Chemicals and elements
All living things are made of chemicals.
There is a continual cycling of elements in the environment.
The nitrogen cycle is and example of a natural cycle.
Where crops are harvested elements, such as nitrogen, pottasium, and phosphorus, are lost from the soil.
Land becomes less fertile unless these elements are replaced.
Organic and intensive farmers use different methods to keep soil fertile for growing crops.
Organic and intensive farmers use different methods to protect crops against pests and diseases.
Farming and chemicals
Farmers have to follow the UK national standards if they want to claim that their products are organic.
Farming has an impact on the natural environment.
Some methods of farming are more sustainable than others.
Some natural chemicals in plants that we eat may be toxic if they are not cooked properly, or they may cause allergies in some people.
Moulds that contaminate foods during storage (such as aflatoxin in nutsand cereals) may add toxic chemicals to food.
Chemicals used in farming (such as pesticides and herbicides) may be in the products we eat and may be harmful.
Harmful chemicals may be produced during food processing and cooking.
Natural and synthetic polymers may be added to food during processing:
- Food colours can be used to make processed food look more attractive.
- Flavourings enhance the taste of the food.
- Artificial sweeteners help to reduce the amount of sugar in processed foods and drinks.
- Emulsifiers and stabilizers help to mix together ingredients that would normally seperate, such as oil and water.
- Preservatives help to keep food safe for longer by stopping the grwth of harrmful microbes.
- Antioxidants are added to foods containing fats or oils to stop them reacting with oxygen in the air.
Many chemicals in living things are natural polymers (including carbohydrates and proteins)
Cellulose, starch and sugars are carbohydrates that are made up of carbon, hydrogen and oxygen.
molecules and digestion
Amino acids and proteins consist mainly of carbon, hydrogen, oxygen and nitrogen.
Digestion breaks down natural polymersto smaller, soluble compounds (for example digestion breaks down starch to glucose and proteins to amino acids).
These small molecules can be absorbed and transported in the blood.
Cells grow by building up amino acids from the blood into new proteins.
Excess amino acids are broken down in the liver to the urea, which is excreted by the kidneys in urine.
High levels of sugar, common in some processed foods, are quickly absorbed into the blood stream, causing a rapid rise in the blood sugar level.
There are two types of diabetes (type 1 and type 2).
Late-onset diabetes (type 2) is more likely to be triggered by a poor diet.
Obesity is one of the risk factors for type 2 diabetes.
In type 1 diabetes the pacreas stops producing enough of the hormone, insulin.
In type 2 diabetes the body no longer responds to it's own insulin or does not make enough insulin.
Type 1 diabetes is controlled by insulin injections and type 2 diabetes is controlled by diet and exercise.