Metabolism and Enzymes - AP Biology Unit 3: Energetics

Vocabulary flashcards covering key concepts of metabolism and enzymes from the notes.

Metabolism

The totality of an organism's chemical reactions; an emergent property arising from interactions among molecules in the cell.

Catabolic pathway

A pathway that releases energy by breaking down complex molecules into simpler ones (e.g., cellular respiration).

Anabolic pathway

A pathway that consumes energy to build complex molecules from simpler ones (e.g., protein synthesis).

Bioenergetics

The study of how organisms manage their energy resources.

Biochemical pathway

A series of enzymatic activities that maintain cellular homeostasis; each enzyme typically catalyzes one step.

Exergonic reaction

Releases free energy and proceeds spontaneously; AG is negative.

Endergonic reaction

Absorbs free energy and is nonspontaneous; AG is positive.

Free energy change (AG)

The difference in free energy between final and initial states; negative AG indicates a spontaneous process.

Energy coupling

Using an exergonic process to drive an endergonic one, often via ATP.

ATP (adenosine triphosphate)

The energy currency of the cell: adenine, ribose, and three phosphate groups; used to drive cellular work and RNA synthesis.

ATP hydrolysis

Breakdown of ATP to ADP and inorganic phosphate, releasing energy.

Activation energy

The energy barrier that must be overcome for a reaction to proceed; lowered by enzymes.

Enzyme

A biological catalyst, usually a protein, that speeds up a chemical reaction without being consumed.

Substrate

The reactant that binds to an enzyme's active site.

Active site

The region of the enzyme where the substrate binds.

Enzyme–substrate complex

The temporary complex formed when a substrate binds to its enzyme.

Induced fit

Enzyme changes shape to better accommodate the substrate, enhancing catalysis.

Cofactor

A nonprotein helper required by some enzymes; can be inorganic.

Coenzyme

An organic helper (often vitamins) that assists enzyme activity.

Competitive inhibitor

A molecule that competes with the substrate for binding at the enzyme’s active site.

Noncompetitive inhibitor

A molecule that binds elsewhere on the enzyme, causing a shape change and reduced activity.

Allosteric regulation

Regulation of an enzyme by binding to a site other than the active site, which can activate or inhibit.

Allosteric activator

A regulator that binds to an allosteric site and stabilizes the enzyme’s active form.

Allosteric inhibitor

A regulator that binds to an allosteric site and stabilizes the inactive form.

Cooperativity

A form of allosteric regulation where one substrate molecule increases enzyme activity at other sites.

Feedback inhibition

The end product inhibits an earlier enzyme in the pathway to regulate production.

Denaturation

Loss of protein structure and function due to factors like high temperature or extreme pH.

Localization of enzymes

Enzymes are organized in specific organelles or structures to coordinate pathways (e.g., respiration in mitochondria).

Mitochondria

Organelles where stages of cellular respiration occur; contain enzymes in the matrix and inner membrane.

Three kinds of cellular work

Mechanical, transport, and chemical work powered by ATP.

First Law of Thermodynamics

Energy cannot be created or destroyed; it can be transferred or transformed; total energy of the universe is constant.

Second Law of Thermodynamics

Every energy transfer increases the entropy of the universe; some energy is lost as heat.

Entropy

A measure of disorder or randomness; tends to increase in energy transformations.

Open system

A system that exchanges energy and matter with its surroundings; organisms are open systems.

Equilibrium

A state where forward and reverse reactions occur at the same rate; maximum stability; living cells are not at equilibrium.

Forms of energy

Kinetic (motion), Potential (stored), Thermal (random motion), and other usable forms of energy.

Heat

Thermal energy in transfer between objects.

Vmax

The maximum rate of an enzyme-catalyzed reaction when the enzyme is saturated with substrate.

Optimal temperature/pH

Each enzyme has a specific temperature and pH at which it functions best.

Cofactors and vitamins

Cofactors can be inorganic; organic cofactors are coenzymes and include vitamins.

Enzyme specificity

Enzymes are highly specific for their substrates due to the fit of the active site.