15. Vitamins, drugs - analgesic
medicines, food additives
& some cooking chemistry!
Brown's GCSE/IGCSE/O Level KS4 science-CHEMISTRY Revision Notes
What are vitamins?
Drugs-medicines we regularly use! What are food additives used for? How safe are
colourings, flavourings preservatives and sweeteners? What are E numbers? What
is intelligent packaging and active packaging of food? Aspects of cooking
GCSE level chemistry revision
All my GCSE level oil and organic chemistry revision
All my advanced A level organic chemistry notes
brown - comments - query?
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in analgesic medicines
Additives, Intelligent Packaging and Active Packaging of Food
A footnote on cooking chemistry !!
Vitamins, Drugs-analgesic medicines and Food Additives
What are vitamins?
particular essential molecules with particular roles in living systems
which are NOT proteins, carbohydrates, fats or mineral salts.
If you have a good balanced
diet, you shouldn't, in theory, require any extra dietary supplements.
However, to help avoid potential
vitamin deficiency certain vitamins are added to particular foods such as
bread, margarine, breakfast cereals, milk powder etc. to replace vitamins
destroyed during food processing or to make good a natural deficiency.
One of the most important
ones in any diet is Vitamin C or Ascorbic Acid. Its
structure is related to 'simple' sugars but humans are one of the few
mammals that are unable to synthesise vitamin C.
It is essential for healthy
tissue and one of its functions is the removal of dangerously reactive
chemical species called free radicals (see further on).
Vitamin C is present in
fruit and vegetables but the amount is reduced by prolonged storage and
250 years ago, as many as 2/3
of a ship's crew died from vitamin C deficiency causing scurvy. In 1747 it was
decided to give sailors citrus fruits to recover from scurvy but wasn't until
later that vitamin C was recognised.
In contrast to the other
water-soluble vitamins, vitamin C has no clear cut role as a catalyst or
part of an enzyme. It does, however, have a range of other important
Collagen formation. Vitamin C
in collagen formation which is found wherever tissues
require strengthening, especially in tissues with a protective,
connective, or structural function. Collagen is critical to the
maintenance of bone and blood vessels and is essential in wound healing.
Antioxidant activity. Ascorbic acid can act as an antioxidant by
donating electrons and hydrogen ions, and reacting with reactive oxygen
species or free radicals.
Iron absorption. Vitamin C is important for the effective absorption
of iron and reduces iron(III) Fe3+ to iron(II) Fe2+.
It helps in the
synthesis of vital cell compounds. During times of physical and emotional stress, as well as during
infection, there is increased production of oxygen radicals. Therefore
there is increased reliance on vitamin C's activity as an antioxidant.
Vitamin C is vital for the function of the
immune system, but the effectiveness of large doses of vitamin C in preventing and alleviating
the symptoms of the common cold is still a matter of debate.
Two of the earliest signs
of deficiency (prevention of collagen synthesis) relate to its roles in
maintaining the integrity of blood vessels. The gums around the teeth
bleed more easily, and the capillaries under the skin break
spontaneously producing tiny haemorrhages. If you are short of vitamin C
for say 20 days, scurvy can develop and is characterised
by further haemorrhaging, muscles depletion, rough-brown-dry-scaly skin, deep
bruising. Wounds fail to heal properly and bone fails to rebuild properly
too and you are further likely to suffer from anaemia and infections.
Vitamin A1, A2 and the fat soluble vitamin D
group are found in fish oils.
Vitamin E is found in some vegetable oils
The B group of vitamins
are mainly concerned with metabolism ie the utilization and release of
energy from foods.
EAT your fruit and veg 'guys' (as well as a few
AND keep your health and still pass those dreaded exams!!!!
For some examples read the section on food packaging
labels further down the page in the food additives section.
