Chapter 8 - An Introduction to Metabolism Flashcards
metabolism
The totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.
metabolic pathway
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway).
catabolic pathway
A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules.
anabolic pathway
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules.
bioenergetics
(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.
energy
The capacity to cause change, especially to do work (to move matter against an opposing force).
kinetic energy
The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.
heat (thermal energy)
The total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal energy. Heat is energy in its most random form.
potential energy
The energy that matter possesses as a result of its location or spatial arrangement (structure).
chemical energy
Energy available in molecules for release in a chemical reaction; a form of potential energy.
thermodynamics
The study of energy transformations that occur in a collection of matter. (See first law of thermodynamics; second law of thermodynamics.)
first law of thermodynamics
The principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.
entropy
A measure of disorder, or randomness.
second law of thermodynamics
The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.
spontaneous process
A process that occurs without an overall input of energy; a process that is energetically favorable.
free energy
The portion of a biological system’s energy that can perform work when temperature and pressure are uniform throughout the system. The change in free energy of a system (ΔG) is calculated by the equation ΔG = ΔH - TΔS, where ΔH Is the change in enthalpy (in biological systems, equivalent to total energy), T is the absolute temperature, and ΔS is the change in entropy.
exergonic reaction
A spontaneous chemical reaction, in which there is a net release of free energy.
endergonic reaction
A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.
energy coupling
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
ATP (adenosine triphosphate)
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
phosphorylated intermediate
A molecule (often a reactant) with a phosphate group covalently bonded to it, making it more reactive (less stable) than the unphosphorylated molecule.
enzyme
A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.
catalyst
A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.
activation energy
The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.
substrate
The reactant on which an enzyme works.
enzyme-substrate complex
A temporary complex formed when an enzyme binds to its substrate molecule(s).
active site
The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.
induced fit
Caused by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate.
cofactor
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis.
coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.
competitive inhibitor
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics.
noncompetitive inhibitor
A substance that reduces the activity of an enzyme by binding to a location remove from the active site, changing the enzyme’s shape so that the active site no longer effectively catalyzes the conversion of substrate to product.
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.
cooperativity
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.
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.
