model A synthetic COORDINATIONentity that closely
approaches the properties of a metal ion in a protein
and yields useful information concerning biological
structure and function. Given the fact that the term is
also loosely used to describe various types of molecular
structures, constructed, for example, in the computer,
the term BIOMIMETICis more appropriate.
modern synthesis The neo-Darwinism theory of evo-
lution. A modern theory about how evolution works at
the level of genes, phenotypes, and populations.
molarity The number of moles of solute dissolved in
1 liter of solution.
mold Molds are naturally occurring clusters of
microscopic fungi that reproduce by releasing airborne
spores. Certain individuals with a mold allergy will
develop asthma and nasal symptoms if they breathe in
these spores. Many people are allergic to mold. Mold
spores are carried in the air and can be present all year
long. Mold is most prevalent indoors, in damp loca-
tions and in bathrooms, washrooms, fabrics, rugs,
stuffed animals, books, wallpaper, and other “organic”
materials. Outdoors, mold lives in the soil, on compost,
and on damp vegetation.
See alsoFUNGI.
mole (mol) An amount of substance that contains as
many items (such as ions, molecules, etc.) as the num-
ber of atoms in exactly 12 grams of carbon (C). The
number of molecules contained is equal to 6.022 × 1023
(602,200,000,000,000,000,000,000), known as Avo-
gadro’s number. Thus a mole is anything that has Avo-
gadro’s number of items in it.
molecular formula The formula of a compound in
which the subscripts give the actual number of each ele-
ment in the formula.
molecular graphics The visualization and manipula-
tion of three-dimensional representations of molecules
on a graphical display device.
molecular modeling Atechnique for the investiga-
tion of molecular structures and properties using com-
putational chemistry and graphical visualization tech-
niques in order to provide a plausible three-dimensional
representation under a given set of circumstances.molecule The smallest unit in a chemical element or
compound that contains the chemical properties of the
element or compound. They are made of atoms held
together by chemical bonds that form when they share
or exchange electrons. They can vary in complexity
from a simple sharing of two atoms, such as oxygen,
O 2 , to a more complex substance such as nitroglycerin,
C 3 H 5 (NO 3 ) 3.molt The process of periodically losing old skin or
exoskeleton and replacing it with a new one. Reptiles
shed their skin, birds shed feathers, and butterflies molt
several times during their development.molybdenum cofactor(Moco) The molybdenum
complex of the MOLYBDOPTERIN PROSTHETIC GROUP
(LIGAND). In the molybdenum COFACTOR, the minimal
COORDINATIONof the Mo atom is thought to be pro-
vided by the chelating dithiolenato group of the molyb-
dopterin and either two oxo or one oxo and one sulfide
ligands.molybdopterin The PROSTHETIC GROUPassociated
with the Mo atom of the MOLYBDENUM COFACTOR
found in all molybdenum-containing ENZYMEs except
NITROGENASE. Many of the enzymes catalyze two-
electron redox reactions that involve the net exchange
of an oxygen atom between a SUBSTRATEand water.
The molybdopterin prosthetic group contains a pterin
ring bound to a dithiolene functional group on the
6-alkyl side chain. In bacterial enzymes a NUCLEOTIDE
is attached to the phosphate group.Monera The large prokaryotic kingdom that includes
archaebacteria, eubacteria, and cyanobacteria, members
of which were the first forms of life over 3.5 billion
years ago. All bacteria belong to the kingdom Monera.
See alsoBACTERIA.224 model