Chapter 03: Energy, Chemical Reactions, and Cellular Respiration

Vocabulary practice flashcards generated from Chapter 3 on energy, chemical reactions, enzymes, and cellular respiration.

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.

First law of thermodynamics

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

Second law of thermodynamics

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

Metabolism

The collective term for all biochemical reactions in living organisms.

Decomposition reaction

A chemical reaction in which an initial large molecule is broken down into smaller chemical structures ($AB \rightarrow A + B$). All such reactions in the body are referred to as catabolism.

Synthesis reaction

A chemical reaction in which two or more chemical structures combine to form a larger structure ($A + B \rightarrow AB$). All such reactions in the body are referred to as anabolism.

Exchange reaction

A chemical reaction in which groups are exchanged between two chemical structures, containing both decomposition and synthesis components ($AB + C \rightarrow A + BC$).

Oxidation-reduction reaction

An exchange reaction in which electrons are moved from one chemical structure to another; also known as a redox reaction.

Oxidized

Refers to a chemical structure that loses an electron during an oxidation-reduction reaction.

Reduced

Refers to a chemical structure that gains an electron during an oxidation-reduction reaction.

Exergonic reaction

A chemical reaction in which reactants have more potential energy in their bonds than the products, resulting in a net release of energy.

Endergonic reaction

A chemical reaction in which reactants have less energy in their chemical bonds than the products, requiring a net input of energy.

Activation energy

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

Enzymes

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

Active site

A unique three-dimensional region on an enzyme where a specific substrate temporarily binds to form an enzyme-substrate complex.

Induced fit model

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

Coenzymes

Organic nonprotein cofactors, such as vitamins or modified nucleotides, that assist enzymes in functioning.

Enzyme saturation

The condition occurring when substrate concentration is so high that all active sites of enzyme molecules are continuously bound to substrate.

Competitive inhibitor

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

Noncompetitive inhibitor

An inhibitor that binds to an allosteric site rather than the active site, inducing a conformational change that prevents the substrate from binding.

Phosphorylation

The addition of a phosphate group to a molecule, performed by enzymes called phosphorylases or kinases.

Dephosphorylation

The removal of a phosphate group from a molecule, catalyzed by enzymes known as phosphatases.

Cellular respiration

An exergonic multistep metabolic pathway in which organic molecules are oxidized to synthesize ATP.

Substrate-level phosphorylation

The direct transfer of a phosphate group from a substrate to ADP to form ATP during metabolic reactions.

Oxidative phosphorylation

The indirect formation of ATP where energy is first transferred to coenzymes ($NADH$, $FADH_2$) and then used in the electron transport system to synthesize ATP.

Glycolysis

An anaerobic metabolic pathway in the cytosol involving ten steps that breaks down one glucose molecule into two pyruvate molecules, producing a net yield of $2\,ATP$ and $2\,NADH$.

Intermediate stage

An aerobic process in the mitochondrial matrix catalyzed by pyruvate dehydrogenase that converts pyruvate and coenzyme A into acetyl $CoA$, generating $1\,NADH$ and releasing $1\,CO_2$ per pyruvate.

Citric acid cycle

A cyclic metabolic pathway located in the mitochondrial matrix consisting of nine enzymes that converts acetyl $CoA$ to $2\,CO_2$, yielding $1\,ATP$, $3\,NADH$, and $1\,FADH_2$ per turn.

Electron transport system

A series of $H^+$ pumps and electron carriers embedded in the mitochondrial cristae that uses energy from electrons to generate a proton gradient used by ATP synthase to form ATP.

Beta oxidation

An enzymatic process that breaks down fatty acids two carbons at a time to form acetyl $CoA$, which can then enter the citric acid cycle aerobically.