carbon monoxide (CO):
a gaseous substance which binds as a ligand to numerous
metal cations including iron and copper. Carbon monoxide competitively
binds to heme and thereby profoundly inhibits the oxygen carrying
capacity of hemoglobin and myoglobin. It also profoundly inhibits
cytochrome A in the mitochondria where diatomic oxygen must be utilized
to produce ATP. It can be used in biochemical research as an inhibitor
of numerous enzymes which utilized certain metals in the active center.
carbonyl group (C=O):
any carbon and oxygen atom connected by a double bond
as in a ketone, aldehyde, carboxylic acid, glyoxal, or quinone.
carboxylic acid (R-COOH):
any organic acid having a carbon atom attached to
both an oxo group and a hydroxyl group. This arrangement can readily
release a hydronium ion (H+) to produce the carboxylate anion (RCOO-)
in which the electron is delocalized or shared between both oxygen atoms.
This enhances the stability of the anion and favors release of the
hydronium ion (H+) to the solvent or to other stronger base. Carboxylic
acids can be reduced by the addition of two hydrogen atoms to become
hydrated aldehydes.
carnitine ((CH3)3N+-CH2-CHOH-CH2-COOH):
N-trimethyl-gamma-amino-beta-hydroxy-
n-butyric acid; L-carnitine; a molecule which serves as a shuttle for
fatty acyl groups into the mitochondria. In the cytoplasm fatty acyl
groups are transferred from fatty acyl coenzyme A (R-CO-S-CoA) to the
middle hydroxyl group of carnitine forming an ester. This ester can
shuttle into the mitochondria. Once inside the reverse occurs as the fatty
acyl group is transferred to yet another molecule of CoA thereby releasing
the carnitine to shuttle back out. Intramitochondrial fatty acyl CoA
undergoes successive oxidation steps which produce FADH2 and NADH.
carotenoids:
medium to long chain turpenes naturally occuring in plants.
These can be red, orange, or yellow in color due to their long chains
of conjugated double bonds. These compounds are able to absorb the
energy of excitation of singlet oxygen. Many can be metabolized to
vitamin A which supports vision, healing of mucocutaneous tissues,
and immune function.
cascade:
a sequence or series of biochemical reactions or physiologic triggers.
catalase:
a type of peroxidase which like all peroxidases reduces hydrogen
peroxide to produce water. Catalase obtains electrons for this
reduction from yet another molecule of hydrogen peroxide thus
converting it to oxygen. The overall reaction is: 2 H2O2 --->
O2 + 2 H2O. Catalase has a very high reaction rate when large amounts
of H2O2 are present. Thus it has a protective role in living things
to guard against excessive H2O2 build up. Catalase is weakly inhibited
by high concentrations of its product O2.
catalyst:
a substance which increases the rate of a chemical reaction;
a reactant which is released again as a product in a reaction;
a material which lowers the threshold or activation energy of a chemical
reaction; a substance that facilitates the reaction of other molecular
species by bringing the reactive groups together.
catechins:
a polyphenol with a bioflavonoid structure found in numerous plants
especially green tea.
cation:
a positively charged molecular species; the type of ion which is
attracted electrostatically towards the cathode or negative plate.
cathode:
the negative plate or electron releasing plate or reductive plate
of an electrochemical cell or vacuum tube.
ceruloplasmin (CP):
a blue colored protein rich in copper which is synthesized in the
liver and released to varying degrees into the blood.
Certain cytokines stimulate the enhanced release of CP during conditions
of infection or inflammation. CP delivers copper to peripheral tissues
for utilization. Ascorbic acid stimulates the release of copper cations
from CP by reduction. CP oxidizes numerous phenols, polyphenols, and
hydroquinones. CP eliminates superoxide. Wilson's disease is a genetic
disorder attributable to failure to synthesize CP resulting in disturbed
copper distribution and utilization, and enhanced susceptibility to
copper overload and toxicity.
cesium (Cs):
a heavy alkaline metal in series below rubidium (Rb),
potassium (K), sodium (Na), and lithium (Li). Cesium
has been found to alter transmembrane hydronium (H3O+)
transport resulting in high intracellular pH especially
in tumor cells. This has been found to correlate with
tumor regression, whenever a pH of 8 or higher is achieved.
Incidently, this is the same pH range in which thiols (RSH)
deprotonate to become thiolate anions (RS-). Of all naturally
occuring reactive groups in living things, thiolate is among
the most sensitive to oxidation.
chelate:
an organic molecule with two or more reactive groups capable of
binding as ligands to metal cations. The metal cation chelate complex
renders the cation more soluble and mobile thus facilitating its
transport into, within, or out of the body. Chelating agents can be used
medicinally to detoxify metals and biochemically as inhibitors of enzymes
which require metals to function. Such chelators usually abstract the
cationic metal from the enzyme.
chlorine dioxide (ClO2):
a yellow gaseous substance composed of two atoms of oxygen covalently
bound to each one atom of chlorine. It has one unpaired electron, but
is unusually stable as a free radical and has no tendency to dimerize.
