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285 million people
worldwide have diabetes,
and about 10% of these
are Type 1. Type 2 diabetes
can be caused by a poor
diet and lack of exercise.
Magnificent molecules
In this issue: glucose
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Glucose
Sucrose
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4 | The Mole | May 2012
Prepare to be energised as Phillip Broadwith describes
one of life’s energy sources and explains its connection
with diabetes
Do you have a sweet tooth? Do you crave cakes, sweets
and sugary drinks? While these foods certainly won’t
keep you on good terms with your dentist, they will mean
that you should have plenty of energy, since sugars are
some of life’s most universal sources of energy.
Keeping control
made up of two different sugars, glucose and fructose,
joined together.
The strip is impregnated with an enzyme called glucose
oxidase, which oxidises one end of the glucose molecule
to form gluconic acid. This oxidation transfers electrons to
an iron-based molecule – also absorbed in the paper –
reducing it from iron(III) to iron(II). The amount of iron(II)
can be detected electrically by the meter and converted
into a blood sugar reading and an indication of the
required dose of insulin.
As glucose is such an important molecule, its levels
within our body must be tightly controlled. Too little
glucose in your blood (hypoglycaemia) can quickly lead
to unconsciousness or even death, and excess blood
sugar can be equally problematic. Blood sugar levels are
Sugars
controlled by two hormones, secreted by the pancreas.
The term ‘sugar’ in a scientific context refers to a huge
Glucagon stimulates the liver to break down glycogen, a
family of molecules, part of an even larger family known
as carbohydrates. This generally means they are strings of polymer which acts as a store of glucose. Insulin has the
opposite effect, and causes excess blood glucose to be
carbon atoms bearing multiple hydroxyl, or OH groups.
stored up as glycogen in the liver and muscles.
Sugars are simpler forms of carbohydrates, typically
If your body fails to produce sufficient insulin, then you
containing three to six carbon atoms. The most
common sugar is glucose, which has six carbons. It can have diabetes. Type 1, or insulin dependent diabetes,
exist as a straight chain, with an aldehyde group at one means patients must inject themselves with insulin every
end, but is more commonly found in its cyclic form as a day. To find out how much they must inject, they need
five or six-membered ring. The ring form is more stable, to measure their blood glucose level, using a personal
blood glucose monitor. The patient pricks their finger and
but in solution all three structures are present. The
white, crystalline powder that we would commonly refer soaks a drop of blood onto a paper testing strip, which is
then inserted into the meter.
to as ‘sugar’ is more properly called sucrose, and is
A source of energy
Life has evolved around glucose as its primary energy
source. It is used by most organisms, from bacteria to
humans. To extract the energy stored in glucose, it must
be metabolised or processed. This is done by a series of
enzyme-catalysed chemical reactions, the overall result
of which is to convert the glucose into carbon dioxide
and water, just like burning it would do. However, rather
than the uncontrolled release of energy as heat and light
that burning gives, metabolism produces adenosine
triphosphate, which is the molecule used to transfer
energy in biological systems.
Brain food
Since glucose is the only form of stored energy that
crosses the blood-brain barrier, it really is brain food. So
the next time you feel the need to justify that extra bit of
cake, have a good hard think – maybe about a difficult
chemistry problem. You’ll burn off the calories in no time.
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