Lecture 11: Cellular Metabolism, Energetics, and Enzymes

Vocabulary flashcards defining fundamental concepts of cell energy, thermodynamics, ATP hydrolysis, enzyme activity, and metabolic control based on Lecture 11.

Metabolism

The totality of an organism's chemical reactions, which transforms matter and energy as an emergent property of life.

Metabolic Pathway

A series of chemical reactions that begins with a specific molecule and ends with 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, such as cellular respiration breaking down glucose in the presence of oxygen.

Anabolic Pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones, such as the synthesis of protein from amino acids.

Kinetic Energy

The form of energy associated with the motion of objects.

Heat (Thermal Energy)

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

Potential Energy

The energy that matter possesses because of its location or structure.

Chemical Energy

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 stating that the energy of the universe is constant; 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 (disorder) of the universe.

Spontaneous Process

A process that occurs without energy input, increases system stability, and has a negative change in free energy ($\Delta G < 0$).

Free Energy Change Equation

The mathematical relationship where $\Delta G = \Delta H - T\Delta S$, calculating the change in free energy ($\Delta G$) using enthalpy change ($\Delta H$), entropy change ($\Delta S$), and temperature in Kelvin ($T$).

Exergonic Reaction

A chemical reaction that proceeds with a net release of free energy and occurs spontaneously.

Endergonic Reaction

A chemical reaction that absorbs free energy from its surroundings and is nonspontaneous.

Energy Coupling

The use of an exergonic process to drive an endergonic one, managing energy resources to perform cellular work.

ATP (Adenosine Triphosphate)

The cell's energy shuttle composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups.

Phosphorylation

The transfer of a phosphate group from ATP to another molecule to drive endergonic reactions.

Phosphorylated Intermediate

A recipient molecule that has received a phosphate group transferred from ATP during an endergonic reaction.

Activation Energy ($E_A$)

The initial free energy required to break bonds and start a chemical reaction.

Catalyst

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

Enzyme

A catalytic protein that speeds up specific metabolic reactions by lowering the activation energy ($E_A$) barrier without affecting $\Delta G$.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active Site

The specific region on an enzyme where the substrate binds to undergo catalysis.

Induced Fit

The change in shape of an enzyme's active site upon binding a substrate to bring chemical groups into positions that enhance catalytic ability.

Cofactors

Nonprotein enzyme helpers that assist in catalytic activity, including inorganic metal ions such as $Fe^{2+}$ and $Mg^{2+}$.

Coenzyme

An organic cofactor required for enzyme activity, such as vitamins.

Competitive Inhibitors

Substances that reduce enzyme activity by directly binding to the active site, competing with the substrate.

Noncompetitive Inhibitors

Substances that bind to an enzyme's allosteric site, altering its shape so that the active site becomes less effective.

Allosteric Regulation

The process where a regulatory molecule binds to a protein at one site and affects the protein's function at a different site, stabilizing active or inactive forms.

Cooperativity

A form of allosteric regulation in which substrate binding to one active site in a multisubunit enzyme stabilizes favorable conformational changes at all other active sites.

Feedback Inhibition

A metabolic control mechanism in which the end product of a metabolic pathway binds to and inhibits an enzyme earlier in the pathway to halt production.