It smells exactly like elemental chlorine (Cl2). In higher concentrations
ClO2 is explosive. It is highly soluble in water. It is a potent oxidant
which can release one or two atoms of monoatomic oxygen to numerous
reactants or take up electrons from numerous substances. Chlorine dioxide
is often reduced in a one electron step producing the chlorite (ClO2-)
anion, however, under many circumstances it can be reduced all the way
to chloride (Cl-). Like ozone, ClO2 is useful to disinfect drinking water
and is a potent antiinfectious agent. Unlike elemental chlorine (Cl2),
chlorine dioxide (ClO2) does not produce chloramines nor halomethanes.
ClO2 preferentially reacts with ferrous (Fe++), manganous (Mn++),
thiols (RSH), aldehydes (RCHO), phenols (ArOH), secondary amines (RNHR')
and tertiary amines (RNR'R").
chlorate (ClO3-) anion:
a molecular species composed of one atom of chlorine three covalently
bound oxygen atoms and one electron. Chlorate is usually available
as the sodium salt (NaClO3). It is much more stable than chlorine
dioxide (ClO2), chlorite (ClO2-) or hypochlorite (ClO-). To become
reactive it usually requires acidification with a strong acid.
However, it can react with certain reductants without acid.
chlorite (ClO2-) anion:
a molecular species composed of one atom of chlorine two covalently
bound oxygen atoms and one electron. Chlorite is usually available
as the sodium salt (NaClO2). Chlorites can oxidize ferrous (Fe++)
and thiols (RSH). Upon acidification chlorite (Cl)2-) takes up one
hydronium cation (H+) to form the unstable chlorous acid (HClO2),
which disproportionates producing chlorine dioxide (ClO2) primarily
and other oxides of chlorine.
chlorous acid (HClO2):
a neutral molecule composed of one atom of chlorine, two atoms of oxygen,
and one atom of hydrogen; the conjugate acid of the chlorite (ClO2-) anion.
Chlorous acid is unstable and considered a reactive intermediary species.
It readily oxidizes ambient chlorite (ClO2-) producing chlorine dioxide
(ClO2) and dichlorine dioxide (Cl2O2) another unstable intermediate.
chromium (Cr):
a multivalent transition metal whose trivalent cation is important
in cholesterol metabolism and in the activation of insulin receptors.
citric acid:
a tricarboxylic acid and part of the Kreb's cycle. Citric acid
is also a chelator and an inhibitor of the prooxidant effects
of ceruloplasmin.
coenzyme A (CoA):
a complex mononucleotide type coenzyme consisting of the
following covalently bound parts listed in order: adenine, sugar,
phosphates, pantothenic acid, 2-aminoethylthiol (beta-mercaptoethylamine).
Its main function is to carry acyl groups at the thiol end. CoA is
the donor of acetyl groups to the Kreb's cycle. CoA holds fatty acyl
groups in both the synthesis and the oxidative degradation of fatty acids.
CoA delivers both the acetyl groups and the acetoacetyl groups in the
synthesis of beta-hydroxy-beta-methylglutaryl CoA (HMG-CoA), which is
subsequently reduced to free the CoA and produce mevalonic acid,
a precursor to various isoprenoids. The unacetylated thiol form of CoA
is able to redox cycle forming disulfides with glutathione, cysteine,
and other thiol containing compounds including proteins. Many functions
of CoA are thus reversibly inhibited by pro-oxidant conditions due to
this temporary binding phenomenon.
coenzyme Q (CoQ):
ubiquinone.
cofactor:
a substance necessary to the function of an enzyme besides the
substrate(s) of the reaction(s) it catalyses. A few examples follow:
magnesium in kinases; FAD, Fe+++ or Cu++ in various oxidoreductases;
glutathione in glyoxalase; pyridoxal phosphate in transaminases.
conjugated dienes:
an oxidatively modified polyunsaturated fatty acid having
two double bonds seperated by only one single bond, unlike the original
state in which all double bonds are separated by two or more single bonds.
To produce conjugated dienes a polynsaturated fatty acid must first
undergo abstraction of an allylic hydrogen atom between two double bonds
thus producing a carbon centered free radical. The loan electron can shift
positions to the opposite side of either adjacent pi bond as the effected
pi bond correspondingly shifts towards the middle. If the radical is
reduced while existing in this shifted position, the two double bonds
remain locked in the shifted position seperated by only one single bond.
