Food Matters Quick Revision
What chemicals are living things made from?
Many chemicals in living things are natural polymers.
Two important natural polymers are:

Carbohydrates – for example, cellulose, sugars and starch. These are made from the
elements carbon, hydrogen and oxygen.

Proteins – amino acids joined together in long chains. They are made mainly from carbon,
hydrogen, oxygen and nitrogen.
How do elements cycle through living organisms?
Living things take in chemicals by photosynthesis, breathing, absorbing and eating. Decomposers,
like microbes and fungi, break down dead plants and animals. These processes recycle the
materials in living things.
There are nitrogen atoms in the protein molecules of all cells. These atoms are used over and over
again by different organisms.
Elements such as, phosphorus, potassium, nitrogen and carbon are continually recycled.
How are intensive and organic farming different?
Farmers use the same land every year to grow food crops. When farmers harvest crops, the soil
loses nitrogen, phosphorus, and potassium compounds. Farmers must replace these elements; if
they don’t, soil fertility decreases and the land produces less food. Pests and crop diseases can
also reduce crop yields.
Intensive farmers produce as much food from their land as possible. They aim to maximize yields
by:
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Adding synthetic fertilizers to replace soil nutrients
Adding pesticides and fungicides to kill pests and disease-causing fungi
Adding herbicides to kill weeds that compete with crops for nutrients, light and water
Organic farmers believe that that intensive farming is unsustainable. Synthetic fertilizers do not
recycle nutrients.
Nitrates from fertilizers may be washed into rivers if misused.
Pesticides kill useful animals as well as animals that damage crops and disrupt food chains.
Organic farmers take care to produce food without damaging the environment. They follow UK
national standards.
Organic farmers:
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Add manure to replace soil nutrients
Use natural predators to control pests
Rotate crops to replace soil nutrients naturally and to reduce crop diseases
Where do harmful chemicals in foods come from?
Some plants contain harmful natural chemicals, for example:
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Poisonous mushrooms
Under-processed cassava
Gluten in flour (some people are intolerant to this)
Moulds like aflatoxin, occasionally contaminate stored cereals. Traces of pesticides and herbicides
may remain in foods.
Harmful chemicals form during food processing and cooking . For example acrylamide, which may
increase the risk of cancer, is made in crisp manufacture.
Why do manufactures add chemicals to food?
Additive Type
Purpose of additive
Colourings
To make food look attractive.
Flavourings
To improve taste.
Sweeteners
To make food taste sweeter without adding
sugar.
Emulsifiers
To mix together ingredients that normally
separate.
Preservatives
To prevent harmful microbes growing and to
keep foods safe for longer.
Antioxidants
To prevent fats and oils deteriorating by
reacting with oxygen in the air.
Food additive with E-numbers have passed safety tests. They have been approved for use in the
European Union. Scientific advisory committees do risk assessments to decide on safe levels of
additives.
How can we avoid foods that contain harmful chemicals?
Food labels help consumers decide what to buy and avoid eating harmful chemicals. They give
information about ingredients, including additives and nutrients.
Labels don’t always mention health risks, and may be misleading. For example a food that
‘contains 50% less fat’ but may still have a high fat content.
The UK’s independent food safety watchdog is the Food Standards Agency (FSA). It aims to make
sure that food is safe, healthy and fairly marketed.
How do we digest food?
Enzymes in the digestive system help break down natural polymers into small, soluble compounds.
These small compounds pass through the gut wall and dissolve in the blood. The blood then
transports them around the body.
Big protein molecules break down into smaller amino acid molecules.
Big starch molecules break down into small glucose molecules.
The blood transports amino acid to cells. Cells grow when amino acids join together to make
proteins.
If the body has more amino acids molecules that it needs, it sends them to the liver. The liver
breaks them down into poisonous urea. The blood stream transports urea to the kidneys. The
kidneys remove urea from the blood and excrete it in urine.
What is diabetes?
Glucose is quickly absorbed into the bloodstream, do eating foods high in glucose causes a rapid
rise in blood sugar levels.
In most people, the hormone insulin controls blood sugar levels. The bodies of people with
diabetes do not control blood sugar levels properly .
There are two types of diabetes:

Type 1 – starts suddenly in childhood when immune system cells attack cells in the
pancreas.
The pancreas stops producing enough insulin.
Insulin injections are used to control type 1 diabetes.

Type 2 – usually starts in adulthood and is linked to: poor diet, genetics, obesity, age.
The body stops responding to its own insulin or does not make enough insulin.
Type 2 diabetes can usually be treated with diet and excerise.