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Cells Harvest Chemical Energy
Chapter 6
18
Biology
Undergraduate 3
07/09/2008

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Term
redox reaction
Definition
short for oxidation-reduction; a chemical reaction in which electrons are lost from one substance (oxidation) and added to another (reduction). Oxidation and reduction always occur together.
Term
oxidation
Definition
the loss of electrons from a substance involved in a redox reaction; always accompanies reduction.
Term
reduction
Definition
the gain of electrons by a substance involved in a redox reaction; always accompanies oxidation.
Term
dehydrogenase
Definition
an enzyme that catalyzes a chemical reaction during which one or more hydrogen atoms are removed from a molecule.
Term
NAD+
Definition
Nicotinamide adenine dinucleotide; a coenzyme thaat assists enzymes by conveying electrons (from hydrogen atoms) during the redox reactions of cellular metabolism. The plus sign indicates that the molecule is oxidized and ready to pick up hydrogens; the reduced, hydrogen (electron)-carrying form is NADH.
Term
electron transport chain
Definition
a series of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP; located in the inner membrane of mitochondria, the thylakoid memebranes of chloroplasts, and the plasma membranes of prokaryotes.
Term
glycolysis
Definition
the multistep chemical breakdown of a molecules of glucose into two molecules of pyruvate; the first stage of cellular respiration in all organisms; occurs in the cytoplasmic fluid.
Term
citric acid cycle
Definition
the metabolic cycle fueled by acetyl CoA formed after glycolysis in cellular respiration. Chemical reactions in the citric acid cycle complete the metabolic breakdown of glucose molecules to carbon dioxide. The cycle occurs in the matrix of mitochondria and supplies most of the NADH molecules that carry energy to the electron transport chains.
Term
oxidative phosphorylation
Definition
The production of ATP using energy derived from the redox reactions of an electron transport chain.
Term
chemiosmosis
Definition
The production of ATP using the energy of hydrogen ion (H+) gradients across membranes to phosphorylate ADP; powers most ATP synthesis in cells.
Term
ATP synthases
Definition
A complex (cluster) of several proteins found in a cellular membrane (including the inner membrane of mitochondria, the thylakoid membrane of chloroplasts, and the plasma membrane of prokaryotes) that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. An ATP synthase provides a port through which hydrogen ions (H+) diffuse.
Term
substrate-level phosphorylation
Definition
The formation of ATP occuring when an enzyme transfers a phosphate group from an organic molecule (e.g., one of the intermediates in glycolysis or the citric acid cycle) to ADP.
Term
intermediate
Definition
One of the compounds that form between the initial reactant and the final product in a metabolic pathway, such as between glucose and pyruvate in glycolysis.
Term
acetyl CoA (acetyl coenzyme A)
Definition

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

Term
lactic acid fermentation
Definition
The conversion of pyruvate to lactate with no release of carbon dioxide.
Term
alcohol fermentation
Definition
The conversion of the acid produced by glycolysis to carbon dioxide and ethyl alcohol.
Term
strict anaerobe
Definition
An organism that cannot survive in an atmosphere of oxygen.
Term
facultative anaerobe
Definition
A microorganism that makes ATP by aerobic respiration if oxygen is present, but that switches to fermentation when oxygen is absent.
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