Anatomy & Physiology: Energy, Chemical Reactions, and Cellular Respiration

Comprehensive vocabulary flashcards covering energy types, laws of thermodynamics, chemical reaction classes, and enzyme kinetics, structures, and regulation.

Energy

The capacity to do work.

Potential energy

The energy of position or stored energy.

Kinetic energy

The energy of motion.

Chemical energy

A form of potential energy stored in a molecule's chemical bonds that is released when bonds are broken.

Electrical energy

A form of kinetic energy involving the movement of charged particles, such as ions moving across a plasma membrane.

Mechanical energy

A form of kinetic energy exhibited by objects in motion due to an applied force.

Sound energy

A form of kinetic energy caused by a vibrating object compressing molecules.

Radiant energy

The energy of electromagnetic waves, such as visible light.

Heat

The kinetic energy derived from the random movement of atoms, ions, or molecules, measured as temperature.

Thermodynamics

The study of energy transformations.

First law of thermodynamics

The law stating that energy can neither be created nor destroyed, but can only change in form.

Second law of thermodynamics

The law stating that when energy is transformed, some energy is lost to heat, decreasing the amount of usable energy.

Metabolism

The collective term for all biochemical reactions occurring in living organisms.

Reactants

Substances present prior to the start of a chemical reaction, written on the left side of a chemical equation.

Products

Substances formed by a chemical reaction, written on the right side of a chemical equation.

Decomposition reaction

A chemical reaction in which an initial large molecule is broken down into smaller structures ($AB \rightarrow A + B$).

Catabolism

The collective term for all decomposition reactions in the body.

Synthesis reaction

A chemical reaction in which two or more structures combine to form a larger structure ($A + B \rightarrow AB$).

Anabolism

The collective term for all synthesis reactions in the body.

Exchange reaction

A chemical reaction involving both decomposition and synthesis components where groups are exchanged between structures ($AB + C \rightarrow A + BC$).

Oxidation-reduction reaction (redox reaction)

An exchange reaction where electrons are moved from one chemical structure to another.

Oxidation

The process in a redox reaction where a chemical structure loses an electron.

Reduction

The process in a redox reaction where a chemical structure gains an electron.

Exergonic reactions

Chemical reactions in which reactants have more energy in their bonds than products, resulting in a net release of energy.

Endergonic reactions

Chemical reactions in which reactants have less energy in their bonds than products, requiring net energy input.

ATP cycling

The continuous formation and breakdown of ATP in cells.

Irreversible reaction

A chemical reaction that results in a net loss of reactants and a net gain in products.

Reversible reaction

A chemical reaction that proceeds in both directions until equilibrium is established with no net change in concentrations.

Reaction rate

A measure of how quickly a chemical reaction takes place.

Activation energy ($E_a$)

The energy required to break existing chemical bonds to initiate a reaction.

Enzymes

Biologically active protein catalysts that accelerate chemical reactions by decreasing activation energy.

Active site

The unique three-dimensional region on an enzyme protein chain where a specific substrate binds.

Induced fit model

The model of enzyme catalysis where an enzyme changes shape slightly upon substrate binding to achieve a closer fit.

Cofactors

Nonprotein organic or inorganic helper substances required to ensure an enzymatic reaction occurs.

Coenzymes

Organic cofactors, such as vitamins or modified nucleotides, that assist enzyme function.

Oxidoreductases

A functional class of enzymes that catalyze oxidation-reduction reactions.

Transferases

A functional class of enzymes that transfer functional groups, atoms, or molecules between chemical structures.

Hydrolases

A functional class of enzymes that split chemical bonds using water.

Isomerases

A functional class of enzymes that convert one isomer into another.

Ligases

A functional class of enzymes that bond two molecules together.

Lyases

A functional class of enzymes that split chemical bonds without using water.

Saturation

The state in an enzyme-catalyzed reaction where substrate concentration is so high that all enzyme molecules are engaged.

Optimal temperature

The temperature at which human enzymes function best, usually $40^\circ\text{C}$ ($104^\circ\text{F}$).

Competitive inhibitor

A substance that structurally resembles the substrate and competes for binding at the enzyme's active site.

Noncompetitive inhibitor

A substance that binds to an enzyme at an allosteric site, inducing a conformational change that inactivates the enzyme.

Metabolic pathway

A series of enzymes where the product of one enzyme becomes the substrate for the next enzyme in the sequence.

Multienzyme complex

A group of physically attached enzymes that work sequentially to carry out a reaction series.

Negative feedback

A regulatory mechanism where the end product of a metabolic pathway acts as an allosteric inhibitor to turn off an enzyme early in the pathway.

Phosphorylation

The addition of a phosphate group to an enzyme by phosphorylases or kinases.

Dephosphorylation

The removal of a phosphate group from an enzyme by phosphatases.

Lactase

An enzyme embedded in small intestine cell walls that breaks lactose down into glucose and galactose.