TOP OF PAGE
15b Drugs e.g.
in analgesic medicines
Drugs can be defined as
an externally administered substances which modifies or affects chemical
reactions in the body, usually for the bodies greater well-being. Poisons
can be defined in the same way, but hopefully not intentionally and have
undesired effects! A 'drug' is a specific
molecule with a particular pharmacological or physiological action on an
organism/animals chemistry and a medicine is the complete formulation of
the means of administering the drug to a patient i.e. the method of
drugs used to reduce pain and are a type of anti-inflammatory agent.
The molecular structure of
three well known analgesics are shown in the diagram below.
All are used for
'headache' treatment, and hopefully using this website and others
will help minimise their use!
The central hexagonal
ring of 6 carbon atoms is called a 'benzene' or 'aromatic' ring. The 4th
outer electron of carbon (group 4) is delocalised, so the expected 4th
bond per C atom forms part of a 'communal' system (more on this at
advanced level, but the covalence rule of 4 for carbon is not broken!,
you have seen this situation before, check out
You can show a benzene ring as a simple hexagon with a circle in it)
+ NaOH ==>
e.g. An extract of willow
herb extract can be made from the leaves, bark and seeds of the
willow tree. Amongst other ailments it was given to help curing feverish
headaches and relief of pain in childbirth. When ingested the body
hydrolyses and oxidises the naturally occurring 'precursor' molecule to
form salicylic acid* which is the 'active' molecule in the body.
in the 1890's the German chemist Hoffmann experimented with various
chemical modifications of salicylic acid and found the best and
chemically stable form was 'aspirin' (shown below). He tried the
variations on his own father! who survived to provide valuable 'clinical
trials' - hardly acceptable these days! * 'Oil of winter green' from
certain plants is the methyl ester of salicylic acid and has similar
Aspirin (and the others
shown) are not very soluble in water. Soluble
aspirin is made by neutralising the carboxylic acid with the alkali
sodium hydroxide to make the much more soluble sodium salt of the
acid. The reaction, using skeletal formula, is shown in the diagram below the three
analgesic drug structures.
New drugs and testing
Patents are taken out to
protect the company's commercial interests in the new medicine.
There can be a range of
formulations of a particular medicine when you buy it over the counter e.g. tablet of 100% aspirin, soluble aspirin (via Na+ salt of the acid
from neutralisation) and aspirin might form part of a mixture including
substances that have other beneficial effects.
The main point here is that
aspirin, like many drugs, can have multi-functional effects, hopefully
BUT this, sadly, is not
always the case, because with any new drug there is always the
danger of unknown side-effects.
Therefore there is a
tremendous responsibility on pharmaceutical companies to ensure the
development of safe and effective drugs.
Lots of time and money
spent on discovering and developing new drugs and there are lots of
factors to consider:
From the discovery of a
potentially useful molecule, sometimes called the 'lead molecule',
which can be from natural source or produced in some other project
Is there room in the
commercial market place for it?
Do research to see
if its safe, otherwise further development is a waste of time
and money or if not safe, can its molecular structure be
Can the modification
be safe? and more effective?
In what form, can it
be/needs to be, administered in? for clinical trials.
trials in various phases, noting particularly if any side-effects
which may be harmful.
Do you test new
drugs on animals? - an emotive issue, can non-animal testing always
allow the safe development of new products?
Do you test new
drugs on patients in a life threatening situation, give them a last
chance at some risk?
Patient health and
safety issues versus very big drug company commercial interests are
a matter of public concern.
Any new drug must
finally pass all the tests before legally licensed for patient
TOP OF PAGE
Additives, Intelligent Packaging and Active Packaging of Food
Some examples of nutritional
information on various foods
Food additives are
chemicals added to food to give particular effects e.g.
flavourings preservation and sweetening.
All the improvements in flavour, colour and making them last longer (longer
shelf-life), are all about improving the consumers eating experience.
Personally I prefer natural flavours and freshly cooked food, salads and
fruit as far as is possible, but I'm retired and don't have the same busy
life-style as when I was teaching in the laboratory and classroom!
