Metabolism and Bioenergetics Flashcards

These flashcards cover primary vocabulary and core concepts regarding metabolism, thermodynamics, ATP function, and enzyme regulation based on Chapter 6 lecture notes.

Metabolism

The totality of an organism’s chemical reactions; an emergent property of life arising from molecular interactions within the cell.

Metabolic pathway

A sequence of chemical reactions that begins with a specific molecule and ends with a product, where each step is catalyzed by a specific enzyme.

Catabolic pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds, such as in cellular respiration.

Anabolic pathways

Also called biosynthetic pathways, these consume energy to build complex molecules from simpler ones, such as synthesizing proteins from amino acids.

Bioenergetics

The study of how energy flows through living organisms.

Kinetic energy

Energy associated with the relative motion of objects.

Thermal energy

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

Heat

Thermal energy in transfer from one object to another.

Potential energy

Energy that matter possesses because of its location or structure.

Chemical energy

A term used by biologists to refer to the potential energy available for release in a chemical reaction.

Thermodynamics

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

First Law of Thermodynamics

The principle of conservation of energy: energy can be transferred and transformed, but it cannot be created or destroyed.

Second Law of Thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe.

Entropy

A measure of molecular disorder or randomness; it describes how dispersed energy is in a system.

Spontaneous processes

Processes that occur without energy input; for a process to occur in this manner, it must increase the entropy of the universe.

Free energy

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

$$\Delta G$$

The change in free energy, calculated as $G_{\text{final state}} - G_{\text{initial state}}$; only reactions with a negative value are spontaneous.

Exergonic reaction

A spontaneous chemical reaction that proceeds with a net release of free energy where $\Delta G$ is negative.

Endergonic reaction

A nonspontaneous chemical reaction that absorbs free energy from its surroundings where $\Delta G$ is positive.

Energy coupling

The use of an exergonic process to drive an endergonic one; most of this in cells is mediated by ATP.

ATP (adenosine triphosphate)

A molecule composed of ribose, adenine, and three phosphate groups; it is the cell's primary energy shuttle and is also used to make RNA.

Phosphorylation

The transfer of a phosphate group from ATP to another molecule, such as a reactant.

Phosphorylated intermediate

The recipient molecule with the phosphate group covalently bonded to it during phosphorylation, which is more reactive than the original unphosphorylated molecule.

Catalyst

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

Enzyme

A macromolecule (typically a protein) that acts as a catalyst to speed up metabolic reactions by lowering energy barriers.

Activation energy ($E_A$)

The initial investment of energy required to start a reaction by breaking bonds in the reactant molecules.

Substrate

The reactant molecule on which an enzyme acts.

Active site

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

Induced fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, caused by entry of the substrate.

Cofactors

Nonprotein molecules that help carry out processes difficult for amino acids; they can be inorganic (metal ions) or organic.

Coenzyme

An organic cofactor, such as a vitamin.

Competitive inhibitors

Substances that reduce the productivity of enzymes by blocking substrates from entering active sites.

Noncompetitive inhibitors

Substances that impede enzymatic reactions by binding to another part of the enzyme, causing the enzyme to change shape and rendering the active site less effective.

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.

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.