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~~~ REDUCING EQUIVALENT TRANSFERS ~~~
"Reducing Equivalent" = the form in which the electron
is transferred in oxidation/reduction reactions,
whether as [e-] or [H].
The particular type of reducing equivalent transferred
depends upon the reactants involved and upon certain
solvent characteristics such as polarity and pH.
When the reactive group transferred is meerely an electron [e-]
a difference in charge or valence only is noted
in the chemical equation.
When the transferred electron [e-]
is accompanied by a proton [H+]
then a hydrogen atom [H] is noted
as the reactive group transferred.
CONDITION: pH: SPECIES:
acidic -------- lower ------- [H]
alkaline ------ higher ------ e-
EXAMPLES: FADH2 + CoQ ---> FAD + CoQH2
AAH2 + 2Fe+++ ---> AA + 2Fe++ + 2H+
*Q- + O2 ---> Q + *OO-
NADH + FAD + H+ ---> NAD+ + FADH2
~~~ OXIDOREDUCTASES ~~~
- Most electron and hydrogen transfers which take place
in living things are facilitated or controlled by enzymes.
- As a general catagory such are called "OXIDOREDUCTASES".
- Specifically they are named according to their subtrates.
- The reductant is named first, then a colon,
then the oxidant, then the term "oxidoreductase".
EXAMPLES: * glucose-6-phosphate dehydrogenase
** glucose-6-phosphate : NADP+ oxidoreductase
* thioredoxin reductase
** NADPH : thioredoxin oxidoreductase
* glutathione peroxidase
** glutathione : peroxide oxidoreductase
* cytochrome a3
** cytochrone c : oxygen oxidoreductase
* xanthine oxidase
** xanthine : oxygen oxidoreductase
~~~ METABOLISM OF REDUCING EQUIVALENTS ~~~
Every important nutrient or reactive group in biological
chemistry has one or more metabolic pathways
which govern production, distribution, storage,
utilization, and elimination.
Examples are: amino groups, sulfur atoms, carboxylic acids,
purines, minerals, vitamins, glycerides, phosphates.
Similarly enzymatic pathways and control mechanisms exist
for the metabolism of electrons and hydrogen atoms.
To accomplish this, all living things use electron/hydrogen
carriers of various types.
These carriers are arranged and function in series known as
"electron transport chains".
Alternatively these may be called
"biological electron transfer sequences".
Reducing equivalents are passed from one carrier to the
next through these sequences under enzymatic control.
If a particular reaction produces electrons or hydrogen atoms,
biological electron transfer sequences are present
to carry them away.
If a particular reaction needs electrons or hydrogen atoms,
biological electron transfer sequences are present
to provide them.
~~~ EFFECTS OF ALTERED CONDITIONS ON BETS ~~~
CONDITION: REDOX: FUNCTION:
D & A normal- - - - - - normal - - - - normal
D increased - - - - - - redosis- - - - accelerated
D decreased - - - - - - oxidosis - - - inhibited
A increased - - - - - - oxidosis - - - accelerated
A decreased - - - - - - redosis- - - - inhibited
R & O decreased - - - - normal - - - - inhibited
R & O increased - - - - mixed- - - - - accelerated
toxic blockade- - - - - mixed- - - - - inhibited
component absence - - - mixed- - - - - inhibited