The addition of some of them is controversial i.e. health concerns like
nitrates are carcinogenic, food colourings causing behavioural problems, but
proving these 'cause and effect' claims are not easy.
Colourings to make
food more attractive, more appetising, to fit in with the consumers perception of what it
should look like.
Flavourings to make
food more 'tasty', less 'bland', and to fit in with the consumers
perception of what it should taste like.
Preservatives are to
increase the 'shelf-life' of packaged food, decrease risk of food
poisoning by inhibiting bacteria/microbe growth (e.g. salt).
prevent oxidation of oils/fats by oxygen in the air, so helping preserve
food, giving it a longer shelf-life. Oxygen from air reacts with
food and the
oxidation causes deterioration in quality and taste.
bitterness or pander to our taste!
stabilisers help keep a mixture of ingredients together i.e. prevent
oily/fatty components separate out fro water/aqueous based components.
Emulsifiers oil and water
based food components blend together e.g. like in mayonnaise and ice
Processed foods that use
emulsifiers include salad cream, biscuits, toffee, bread, extruded
snacks, chewing gum, margarine / low fat spreads, breakfast cereals,
frozen desserts, coffee whiteners, cakes, topping powders,
desserts / mousses, dried potato, peanut butter, soft drinks, chocolate
coatings, caramels etc. etc.
Emulsions provide better
texture, coating ability and appearance, for example in salad dressings, ice
creams, cosmetics and paints.
Aqueous solution chemistry (section on emulsions)
emulsifiers in margarine.
has become more and more important as consumers demand a greater variety of
products which are increasingly sold through super-markets.
A variety of food packing
methods are used, variously described as e.g. intelligent packaging or
active packaging etc.
If the packaging is
air-tight no harmful bacteria can get in.
Excess water can be
removed which inhibits the growth of mould or bacteria.
Air/oxygen can be
removed or replaced with an unreactive gas like nitrogen/carbon dioxide, to
stop oxidation of the food AND removes the need to use antioxidant
E-numbers are reference numbers used by the European Union to
help identification of food additives.
All food additives
allowed and used in the European
Union are identified by an E-number.
The "E" stands for
"Europe" or "European Union".
Normally each food
additive is assigned a unique number, though occasionally, related additives
are given an extension (e.g. a,b,i or ii etc.) to another E-number.
The Commission of the European Union
assigns E-numbers after the additive
is cleared by the Scientific Committee on Food (SCF), the body responsible
for the safety evaluation of food additives in the European Union. A
summary is given below.
- E200-299, preservatives
- E300-399, anti-oxidants,
phosphates, and complexing agents
- E400-499, thickeners, gelling
agents, phosphates, emulsifiers
- E500-599, salts and related
- E600-699, flavourings
- E700-899, not used for food
additives (used for animal feed additives!)
- E900-999, surface coating
agents, gases, sweeteners
- E1000-1399, miscellaneous
- E1400-1499, starch derivatives
- E-numbers are only used for substances added directly to food products, so
contaminants, enzymes and processing aids, which may be classified as
additives in the USA, are not included in the E-number system.
- There is an EU directive on food
labelling which requires food additives
to be listed in the product ingredients whenever they are added for
- This includes colouring, sweetening and
enhancement as well as for preservation, thickening, emulsifying and the
- Ingredients must be listed in descending order of weight, which means
that are generally found close to the end of the list of ingredients.
- However, substances used in the protection of plants and plant products,
flavourings and substances added as nutrients (e.g., minerals, trace elements
or vitamins) do not need to be included in the ingredient list.
this, some substances that are regulated as food additives in other
countries may be exempt from the food additive definition in the EU.
