Chapter 8 Flashcards

Metabolism

The sum of all chemical reactions in a cell that obtain and use energy to sustain life.

Coupled Reactions

Two linked reactions in which the energy released from one reaction is used to drive another reaction.

Catabolism

The breakdown of complex molecules into simpler molecules, releasing energy to produce ATP.

Anabolism

The building of complex molecules from simpler molecules using energy from ATP.

Exergonic Reaction

A chemical reaction that releases energy.

Endergonic Reaction

A chemical reaction that requires an input of energy.

Oxidation

The loss of electrons from a molecule, usually releasing energy.

Reduction

The gain of electrons by a molecule.

ATP (Adenosine Triphosphate)

The cell's main energy currency that stores and transfers energy for cellular work.

Enzyme

A protein catalyst that speeds up chemical reactions by lowering activation energy without being consumed.

Catalyst

A substance that speeds up a chemical reaction without being permanently changed.

Activation Energy

The minimum amount of energy needed to start a chemical reaction.

Reaction Rate

The speed at which reactants are converted into products.

Apoenzyme

The inactive protein portion of an enzyme that requires a cofactor or coenzyme to function.

Cofactor

A non-protein helper, usually a metal ion, required for enzyme activity.

Coenzyme

An organic helper molecule, often derived from vitamins, that assists enzyme function.

Holoenzyme

The complete, active enzyme consisting of an apoenzyme plus its cofactor or coenzyme.

Active Site

The region of an enzyme where the substrate binds and the reaction occurs.

Enzyme Specificity

The ability of an enzyme to bind only a specific substrate because of the shape of its active site.

Enzyme-Substrate Complex

The temporary complex formed when an enzyme binds its substrate before the reaction occurs.

Optimal Temperature

The temperature at which an enzyme functions at its highest activity.

Optimal pH

The pH at which an enzyme functions most efficiently.

Competitive Inhibitor

A molecule that competes with the substrate for the enzyme's active site.

Noncompetitive Inhibitor

A molecule that binds to a different site on the enzyme, changing its shape and reducing activity.

Feedback Inhibition

A form of regulation in which the final product of a metabolic pathway inhibits an earlier enzyme in the pathway.

Phosphorylation

The process of adding a phosphate group to ADP to produce ATP.

Substrate-Level Phosphorylation

ATP production by directly transferring a phosphate group from a substrate to ADP.

Oxidative Phosphorylation

ATP production using energy released by electrons moving through the electron transport chain.

Photophosphorylation

ATP production using energy from sunlight during photosynthesis.

Aerobic Cellular Respiration

The complete oxidation of glucose using oxygen as the final electron acceptor, producing 36–38 ATP.

Anaerobic Cellular Respiration

The complete oxidation of glucose using an electron acceptor other than oxygen, such as nitrate, sulfate, or carbonate.

Fermentation

The incomplete oxidation of glucose without an electron transport chain, producing only 2 ATP.

Electron Transport Chain (ETC)

A series of electron carriers that produce most of the ATP during cellular respiration.

Glycolysis

The first step of cellular respiration that breaks one glucose into two pyruvate molecules, producing a net of 2 ATP and 2 NADH.

Intermediate Step

The stage between glycolysis and the Krebs cycle where pyruvate is converted to acetyl-CoA.

Krebs Cycle (Citric Acid Cycle)

The second major stage of respiration that produces ATP, NADH, FADH₂, and carbon dioxide.

NADH

An electron carrier that transports high-energy electrons to the electron transport chain.

FADH₂

An electron carrier that delivers high-energy electrons to the electron transport chain.

Electron Acceptor

A molecule that receives electrons at the end of the electron transport chain.

Lactic Acid Fermentation

Fermentation that converts pyruvate into lactic acid while regenerating NAD⁺.

Alcohol Fermentation

Fermentation that converts pyruvate into ethanol and carbon dioxide while regenerating NAD⁺.

Mixed Acid Fermentation

Fermentation that produces a mixture of acidic end products.

Butanediol Fermentation

Fermentation that produces 2,3-butanediol as a major end product.

Deamination

Removal of an amino group from an amino acid so it can be used for energy.

Desulfurylation

Removal of sulfur from sulfur-containing amino acids.

Decarboxylation

Removal of a carboxyl group from an amino acid, releasing carbon dioxide.

Oxygenic Photosynthesis

Photosynthesis that uses water as the electron donor and produces oxygen.

Anoxygenic Photosynthesis

Photosynthesis that uses molecules other than water as the electron donor and does not produce oxygen.

Lithotroph

An organism that obtains electrons from inorganic compounds.

Organotroph

An organism that obtains electrons from organic compounds.

Autotroph

An organism that uses carbon dioxide as its carbon source.

Heterotroph

An organism that obtains carbon from organic compounds.