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Vitamins are chemicals
which are required in very small quantities to keep you healthy. If a
particular vitamin is missing from your diet you will suffer from a
deficiency disease. For example, if you have absolutely no Vitamin C you
will end up with a deficiency disease called scurvy. You will be cured
from the disease, if it is in the early stages, by eating things which
contain Vitamin C. It is not possible to catch a deficiency disease from
someone else.
Vitamins are all organic
chemicals. There are two groups of vitamins: those which are fat-soluble
only contain the elements carbon, hydrogen and oxygen; the water soluble
ones may also contain nitrogen and even sulphur. When they were discovered
they were given temporary names, starting with Vitamin A, then B, C, D and
so on. Then we discovered that Vitamin B was a mixture of several
different chemicals so they were given subscript numbers 1 to 12. We knew
what they did, but did not know their chemical composition. Even though we
now know their chemical names, we still use their temporary names. (I
don't know why we jumped from E to K.)
Here are the
vitamins required by humans:
| Vitamin |
Other Name |
Deficiency Diseases |
| A |
Retinol |
Xeropthalmia // Keratomalacia |
| precursor |
Carotene |
can be turned into Vitamin A |
| B1 |
Thiamin |
Beriberi |
| B2 |
Riboflavin |
|
| B3 |
Nicotinic acid |
Pellagra |
| B |
Pantothenic acid |
needed to make coenzyme A |
| C |
Ascorbic acid |
Scurvy |
| D |
Calciferol |
Rickets // Osteomalacia |
| E |
Tocopherol |
needed for growth and fertility |
| K |
Napthoquinone derivatives |
Delayed clotting & haemorrhaging |
You must know
about vitamins C and D for the London GCSE Syllabus.
You must know
about Nicotinic Acid for the London "A" Level Syllabus
Vitamins are not a chemical
group; i.e. they are not related to each other by having a common chemical
structure. As you can see in the table above, some are alcohols (-ol),
some are amines (-amine), and some are acids. They are a biological group
of chemicals, i.e. their similarity is that they are all necessary
components of a balanced diet and without them you develop deficiency
diseases. Vitamins do not have to be digested, they can be absorbed
directly from the gut contents.
Vitamin
C:
Scurvy was a serious
disease for sailors at sea. If they had a very poor diet with no fresh
vegetables or fruit for several months they ended up with scurvy. Of
course the Officers were able to eat a better diet so they were less
likely to get scurvy.
What happened to the
sailors was that cuts and bruises did not heal properly, their gums would
get inflamed and their teeth would start to fall out. Eventually they
would die from the disease. A British Naval Officer discovered that he
could prevent his crew from developing scurvy by making them drink lemon
juice. American sailors thought this a little bit funny and called the
British sailors "limeys" (they thought that it was lime juice).
When the Admiralty were
told about the effect of lemon juice preventing scurvy, their scientists
investigated. They realised that there was some chemical in the lemon
juice which prevented scurvy; they called the chemical Vitamin C. Now we
know that it is a chemical called Ascorbic Acid.
It is possible to estimate
the amount of Vitamin A in fruit juice using a chemical called TCPIP. This
is a blue dye which is decolourised by ascorbic acid. You can use it to
measure the amount of Vitamin C in fruit juice or vegetables. (This is not
possible with something like blackcurrant juice because you will not be
able to see the TCPIP lose its colour.) . So there are some possibilities
for an investigation on the amount of Vitamin C in various fruits,
vegetables, and juices. You could also investigate the effect of heat or
air on Vitamin C. PIDCP another name for TCPIP or a similar chemical?
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Vitamin
D:
This vitamin is concerned
with the absorption of Calcium. Without Vitamin D, calcium is just not
absorbed. When young children are deprived of Vitamin D they develop a
disease called rickets. It is very easy to understand this because you
already know that calcium is needed for growth of teeth and bones. If you
have rickets, your bones do not grow properly. Adults deprived of Vitamin
D develop a similar disease called osteomalacia.
What is more interesting
about Vitamin D is that it can be made in our skin providing that we get
enough sunlight. We all have some natural fat in our skin and in sunlight
this gets turned into Vitamin D. However, this depends upon how much
sunlight we get and how much pigmentation there is in our skin.
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You can also suffer from a
deficiency disease if one or more mineral salts are absent from your diet,
e.g. if you have no Iodine in your diet you will end up with a deficiency
disease called goitre. However, we do NOT call iodine a vitamin because it
is not an organic substance; we refer to iodine as an essential mineral.
Similarly there are essential amino-acids which must be present in the
protein which you eat.
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