Thus they are conjugated.
conjugated pi bonds:
an alternating system of single and double bonds such
that all the sigma bonds and atoms involved lie in the same geometric
plane which condition allows the pi bonds to interact; pi bonds which are
electrically, magnetically, and chemically interactive. Conjugated pi
bonds delocalize charges and/or unpaired electrons by allowing them to
shift positions or to resonate among various positions. This makes these
molecular species more energetically stable than their nonconjugated
analogues and so facilitates the production of charged or radicalized
states. Conjugated molecules upon reaction yield a variety of products
corresponding to each shift in the position of the reactive group
involved. Conjugation facilitates many redox reactions by making the
semireduced radical intermediaries more easy to form.
copper (Cu):
a transition metal having three valences namely zero, +1 and +2.
Copper cations readily redox cycle making these useful and essential
to many biological redox reactions. Numerous oxidoreductases have an
absolute requirement for copper as a cofactor. Freely soluble copper
can generate oxyradicals, whereas enzymatically bond copper is used
in certain enzymes to detoxify oxyradicals.
coupling:
a reaction in which two free radicals combine to form a non-radicalized
product; free radical quenching by the addition of another of the
same type or a different type of free radical. Note that when the
unpaired electron of each of any two free radicals come into close
proximity, they tend to pair up and form a new covalent bond.
covalent:
a type of chemical bond in which the electrons are shared between
the two atoms involved. Covalent bonds involve two electrons which
are of magnetically opposite orientation or spin. Two types of covalent
bonds exist the sigma and the pi. The sigma is the more energetically
stable and the stronger of the two.
Crabtree effect:
inhibition of cellular respiration by high concentrations of glucose.
crenation:
the response of a red blood cell when placed into a hypertonic
solution by shrinking which causes the membrane to appear wrinkled.
Energetically fit and healthy RBC's are relatively more hypotonic
as compared to weaker cells. Thus healthier cells tend to crenate
more readily making crenation an easy functional test of cellular
energy fitness and ATP production.
cupric cation (Cu++):
the species of copper in the plus two valence state.
cuprous cation (Cu+):
the species of copper in the plus one valence state.
curcumin:
a bright yellow compound naturally occurring in turmuric, which has
been found to possess antiinflamatory and antioxidant properties.
It carries a two monophenol groups (one at each end of the molecule)
which can quench oxyradicals.
cyanide anion (CN-):
a molecular species composed of one atom of nitrogen
and one atom of carbon connected by a triple bond and negatively charged.
Cyanide strongly binds as a ligand to verious metal cations. Numerous
enzymes which employ metals as cofactors are profoundly inhibited by
cyanide which is the mechanism of cyanide's extreme toxicity.
cysteine (cys):
an amino acid which bares a thiol group in its side chain.
This thiol group is part of and essential to the function of numerous
enzymes including many oxidoreductases. Mercury II (Hg++) is highly
reactive with the thiol group of cysteine and binds to it tightly
which mechanism partially explains the extreme toxicity of Hg++.
Many proteins include two cysteines in proximal orientation when first
synthesized by the ribosomes. These autooxidize and couple to produce
a disulfide bridge which stabilizes the structure of many proteins.
This situation is reversible such that the redox status of the medium
in which such proteins are suspended controls the structure and / or
the activity of the protein. The result is a receptor, an enzyme, or
a cell signal mechanism whose function is sensitive to the redox balance
of the ambient medium.
cystine:
a disulfide produced by the oxidative coupling of two cysteines.
cytochrome:
a protein which functions as an oxidoreductase having a distinct
UV-vis spectrum due to the presence of its reactive group, a porphin
analogue with a cationic iron atom at the active center. Cytochromes
redox cycle as the iron shifts between its ferric (Fe+++) and its ferrous
(Fe++) valence. Cytochrome A is unique in utilizing copper besides iron
in the active center, copper being the site at which diatomic oxygen is
utilized as a final electron receptor. Tiny diatomic ligands such as
azide (NN-), carbon monoxide (CO), cyanide (CN-), and bisulfide (HS-)
can bind to the copper and defeat oxygen utilization.
cytochrome P 450:
a specialized cytochrome exhibiting strong absorbtion at
the 450 wavelength when reacted with carbon monoxide. This family of
enzymes can be found in complexes which add one atom of oxygen to
various substrates.
cytochrome P 450 reductase:
a flavoprotein which shuttles two hydrogen atoms
into the cytochrome P 450 complex. These are used to reduce one of the
atoms of diatomic oxygen producing water (H2O) from it. The other atom
of oxygen becomes an adduct to the substrate.
cytokine:
a family of peptide cell-to-cell signal molecules which function
to regulate numerous activities of the immune system.
cytoplasm:
the part of the living cell inside of the outer membrane but
outside of the nucleus. The cytoplasm is composed of a solution of various
metabolites and electrolytes, a colloidal suspension of various proteins
and enzymes, and various organelles.
