Chapter 06: Energy and Metabolism

Vocabulary flashcards defining key energy, thermodynamics, and enzymatic terms from Chapter 06.

Thermodynamics

The branch of chemistry concerned with energy changes in physical and chemical processes.

Kinetic Energy

The energy of motion.

Potential Energy

Stored energy that results from an object's position, location, or chemical structure.

Calorie

The heat required to raise the temperature of $1\,g$ of water by $1^\circ\text{C}$.

Oxidation

A chemical process in which an atom or molecule loses an electron.

Reduction

A chemical process in which an atom or molecule gains an electron, resulting in a higher energy level than its oxidized form.

First Law of Thermodynamics

The physical law stating that energy cannot be created or destroyed, only changed from one form to another, keeping the total amount of energy in the universe constant.

Second Law of Thermodynamics

The physical law stating that entropy (disorder) is continuously increasing and energy transformations proceed spontaneously to convert matter into a less ordered form.

Entropy

A measure of disorder or randomness in a system, represented by the variable $S$.

Enthalpy

The total energy contained in a molecule's chemical bonds, represented by the variable $H$.

Free Energy

The energy available to do work in a system, defined mathematically by $G = H - TS$.

Endergonic Reaction

A chemical reaction with a positive change in free energy ($\Delta G > 0$) that requires an input of energy and is non-spontaneous.

Exergonic Reaction

A chemical reaction with a negative change in free energy ($\Delta G < 0$) that releases energy and occurs spontaneously.

Activation Energy

The extra energy required to destabilize existing chemical bonds and initiate a chemical reaction.

Catalyst

A substance that lowers the activation energy of a chemical reaction to increase its rate without altering the proportion of reactants turned into products.

Adenosine Triphosphate (ATP)

The primary energy currency used by cells, composed of ribose, adenine, and a chain of three phosphate groups.

Enzyme

A biological catalyst, usually a protein or RNA molecule, that speeds up specific chemical reactions without being changed or consumed.

Active Site

The specific pocket or cleft on an enzyme where substrate molecules bind to form an enzyme-substrate complex.

Induced Fit

The alteration of an enzyme's shape upon substrate binding to apply stress to specific chemical bonds and lower activation energy.

Multienzyme Complex

An assembly of multiple enzymes physically attached together that carries out a sequence of reactions efficiently without unwanted side reactions.

Ribozyme

An RNA molecule that functions as a nonprotein biological catalyst.

Competitive Inhibitor

An inhibitor that competes directly with the substrate for binding at the active site of an enzyme.

Noncompetitive Inhibitor

An inhibitor that binds to an enzyme at a site other than the active site, altering the enzyme's shape so it cannot bind its substrate.

Allosteric Site

A specific binding site on an enzyme distinct from the active site that acts as a chemical on/off switch for enzyme activity.

Allosteric Inhibitor

A substance that binds to an allosteric site and reduces enzyme activity.

Allosteric Activator

A substance that binds to an allosteric site and increases enzyme activity.

Cofactor

A nonprotein helper, often an inorganic metal ion such as zinc, molybdenum, or manganese, that assists enzyme function.

Coenzyme

A nonprotein organic cofactor, such as a vitamin, that assists an enzyme in catalysis.

Metabolism

The sum total of all chemical reactions carried out by an organism.

Anabolism

Metabolic reactions that expend energy to build complex molecules from simpler ones.

Catabolism

Metabolic reactions that harvest energy by breaking down complex molecules into simpler ones.

Biochemical Pathway

A sequence of chemical reactions in a cell where the product of one reaction becomes the substrate for the next.

Feedback Inhibition

A regulatory mechanism where the end-product of a biochemical pathway binds to an allosteric site on an enzyme early in the pathway to shut down further production.