Metabolism, Energy

Metabolism

Sum of all chemical reactions that occur within a cell to obtain energy and synthesize cellular components.

Biochemical Pathway

Series of linked chemical reactions in which the product of one reaction becomes the substrate of the next.

Metabolite

Product of a biochemical reaction.

Intermediate

Metabolite formed between the initial reactant and the final product of a biochemical pathway.

Metabolite Flux

Rate at which metabolic intermediates are produced and consumed.

Catalyst

Substance that increases the rate of a chemical reaction without being permanently changed.

Substrate

Reactant upon which an enzyme acts.

Enzyme

Protein catalyst that lowers activation energy and increases the rate of a chemical reaction without changing reaction equilibrium.

Ribozyme

RNA molecule capable of catalytic activity.

Cofactor

Non-protein molecule required for enzyme activity.

Coenzyme

Organic cofactor that can dissociate from an enzyme after participating in a reaction.

Active Site

Specific region of an enzyme where substrates bind and the reaction occurs.

Induced Fit

Conformational change in an enzyme that occurs after substrate binding to facilitate catalysis.

Denaturation

Loss of an enzyme's three-dimensional structure resulting in loss of catalytic activity.

Competitive Inhibition

Enzyme inhibition in which an inhibitor competes with the substrate for the active site.

Sulfonamide

Antimicrobial that competitively inhibits bacterial folic acid synthesis by competing with PABA.

Microbial Metabolism

All chemical reactions that enable microorganisms to obtain energy, reducing power, and carbon skeletons.

Energy

Capacity to perform cellular work.

Catabolism

Metabolic process that breaks down molecules and conserves released energy as ATP.

Anabolism

Metabolic process that synthesizes cellular molecules using energy from ATP.

Adenosine Triphosphate (ATP)

Primary energy currency of the cell.

ATP Hydrolysis

Reaction in which ATP is converted to ADP and inorganic phosphate, releasing energy.

GTP

Nucleotide that functions as an energy carrier in certain cellular processes.

CTP

Nucleotide that functions as an energy carrier in specific biosynthetic reactions.

UTP

Nucleotide that functions as an energy carrier in carbohydrate metabolism.

Redox Reaction

Oxidation-reduction reaction involving the transfer of electrons.

Oxidation

Loss of electrons by a molecule.

Reduction

Gain of electrons by a molecule.

Electron Donor

Molecule that donates electrons and becomes oxidized.

Electron Acceptor

Molecule that accepts electrons and becomes reduced.

Standard Reduction Potential (E°')

Measure of a molecule's tendency to accept electrons.

Electron Transport Chain (ETC)

Series of membrane-bound electron carriers that transfer electrons through sequential redox reactions.

NAD⁺

Electron carrier that accepts electrons to form NADH.

NADH

Reduced electron carrier that donates electrons to the electron transport chain.

FADH₂

Reduced electron carrier that donates electrons to the electron transport chain.

Terminal Electron Acceptor

Final molecule that accepts electrons at the end of an electron transport chain.

Energy Source

Source from which a microorganism obtains energy.

Phototrophy

Process of obtaining energy from light.

Chemolithotrophy

Process of obtaining energy from oxidation of inorganic compounds.

Photolithoautotroph

Microorganism that uses light for energy, inorganic compounds for electrons, and carbon dioxide as its carbon source.

Photoorganoheterotroph

Microorganism that uses light for energy and organic compounds as both electron and carbon sources.

Chemolithoautotroph

Microorganism that uses inorganic compounds for energy and electrons and carbon dioxide as its carbon source.

Chemolithoheterotroph

Microorganism that uses inorganic compounds for energy and electrons but organic compounds as its carbon source.

Chemoorganoheterotroph

Microorganism that uses organic compounds as its energy, electron, and carbon source.

Photo-

Prefix indicating that light is used as the energy source.

Chemo-

Prefix indicating that chemical compounds are used as the energy source.

Litho-

Prefix indicating that inorganic compounds are used as the electron source.

Organo-

Prefix indicating that organic compounds are used as the electron source.

Auto-

Prefix indicating that carbon dioxide is used as the carbon source.

Hetero-

Prefix indicating that organic compounds are used as the carbon source.

Respiration

Metabolic process that oxidizes organic molecules to generate ATP through an electron transport chain.

Aerobic Respiration

Respiration in which oxygen serves as the terminal electron acceptor.

Anaerobic Respiration

Respiration in which a molecule other than oxygen serves as the terminal electron acceptor.

Glycolysis (Embden-Meyerhof Pathway)

Metabolic pathway that converts glucose into pyruvate while producing ATP and NADH.

Krebs Cycle (TCA Cycle)

Metabolic pathway that oxidizes acetyl-CoA to carbon dioxide while producing NADH, FADH₂, and GTP.

Acetyl-CoA

Molecule produced from pyruvate that enters the Krebs cycle.

Oxidative Phosphorylation

Process of ATP synthesis driven by the proton motive force generated by the electron transport chain.

Proton Motive Force (PMF)

Electrochemical gradient across a membrane that powers ATP synthesis, active transport, and flagellar rotation.

Fermentation

Energy-generating process that produces ATP through substrate-level phosphorylation without using an electron transport chain.

Substrate-Level Phosphorylation

ATP synthesis by direct transfer of a phosphate group from a phosphorylated intermediate to ADP.

Lactic Acid Fermentation

Fermentation pathway in which pyruvate is reduced to lactic acid to regenerate NAD⁺.

Alcoholic Fermentation

Fermentation pathway in which pyruvate is converted to ethanol and carbon dioxide to regenerate NAD⁺.

Photosynthesis

Process that converts light energy into chemical energy.

Photophosphorylation

ATP synthesis driven by light energy during photosynthesis.

Light Reactions

Photosynthetic reactions that use light energy to produce ATP, NADPH, and oxygen.

Dark Reactions (Calvin Cycle)

Photosynthetic reactions that use ATP and NADPH to fix carbon dioxide into glucose.

Oxygenic Photosynthesis

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

Anoxygenic Photosynthesis

Photosynthesis that uses inorganic compounds other than water as electron donors and does not release oxyg