| M
μ: Greek alphabet for m and pronounced mu like in mule. It is
used as the symbol for the distance represented by one micrometer, i.e.,
l0-4 cm.
macromolecule: a large molecule usually containing many smaller
units called monomers joined together end-to-end by covalent bonds.
Madelung constant: In ionic crystals, the mutual potential energy
of two ions (and electrostatic attraction) can be expressed by the sum
of two terms, one attractive—which extends to far distances—and one
repulsive—which falls off rapidly. The attractive term is expressed by
(Ae2z2)/R, where e is the electronic charge, z,
the valency and R, the smallest interionic distance. A is a constant
called the Madelung constant. It is always higher then unity, indicating
that each cation (or anion) is interacting not just with one single
anion (or cation) but other anions (or cations) further away also. Thus
A for NaCl crystal is 1.74756. A for Fluorite, М++Х2-,
is 5.3738.485 pp 507-508
magnetic resonance imaging, MRI: a way of visualizing the
interior of the human patient without surgery or exposure to harmful
X-ray based on the different NMR relaxation times or T1 and T2
of water protons in normal living cells and in cancer and other diseased
cells. Invented by Raymond Damadian using his original field focussing
technique, it was improved on by technical advances made by Paul
Lauterbur and others.
magnetization-demagnetization: The act of producing a cooperative
transition of ferromagnetic metals to the magnetized state by the
imposition of a strong magnetic field from outside is called
magnetization. Demagnetization means the opposite action of removing the
state of magnetization of the ferromagnetic materials.
magnetoelectric: characterized by electromotive forces developed
by magnetic means.
malignant tumor: cancer, a life-threatening abnormal growth,
which grows in an uncontrolled manner, and may proliferate and invade
normal tissues.
Malpighian tubule: any of a group of long blind vessels opening
into the posterior end of the alimentary canal of most insects,
functioning primarily as an excretory organ.
masked sites: Chemical groupings inherently capable of
interacting with ions or other solutes are not able to do so because
they are already occupied in some way and thus appear masked.
matrix protein, matrix protein system: a hypothetical system of
one or more protein(s) pervasively present throughout the living cell
One function of the matrix protein system is to maintain the bulk-phase
cell water in its normal state of polarization and orientation in spite
of local perturbations from time to time.
membrane fraction of crab-nerve homogenate: a suspension of
isolated crab nerves is first ground up in a (tight-fitting glass
pestle-glass tube) homogenizer, until a more or less homogeneous
suspension is obtained. By centrifuging the suspension at different
speed in an ultracentrifuge, different fractions of the homogenate can
be obtained. The fraction containing bits and pieces of materials
identified as the torn cell membranes is what is called the membrane
fraction of crab nerve homogenate.
membrane potential: a lasting electrical potential difference
theoretically postulated to exist across cell membranes or their models
on account of different permeability to ions of different electric
changes in the environment. (For evidence and other reasons, which deny
its existence in Nature, see [15.5(1.1.1)] and [16.6 (3.4)].}
membrane pump theory: In a later version of the membrane theory
after the demonstration that resting cell membranes are permeable to
sucrose, hydrated Na+ and other large solutes, pumps were
installed in the cell membrane to keep their intracellular
concentrations low. Among them, the most prominent pump is the sodium
pump.
membrane theory: a theory of the living cells as
membrane-enclosed dilute solutions introduced in the 19th century to
explain the osmotic swelling and shrinkage and other related cell
physiological manifestations.
metabolism: the sum total of chemical reactions occurring in a
living cell or organism by which energy is provided for vital processes
and activities, and new materials are assimilated to repair worn
structures and build new ones.
metastable equilibrium state: Like a coin standing on its edge, a
system in a metastable equilibrium state is in an equilibrium state but
not the most stable one. With relatively small perturbation, a system in
a metastable equilibrium state may topple into an alternative more
stable state.
meta-substitution: See para-substitution.
method of least squares: a statistical method of finding the best
fitting straight line or other theoretically-derived curve for a group
of experimental data points The method relies on finding the theoretical
curve which gives the smallest sum of the squares of the departure (both
positive and negative) of individual data points from the theoretically
predicted values.
methyl alcohol: methanol, wood alcohol, СН3ОН.
methylene group: -CH2-, a fundamental structural unit of
straight-chain or aliphatic compounds.
