Introductory Biology: Energy and Enzymes

Vocabulary practice cards covering bioenergetics, thermodynamics, forms of energy, free energy, cellular respiration, and enzyme structure and inhibition.

Metabolism

All of the chemical reactions necessary to maintain life within an organism.

Catabolism

Metabolic reactions in which complex substances are broken down into simpler substances, releasing energy in the process.

Anabolism

Metabolic reactions in which larger, more complex molecules are built from smaller ones.

Cellular Respiration

The metabolic process in which glucose ($C_6H_{12}O_6$) is oxidized to yield carbon dioxide ($CO_2$), water ($H_2O$), and energy in the form of $\text{ATP}$.

Open System

A thermodynamic system that can freely exchange energy with its surroundings, such as a stovetop or biological organisms.

Closed System

A thermodynamic system that cannot exchange energy with its surroundings.

First Law of Thermodynamics

The law stating that energy can never be created or destroyed; it can only change from one form to another, remaining constant and conserved overall.

Second Law of Thermodynamics

The law stating that every conversion of energy includes the transformation of some energy into heat, which is mostly useless to living organisms.

Entropy

A scientific measure of randomness, disorder, or energy unavailability within a physical system.

Free Energy ($G$)

The Gibbs free energy in a system that is available to do work, tracked as total free-energy change (\text{\Delta}G) during chemical reactions.

Exergonic Reaction

A chemical reaction that proceeds with a net release of free energy (\text{\Delta}G < 0) and is spontaneous or energetically favorable.

Endergonic Reaction

A chemical reaction that absorbs free energy from its surroundings (\text{\Delta}G > 0) and is nonspontaneous.

Kinetic Energy

The energy possessed by a body due to its motion, including heat energy, light energy, moving electrons, and mechanical energy.

Potential Energy

The capacity to do work stored in a body as a result of its location, position, concentration gradient, or chemical structure.

Chemical Energy

A form of potential energy associated with the electronic structure of atoms and stored within chemical bonds.

$$\text{ATP}$$

Free-floating molecules in living cells that temporarily store potential energy in unstable chemical bonds to fuel vital cellular reactions.

Enzyme

A protein biological catalyst that accelerates chemical reactions by lowering their activation energy without being permanently altered or consumed.

Activation Energy

The initial energy input required for a chemical reaction to begin.

Substrate

The specific target molecule that an enzyme recognizes, binds to, and acts upon during a chemical reaction.

Active Site

The specific functional region on an enzyme where a substrate binds to form an enzyme–substrate complex.

Denaturation

The process by which a protein loses the three-dimensional functional shape that makes it active, usually caused by heat, extreme pH, or high salt concentrations.

Competitive Inhibitor

A molecule that prevents enzyme function by binding directly to the active site, competing with the natural substrate for access.

Noncompetitive Inhibitor

A molecule that prevents enzyme function by binding to a distant site on the enzyme, altering the active site's shape so the substrate cannot fit.

Acarbose

A specific competitive inhibitor of the enzyme $\alpha\text{-amylase}$ that functions to slow down the digestion of starch.