The Food Standards Agency (FSA)
is an independent food safety watchdog that advises the government and the
public about food safety and health and issues guidelines on the maximum
amount of salt you should take in a day. This is known as the 'Guideline
Daily Amount' (GDA). Two government departments,
Department of Health and the Department for Environment, Food and Rural
Affairs, are both involved with food safety issues and do risk assessments
to check on the safety of chemicals used in food and advise the public on
how food, and food additives may affect their health.
In terms of food labelling, the main nutritional guideline shown on food
packaging is the GDA or RDA (recommended daily intake).
The GDA/RDA are the amounts of
nutrients that an average adult should eat each day in a healthy balanced
The amounts are quoted in grams
micrograms per 100g or 'helping' and converted to %RDA or %GDA, see examples
of nutritional labelling of food products below.
Spread 1 is made from vegetable fat and olive
oil. Apart from the oil/fat composition you have all sorts of additives e.g.
emulsifiers, salt, preservative, thickener, flavourings, colouring and vitamins.
The labelling on this fat spread 2 made from
vegetable oil is packed with nutritional information. Again, apart from the
oil/fat composition there added vitamins, salt, water, emulsifiers, flavourings
Baked beans mainly consists of water (by
deducting all the g from a 100g). The rest is main carbohydrate from the beans,
but there is some protein and a little added salt.
Cereal 1, like most cereals, is largely made up
of carbohydrate from the original grain and a little added sugar (total 64%).
All cereals have vitamins and minerals added (see Cereal 2 below)
Cereal 2 This cereal is designed for someone with
a sweet tooth (children!), the carbohydrate content from the original grain is
only 28.5% and the energy values increases a further 50% by adding sugar.
However, there are lots of additives in the way of vitamins and minerals like
iron and calcium for bone growth
Orange juice usually contains a good portion of
vitamin C, either from the original fruit or added.
TOP OF PAGE
15d A footnote on cooking chemistry !!
more aspects of cooking chemistry!
- Does cooking involve chemical changes?
- The answer is yes! There are lots of ways to
cook food e.g. baking, boiling, frying, grilling, steaming on cooking rings,
heated ovens, microwaves etc.
- All of these involve heating the food and
all involve complex chemical changes and in effect produce new substances
with a different molecular structure.
- When the cooking is complete, you cannot go
back to the original ingredients, cooking involves irreversible chemical
- Some examples of chemical changes in cooking
Cooking eggs or meat
Food is cooked for
The high cooking temperature
kills harmful microbes-bacteria, as long as cooked for the required time
at a high enough temperature. Food poisoning is all too common from
eating under cooked food. Some foods are actually poisonous when raw, but
cooking renders them edible and safe to eat e.g. red kidney beans must be
boiled for at least 10 minutes to destroy a poisonous substance and
preferably cooked for a further two hours - safe and nutritious!
It may improve the
texture, which is important in your appreciation of food, its not
just about taste.
It may improve the
flavour and taste (but remember some foods might taste better raw e.g.
It makes it easier
for the body to digest the food because it begins the 'breaking-down'
process, which your digestion system will complete.
Protein heat degradation
Most of meat from
animals consists of protein together with smaller amounts of water and fat.
Eggs and fish are also good sources of protein.
have a definite shape (diagram 1. above).
During the cooking of
meat irreversible chemical changes take place.
The complex and
specific structure of protein molecules is partly broken down in the
cooking process (diagram 2.).
The high cooking
temperature promotes particular chemical reactions to happen.
The structure changes
and some of the chemical bonds are broken and new molecules can be formed
that have a different taste-flavour and texture giving the food its own
characteristic 'cooked' character.
The breaking down of
protein complex protein molecules is called denaturing.
A similar process
happens in the cooking of carbohydrate foods like potatoes which are broken
down into far more readily digestible molecules - see below.
Potatoes are a good source
of carbohydrates, hence a good source of energy for the body.
BUT, potatoes are plants and
potato cells are surrounded by a rigid cellulose wall which we can't
digest, so we can't get to the starch that we can digest.
