Chemistry Reference
In-Depth Information
O
H
(CH
2
)
6
C
OC
2
H
5
(CH
2
)
6
CH
3
H
Figure 8.16
The structure of ethyl oleate.
saponification values) as well as physical methods of assay such as determin-
ation of density (i.e. weight per millilitre) and measurement of their refrac-
tive index. Increasingly, modern instrumental methods of analysis, such as
gas chromatography, are being used to identify component oils and ensure
purity (e.g. see the BP assay of Arachis Oil).
Ageing
The effects of oxygen are not limited only to the oxidation of small
molecules found in drugs and medicines. It is now thought that most of the
chemical effects of human ageing are as a result of sustained and cumula-
tive oxidative damage on important macromolecules present in our cells
(particularly DNA). The old joke to the effect that air is poisonous -
everyone who breathes the stuff dies - does have some truth in it. As soon
as we are born, the cells in our bodies begin to suffer damage from reactive
oxygen species (such as hydroxyl and superoxide radicals). These reactive
species are formed by the breakdown of oxygen present in all our cells and,
once formed, can react with essential cell components such as phospholipid
membranes, cellular proteins and DNA. Damage to DNA results in genetic
mutations, which can be passed on to subsequent generations of cells. If the
oxidative damage is severe, the cell in question will enter a programme of
cell death, called
apoptosis
, and effectively commit suicide.
To counteract these onslaughts by reactive forms of oxygen, the body
has evolved a number of elegant defence mechanisms. Repair enzymes can
detect damaged DNA bases and repair them
in situ
without disrupting the
function of the DNA. Similarly, damaged membrane is repaired to restore
cell integrity. These repair enzymes are essentially catalysing an intracellular
REDOX process and require a number of essential nutrients such as vita-
mins C and E to act as antioxidants. The ageing effects of oxidative damage
cannot be reversed (yet!) and no amount of expensive cosmetic preparations
will stop skin from ageing, but the amount of damage to cells may be
reduced by an adequate intake of vitamins and antioxidants in the diet. The
most recent nutritional advice is to consume at least five helpings of fresh
fruit and vegetables every day to maintain an adequate dietary intake of