Michaelis-Menten kinetics: study of the rate of enzymatic
reactions with variation in the substrate concentrations, in the
concentration of competing agents, etc. Double reciprocal plots of the
rate of enzyme activity against that of the substrate concentration is a
key feature of these studies to obtain the quantitative data sought
after.
Michaelis' theory of enzyme activity: This theory is based on the
assumption that the rate of enzyme activity is directly proportional to
the concentration of the enzyme-substrate complex, which in turn is
related to the substrate concentration according to the Langmuir
adsorption isotherm.
microelectrode: a small electrode See Gerard-Graham-Ling
microelectrode, ion-specific microelectrode.
microinjection: injection of fluid materials into the interior of
a living cell with the aid of a glass capillary micropipette.
micrometer,
μ: a distance equal to 10-4 cm.
millimole, mmole: name for a specific number of molecules or ion
equal to one one-thousandth of the Avogadro number (2.02
× 1023), or a mole.
mitochondria: granules and filaments in the cytoplasm which may
be separated from the remainder of the cytoplasm by ultracentrifugation.
Mitochondria are the seats of many metabolic reactions. A major function
of mitochondria is to produce ATP. That is why in living cells they tend
to congregate near work-performing, energy-demanding cytological
structures like myofibrils.
mitochondrial inner membrane: Each mitochondrion as a rule
contains an outer membrane and an inner membrane. The inner membrane has
many inward directed folds or cristae. Inside the inner membrane is the
matrix in which much proteins as well as DNA and RNA are found.
mobility: rate of movement usually at molecular scale.
molal: of, or pertaining to, the concentration of a solute in
gram molecules dissolved in 1000 grams of the solvent.
molar: of, or pertaining to, the concentration of a solute in
gram molecules dissolved in 1000 ml of the solution.
molar volume, molecular volume: volume in cubic centimeters (cc)
of one mole of a chemical substance.
mole: the expression for a certain number of molecules or ions
equal to that of the Avogadro number, 2.02
×1023.
molecular switch: a molecular mechanism, which can turn on and
off certain physiological activity at the cell or below cell level.
molecular volume: See molar volume.
monactin: an antibiotic which combines reversibly and
preferentially with K+. It is known as a K+-specific
ionophore since its presence can dramatically increase the rate of
transport of K+ across phospholipid bilayers.
monochloroacetic acid: ClCH2COOH, acetic acid in which
one of the methyl hydrogen atom has been replaced by a chlorine atom.
monochromatic: having or consisting of one color, or in other
words having or consisting of electromagnetic wave of one specified wave
length.
monomers: the individual chemical units that forms a polymer when
joined together.
monosaccharide: a sugar that cannot be decomposed into simpler
sugars. They are polyhydroxy aldehydes and ketones. Examples: D-glucose,
D-galactose.
motional restriction: hampering and limiting the movement of some
substances.
MRI: short for magnetic resonance imaging.
mucosal surface: The surface of the epithelial cell layer in
contact with the intestinal content is called the mucosal surface,
whereas the other surface is called the serosal surface.
multilayers of polarized-oriented water: the dynamic structure of
multilayers of water molecules polarized and oriented by a checkerboard
of alternating negatively and positively charged sites or a matrix of
linear chains carrying altematingly negatively charged and positively
charged sites.
muscle fibers: muscle cells
mutation theory: the theory that in genetics, the attributes of
the offsprings are sometime altered by changes of the genes by a process
called mutation as a result of which, the DNA molecules involved are
altered chemically.
myocardium: the middle muscular layer of the heart wall.
myofibrils: one of the fine, longitudinal filaments making up a
muscle fiber Each myofibril consists of a linear sequence of individual
units called sarcomeres.
myoglobin: a red iron-containing protein pigment in muscle.
myoplasm: muscle cytoplasm.
myosin: the most abundant protein of muscle.
myosin B: a name once used to describe actomyosin.
|
