reaction with a net release of free energy (Delta G is negative).

Endergonic Reaction

A non-spontaneous chemical reaction that absorbs free energy from its surroundings (Delta G is positive).

ATP (Adenosine Triphosphate)

An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed; powers cellular work.

Components of ATP

Adenine (nitrogenous base), Ribose (5-carbon sugar), and 3 Phosphate groups.

Energy Coupling

The use of an exergonic process (like ATP hydrolysis) to drive an endergonic process.

Phosphorylated Intermediate

A molecule with a phosphate group covalently attached to it (from ATP), making it more reactive and less stable.

Inorganic Phosphate (Pi)

A free phosphate group (PO4 3-) released during ATP hydrolysis, no longer bound to an organic molecule.

Enzyme

A macromolecule (usually a protein) that serves as a biological catalyst to speed up chemical reactions.

Activation Energy (Ea)

The initial amount of energy needed to push reactants over an energy barrier to reach the transition state.

Substrate

The specific reactant on which an enzyme acts.

Active Site

The specific region on an enzyme where the substrate binds and catalysis occurs.

Induced Fit

The change in shape of an enzyme's active site so that it binds more snugly to the substrate upon binding.

Co-factors

Non-protein helpers required for proper enzyme activity; can be inorganic (metal ions) or organic (co-enzymes).

Co-enzymes

Organic co-factors, predominantly vitamins or derived from vitamins.

Competitive Inhibitor

A substance that reduces enzyme activity by entering the active site in place of the substrate, mimicking its structure.

Non-competitive Inhibitor

A substance that reduces enzyme activity by binding to an allosteric site, changing the enzyme's shape and active site accessibility.

Allosteric Regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

Feedback Inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.