The energy needed to make substrate molecules more reactive; enzymes function by lowering activation energy.
Adenosine triphosphate (ATP)
A nucleotide that is the primary form in which chemical energy is conserved and utilized in cells.
Allosteric enzyme
An enzyme that contains two combining sites, the active site (where the substrate binds) and the allosteric site (where an effector molecule binds).
Anabolic reactions (anabolism)
The biochemical processes involved in the synthesis of cell constituents from simpler molecules, usually requiring energy.
Anaerobic respiration
Use of an electron acceptor other than O2 in an electron transport–based oxidation leading to a proton motive force.
Aseptic technique
The manipulation of sterile instruments or culture media in such a way as to maintain sterility.
Autotroph
An organism able to grow on CO2 as sole source of carbon.
Catabolic reactions (catabolism)
The biochemical processes involved in the breakdown of organic or inorganic compounds, usually leading to the production of energy.
Catalyst
A substance that promotes a chemical reaction without itself being changed in the end.
Citric acid cycle
A cyclical series of reactions resulting in the conversion of acetate to CO2 and NADH. Also called the tricarboxylic acid cycle or Krebs cycle.
Coenzyme
A low-molecular-weight molecule that participates in an enzymatic reaction by accepting and donating electrons or functional groups. Examples: NAD+, FAD.
Complex medium
Any culture medium whose precise chemical composition is unknown. Also called undefined media.
Culture medium
An aqueous solution of various nutrients suitable for the growth of microorganisms.
Defined medium
Any culture medium whose exact chemical composition is known. Compare with complex medium.
Feedback inhibition
A decrease in the activity of the first enzyme of a biochemical pathway caused by buildup of the final product of the pathway.
Fermentation
Anaerobic catabolism of an organic compound in which the compound serves as both an electron donor and an electron acceptor and in which ATP is usually produced by substrate-level phosphorylation.
Glycolysis
Reactions of the Embden–Meyerhof–Parnas pathway in which glucose is converted to pyruvate.
Metabolism
All biochemical reactions in a cell, both anabolic and catabolic.
Pure culture
A culture containing a single kind of microorganism.