BIO 202 - LEC 4

Vocabulary flashcards covering cellular metabolism, thermodynamics, ATP hydrolysis, enzyme activation energy, Michaelis-Menten kinetics, and enzyme regulation mechanisms from Chapter 8.

Metabolism

The totality of an organism's chemical reactions, arising as an emergent property from orderly molecular interactions.

Metabolic Pathway

A series of steps in which a specific molecule is altered to produce a product, with 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 complex molecules from simpler ones.

Kinetic Energy

Energy associated with motion.

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

Potential energy available for release in a chemical reaction.

Isolated System

A system that is unable to exchange energy or matter with its surroundings.

Open System

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

First Law of Thermodynamics

The principle stating that energy can be transferred and transformed, but it cannot be created or destroyed; the energy of the universe is constant.

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.

Gibbs Free Energy ($G$)

A measure of a system's stability, where unstable systems (higher $G$) tend to become more stable (lower $G$).

Exergonic Reaction

A spontaneous chemical reaction with a net release of free energy (\text{\Delta} G < 0) where products store less free energy than reactants.

Endergonic Reaction

A nonspontaneous chemical reaction that absorbs free energy from its surroundings (\text{\Delta} G > 0) where products store more free energy than reactants.

Exergonic vs. Endergonic Reaction Profiles

Graphs depicting free-energy changes, showing that exergonic reactions release free energy (\text{\Delta} G < 0) and endergonic reactions absorb free energy (\text{\Delta} G > 0).

Energy Coupling

The use of an exergonic process to drive an endergonic one, mediated in cells primarily by ATP.

ATP (Adenosine Triphosphate)

A molecule composed of ribose, adenine, and three phosphate groups that mediates most energy coupling in cells and functions as a nucleoside triphosphate used to make RNA.

Phosphorylation

The transfer of a phosphate group from ATP to another molecule, typically used to power endergonic reactions.

Phosphorylated Intermediate

A recipient molecule that receives a phosphate group from ATP, making it more reactive (less stable, with higher free energy) than the original molecule.

Catalyst

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

Enzyme

A macromolecule (typically protein) that acts as a catalyst to speed up a specific reaction.

Activation Energy ($E_A$)

The initial investment of energy required to contort reactant molecules into an unstable state so that bonds can break.

Transition State

The highly unstable state reached when reactant molecules absorb enough energy for their bonds to break.

Substrate

The specific reactant that an enzyme acts on.

Active Site

The specific region on an enzyme, often a pocket or groove, that binds to the substrate.

Induced Fit

The slight change in shape of an enzyme's active site upon binding a substrate, bringing active site chemical groups into positions that enhance catalysis.

$$V_{\text{max}}$$

Maximum velocity; the highest reaction rate achieved when essentially all enzyme active sites are occupied by substrate.

$$K_M$$

The substrate concentration required for an enzyme to reach half of its maximum velocity ($V_{\text{max}}$).

Cofactors

Nonprotein enzyme helpers that can associate loosely or tightly with an enzyme, including inorganic metal ions such as $\text{Zn}^{2+}$, $\text{Fe}^{2+}/\text{Fe}^{3+}$, and $\text{Cu}^{2+}$.

Coenzymes

Organic cofactors, most of which either act as vitamins or provide raw materials to make them.

Competitive Inhibitors

Inhibitors that resemble the substrate and bind to the active site of an enzyme, blocking substrate access and reducing enzyme productivity.

Noncompetitive Inhibitors

Inhibitors that bind away from the active site, inducing a shape change in the enzyme that makes the active site less effective.

Allosteric Regulation

Regulation where an activating or inhibiting molecule binds to a regulatory site (often located where subunits join), stabilizing either the active or inactive form of the enzyme.

Cooperativity

A form of allosteric activation where substrate binding to one active site triggers a shape change in the enzyme that affects the active form for all other sites.

Positive Cooperativity

When binding of a substrate to one active site increases the affinity of remaining active sites for subsequent substrates.

Negative Cooperativity

When binding of a substrate to one active site decreases the affinity of remaining active sites for subsequent substrates.

Feedback Inhibition

A metabolic control method in which the end product of a metabolic pathway inhibits an enzyme acting earlier in the pathway, preventing the cell from wasting chemical resources.