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cell respiration

acetyl CoA

the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.


Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen

alcohol fermentation

The conversion of pyruvate to carbon dioxide and ethyl alcohol


Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.

ATP synthase

A cluster of several membrane proteins found in the mitochondrial crista (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. Provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion.

beta oxidation

A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.

cellular respiration

The most prevalent and efficient catabolic pathway for the production of ATP, in which oxygen is consumed as a reactant along with the organic fuel.


An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis.

citric acid cycle

A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing pyruvate to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; the second major stage in cellular respiration.


an iron-containing protein, a component of electron transport chains in mitochondria and chloroplasts

electron transport chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.

facultative anaerobe

an organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions


a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid


the splitting of glucose into puyruvate.

lactic acid fermentation

the conversion of puyruvate to lactate with no release of carbon dioxide


Nicotinamide adenine dinucleotide, a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism


the loss of electrons from a substance involved in a redox reaction

oxidative phosphorylation

the production of ATP using energy derived from the redox reaction of an electron transport chain

oxidizing agent

the electron acceptor in a redox reaction

proton-motive force

The potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis.

redox reaction

A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.

reducing agent

the electron donor in a redox reaction


the addition of electrons to a substance involved in a redox reaction

substrate-level phophorylation

the formation of ATP by directly transferring a phosphate group ADP from an intermediate substrate in catabolism

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