Encyclopedia of Chemistry

chemiluminescence Spontaneous light emission cre-
ated by the chemical (enzymatic) conversion of a non-
light-emitting substrate.

chemiosmosis A method of making ATPthat uses the
ELECTRON-TRANSPORT CHAINand a PROTON PUMPto
transfer hydrogen protons across certain membranes
and then utilize the energy created to add a phosphate
group (phosphorylate) to adenosine diphosphate
(ADP), creating ATP as the end product.

chemistry The science that studies matter and all its
transformations.

chemoautotroph(chemolithotroph) An organism
that uses carbon dioxide as its carbon source and
obtains energy by oxidizing inorganic substances.

chemoheterotroph Any organism that derives its

energy by oxidizing organic substances for both carbon

source and energy.

chemoreceptor A sense organ, cell, or structure

that detects and responds to chemicals in the air or in

solution.

chemoselectivity, chemoselective Chemoselectiv-

ity is the preferential reaction of a chemical reagent

with one of two or more different functional groups.

A reagent has a high chemoselectivity if reaction

occurs with only a limited number of different func-

tional groups. For example, sodium tetrahydroborate

is a more chemoselective reducing agent than is

lithium tetrahydroaluminate. The concept has not

been defined in more quantitative terms. The term is

also applied to reacting molecules or intermediates

chemoselectivity, chemoselective 49

Assorted chemical weights. The different amount of each chemical represents a measurement known as the mole. One mole of any sam-
ple contains the same number of molecules or atoms. The weight (shown in grams) of each molar sample is determined by the weight of
the molecules (the molecular weight) and is calculated from the weights of the atoms in the molecule. Three of the chemicals are
hydrated with water (H 2 O). The chemical formulae are, clockwise from lower left: NaCl, FeCl 3 ·6(H 2 O), CuSO 4 ·5(H 2 O), KI, Co(NO 3 ) 2 ·6(H 2 O),
and KMnO 4. The heaviest atom here is iodine (I), eight times heavier than oxygen (O). The transition-metal compounds are colored.
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