C3 Food Matters- chemicals and elements

Many chemicals in living things are natural polymers such as:

• Carbohydrates, such as cellulose, sugars and starch, are made from the elements carbon, hydrogen and oxygen.
• Proteins are amino acids joined together in long chains. They are mainly made from the elements carbon, hydrogen, oxygen and nitrogen.

Different rhings have different jobs in a cycle:

• Living things take in chemicals by photosynthesis, breathing, absorbtion and eating.
• Decomposers, like microbes and fungi, break down dead plants and animals.
• The 2 processes above recycle the materials in living things.

Farmers use the same land every year to grow crops. When crops grow they take nitrogen, potassium and phosphorus from the ground, in a natural cycle these elements would be replaced when the plants die and decompose, but in farming this doesn't happen, so the ground has less nutrients and the next crop is of poor quality and there's not a lot of it. The farmers need a way to get these elements back into the soil. Intensive and organic farmers use different methods to do this. Pests and diseases also reduce crop yields.

Intensive farmers produce as much food from thier land as possible, they maximise their yeilds by:

• Adding synthetic fertilizers to replace lost 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 intensive farming is unsustainable. Synthetic farmers don' t recycle nutrients. Nitrates from fertilizers may be washed into rivers if misused. Pesticides kill useful animals aswell as animals that damage crops, they also disrupt food chains.

Organic farmers take care to produce food without damaging the environment. They also follow UK national standards. Organic farmers:

• Add manure to soil to replace nutrients,
• Use natural predators to control pests,
• Rotate crops to replace soil nutrients naturally and to reduce crop diseases.

Harmful chemicals in food come from:

• Plants that contain harmful natural chemicals, such as poisonous mushrooms, under-processed cassava, and gluten in flour (which some people are allergic to),
• Moulds like aflatoxin occasionally contaminate stored cereals,
• Traces of pesticides and herbicides that remain in foods,
• Harmful chemicals that form during food processing or cooking,such as acrylamide, which may increase the risk of cancer, is made in crisp manufacture.

Manufacturers add these chemicals to food to do these jobs:

• Colourings- to make food look more attractive,
• Flavourings- to improve taste,
• Sweeteners- to make food taste sweeter without adding sugar,
• Emulsiviers- to mix together ingredients which would normally seperate, such as oil and water,
• Preservatives- to prevent harmful microbes growing and keep food safe for longer,
• Antioxidants- to prevent fats and oils deteriorating (going rancid) by reacting with oxygen in the air.

Food additives with E numbers have passed safety tests. They have been approved for use in the european union. Scientific advisory committees do risk assesments to decide on safe levels of additives.

Food labels help consumers decide what to buy and avoid eating harmful chemicals. They give information about ingredients, including additives and nutrients. But labels do not always mention health risks and may be misleading.

The UK's independant food safety watchdog is the food satandars agency. It sims to make sure that food is safe, healthy, and fairly marketed.

Enzymes in the digestive system break down natural polymers into small soluble compounds, for example, Big protein molecules are broken down into small amino acid molecules and big starch molecules are broken down into small glucose molecules. These pass through the gut wall and disolve in the blood. The blood then transports it round the body.

The blood transport aino acids to cells, and cells grow when amino acids are built up it big proteins. Muscles, tendons, skin, hair and haemoglobins are all mainly made of proteins.

If the body has more amino acids than it needs it sends them to the liver. The liver breaks them down into poisonous urea. The bloodstream transports the urea to the kidneys, the kidneys then remove urea from the blood and excrete it in urine.

Glucose is quickly absorbed into the bloodstream, so eating foods high in glucose cause a rapid rise in blood sugar levels. In most people the hormone insulin controls blood sugar level. The bodies of people with diabetes do not control blood sugar levels properly.

Type 1 diabetes starts suddenly i childhood when immune system cells attack cells in the pancreas. The pancreas stops producing insulin, The patient has to start taking insulin injections.

Glucose is quickly absorbed into the bloodstream, so eating foods high in glucose cause a rapid rise in blood sugar levels. In most people the hormone insulin controls blood sugar level. The bodies of people with diabetes do not control blood sugar levels properly.

Type 2 diabetes ussually starts in adulthood, and is normally linked to poor diet, obesity, genetics and age. The body stops responding to it's own insulin or does not make eough insulin. It is controlled by diet and exercise.