Chapter 8: An Introduction to Metabolism

Flashcards to help you review key concepts in the chapter, including energy laws, metabolic pathways, enzymes, and regulation.

Define bioluminescence.

The conversion of energy stored in organic molecules to light.

State the first law of thermodynamics.

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

State the second law of thermodynamics.

Every energy transfer or transformation increases the entropy (disorder) of the universe.

Define energy.

The capacity to cause change; the ability to rearrange a collection of matter.

Define kinetic energy.

Energy associated with the relative motion of objects.

Define thermal energy.

Kinetic energy associated with the random movement of atoms or molecules.

Define heat.

Thermal energy in transfer from one object to another.

Define potential energy.

Energy that matter possesses because of its location or structure.

Define chemical energy.

Potential energy available for release in a chemical reaction.

Define metabolism.

The totality of an organism’s chemical reactions, arising from orderly interactions between molecules.

Define metabolic pathway.

A series of defined steps in which a specific molecule is altered, resulting in a certain product, with each step catalyzed by a specific enzyme.

Define catabolic pathways.

Metabolic pathways that release energy by breaking down complex molecules to simpler compounds (breakdown pathways).

Define anabolic pathways.

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

Define thermodynamics.

The study of the energy transformations that occur in a collection of matter.

Define system in thermodynamics.

The matter under study.

Define open system.

A system in which energy and matter can be transferred between the system and its surroundings.

Define spontaneous process.

A process that leads to an increase in entropy and can proceed without requiring an input of energy; energetically favorable.

Define nonspontaneous process.

A process that leads to a decrease in entropy and will happen only if energy is supplied.

Define entropy.

A measure of molecular disorder, or randomness.

Define Gibbs free energy.

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

Define exergonic reaction.

A reaction that proceeds with a net release of free energy; DG is negative.

Define endergonic reaction.

A reaction that absorbs free energy from its surroundings; DG is positive.

Define energy coupling.

The use of an exergonic process to drive an endergonic one.

Define phosphorylated intermediate.

A molecule with a phosphate group covalently bonded to it, making it more reactive (less stable, with more free energy).

Define catalyst.

A chemical agent that speeds up a reaction without being consumed by the reaction.

Define enzyme.

A macromolecule, typically a protein, that acts as a catalyst, speeding up a reaction without being consumed by the reaction.

Define activation energy (EA).

The initial investment of energy for starting a reaction; the energy required to contort the reactant molecules so bonds can break.

Define substrate.

The reactant an enzyme acts on.

Define active site.

A pocket or groove on the surface of the enzyme where catalysis occurs.

Define induced fit.

The tightening of the binding after initial contact, where the enzyme changes shape slightly due to interactions between the substrate's chemical groups and chemical groups on the side chains of the amino acids that form the active site.

Define cofactors.

Nonprotein helpers required by many enzymes for catalytic activity, often for chemical processes like electron transfers.

Define coenzyme.

An organic molecule serving as a cofactor.

Define competitive inhibitors.

Reversible inhibitors that resemble the normal substrate molecule and compete for admission into the active site, reducing the productivity of enzymes by blocking substrates from entering active sites.

Define noncompetitive inhibitors.

Inhibitors that impede enzymatic reactions by binding to another part of the enzyme, causing the enzyme molecule to change its shape in such a way that the active site becomes much less effective at catalyzing the conversion of substrate to product.

Define allosteric regulation.

The term used to describe any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site; may result in either inhibition or stimulation of an enzyme’s activity.

Define cooperativity.

A mechanism amplifying the response of enzymes to substrates; one substrate molecule primes an enzyme to act on additional substrate molecules more readily.

Define feedback inhibition.

A common mode of metabolic control in which a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.