So, although raw potato is not easily
digested, cooking partially breaks the structure of potato down so
that we can digest it AND cooking also improves the texture and taste of
the potato to make it more palatable to eat.
In the cooking process the
plant cell walls of cellulose are softened and this allows hot water to
penetrate the cells.
Further cooking causes the
starch granules (starch grains) to swell and gelatinize as they absorb hot water.
This eventually causes the
cells to separate producing the soft texture of well-cooked digestible
Mash with milk, butter and
salt to suit taste! Cheap and yummy!
Since fats and oils are important to our
diet, there is the ever present danger of over-consumption (speaking as
someone who loves chips and spicy crisps!).
Vegetable oils are an important
source of energy and even vitamins like vitamin E in seed
Vegetable oils contain
essential fatty acids which are bodies need for certain metabolic
So we need both oils and fats as sources of
important essential fatty acids and energy.
Because vegetable oils
have much higher boiling points than water, all the 'cooking
chemistry' is speeded up, so, cooking time is reduced at this higher
temperature when using vegetable oil compared to water.
is a price with this high temperature faster cooking, 'sensitive'
molecules like vitamin C and other nutrients can be destroyed.
On the other hand, we
get food with a different flavour and we do seem to naturally like
Some of the flavours
from the food get dissolved in the oil and contribute to the taste
Cooking food in oil
automatically increases the energy content of the meal - oils are
high calorie foods!
We need both saturated and unsaturated
fats or oils.
It is recommended that we do not
overdo the fat intake but we do need both saturated and unsaturated
See also the
biofuels section in the alcohol notes
Oils, fats and margarine notes
bread and cooking cakes etc.
on raising agents in cooking
An alternative to
yeast (which produces carbon dioxide by fermenting sugar) is to use
hydrogencarbonate ('sodium bicarbonate' or 'baking soda')
where you want a rising action in
baking e.g. cakes.
When baking powder is
heated it undergoes thermal decomposition.
The 'rising action'
is due to the formation of carbon dioxide gas as the sodium
hydrogencarbonate breaks down when heated.
sodium hydrogencarbonate ==>
sodium carbonate + water + carbon dioxide
2NaHCO3 ==> Na2CO3
+ H2O + CO2
You can use the simple
apparatus shown above-right to investigate the decomposition of sodium
hydrogencarbonate and carry out the simple limewater test for carbon
using self-raising flour, the rising action is also due to carbon dioxide gas
formed from its reaction with an acid (e.g. tartaric acid), and nothing to do with enzymes:
baking powder = sodium hydrogencarbonate + a solid
harmless organic acid,
the reaction is ....
hydrogencarbonate + acid ==> sodium salt of acid +
water + carbon dioxide gas
This will be faster
process because when water is added to the baking mixture it will
facilitate the reaction between the harmless organic acid and the
sodium hydrogen carbonate.
You can investigate
mixing a self-raising flour with hot or cold water using the simple
apparatus shown on the right, and again test for carbon dioxide gas
for the carbon dioxide
Multiple Choice Quizzes and Worksheets
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products
KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry
3 linked easy Oil Products gap-fill quiz worksheets
ALSO gap-fill ('word-fill') exercises
originally written for ...
... Ex AQA GCSE Science
Useful products from
crude oil AND
Ex OCR 21st C GCSE Science
Worksheet gap-fill C1.1c Air
pollutants etc ...
... Ex Edexcel GCSE Science
Crude Oil and its Fractional distillation
... each set are interlinked,
so clicking on one of the above leads to a sequence of several quizzes
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9-1 chemistry science topics modules for studying
why do we need Vitamins?, what is a Drugs, how do analgesic medicines work,
use of safe Food Additives in food, what do we mean by intelligent
Packaging, what is Active Packaging of Food, why is Vitamin C is essential
for us humans, useful examples of drugs like aspirin, paracetamol,
ibuprofen, what are E numbers? why are they important, chemistry revision
notes igcse revising KS4 science