OCR 21st century science, Chemistry C3

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Nitrogen cycle and Farming

Denitrification - The process by which a nitrate turns into moleculer nitrogen by the action of bacteria.

Nitrogen is used in the production protiens and amino acids which are needed for plants and animals to grow. For crop to grow fertile soil is needed.

The Nitrogen cycle - Plants use nitrates to make proteins, When plants get eaten this nitrogen enters the food chain and becomes protein for animals, MOs break down waste products and the proteins in dead animals and plants to form ammonium coumpounds.

Intensive Farmers - aim to produce greater quality foods at cheaper prices, use pasticides to kill pests , use fertilizers which produces higher yeilds, keep animals in a limited space

Organic Farmers - Produce less food at higher prices, use manure for soil, use animals to to scare pesticides away, an organic farm must pass the UK national tests if they want to be recognised as an organic farm(FSA).

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Farming Issues

Farming Issues - When cropd are harvested they remove Nitrogen from the soil so intensive farmers use manufactured fertilizers and organic use manure from animals to replace the nitrogen as it doesnt return from the natural process of decay. Harvested crops also remove Potassium and phosphorus from the soil. Pests may carry dieases and can damage crops so intensive farmers use pesticides and organic farmers use a predator.

Intensive farmers use small land leaving more space for woodland, Hedgerows are often removed to create larger fields to maximise the amount of crops planted each year. The use of pesticides can harm things that are not pests. Pesticides can build up in the food chain passing the toxins further up the food chain.

Organic farmers use less space for farming and less destruction of hedgerows. Food chains dont get affected.Do not use pesticides and fertilizers and use mor local employment. This is more sustainable development.

Eutrophication - A process by which an excess of plant nutrients (eg, nitrogen and phosphorous) reduces the oxygen dissolved within a body of water, producing an environment that does not readily support aquatic life.

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Chemicals in Living Things

Many chemicals in living things are natural polymers e.g. carbohydrates and protiens

Celluse, starch and sugars are carohydrates which contain the element carbon hydrogen and oxygen e.g. Glucose(C6H12O6)

·  Glucose molecules join together in a long chain to form starch:

    • Individual sugar molecules (Glucose) --> Huge, long chains of identical sugar molecules (Starch).
    • Individual sugar molecules (Glucose) --> Long cross-linked chains of sugar molecules (cellulose).
  • Proteins are polymers made from long chains of amino acids. They contain carbon, hydrogen, oxygen, nitrogen and sometimes other elements such as sulphur: Glucose + Nitrates --> Amino acids --> Proteins. 
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Chemicals in food

  • Additives - Something added to a food to improve the food e.g. taste or colour.
  • Chemicals or additives are added to food for a number of reasons:
    • Colouring – Replaces lost colour during processing or storage. Colourful food looks more attractive.
    • Flavouring – Gives a particular taste of flavour. Replaces flavours lost during processing.
    • Emulsifier – Used to mix together ingredients that would normally separate, e.g. oil and water.
    • Stabiliser – Helps to stop ingredients from separating gain.
    • Preservative – Stops mould or bacteria growing in food, so foods are kept safe and fresher for longer.
    • Sweetener – Used to reduce the amount of sugar added to processed foods and drinks.
    • Antioxidant – Added to foods containing fats or oils to stop them from reacting with oxygen in the air.
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The food we eat

Contamination during storage - Moulds growing on cereals, dried fruit and nuts can produce a carcinogen called aflatoxin. 

Use of pesticides and herbicides - the chemicals may still remain in the food we eat.

Food processing/cooking - may produce harmful chemicals

poor storage cooked food - may result in contamination by bacteria, which can lead to food poisioning.

·  Fo

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Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry.

  • There are also a number of ways that people can reduce their exposure to harmful chemicals:
    • Keeping a hygienic kitchen and quickly disposing of waste food.
    • Cooking food properly
    • Not re-freezing previously frozen meats.
    • Regularly cleaning out the fridge to avoid keeping cooked food for too long.
    • Reading food labels – particularly important for people who suffer from coelic disease or have known allergies.

Physical digestion - chewing and squeezing food into smaller pieces so that it can pass more easily through the gut and increases the surface area of the food to help enzymes work more quickly.

Chemical digestion - uses enzymes to break down the large insoluble molecules into smaller soluble molecules.

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Digestion and Diabetes

Diabetes is a disease that is caused by the pancreas not producing and releasing enough insulin, which allows the blood sugar levels to fluctuate (change-rise and fall). This can lead to a person’s blood sugar level rising fatally high, resulting in a coma and even death.

Type 1 -  is when the pancreas stops producing insulin altogether as the special cells in the pancreas are destroyed. This is more likely to start in young people and blood sugar level can be controlled by injecting insulin. Genetic.

Type 2 - is when the pancreas does not make enough insulin or the cells do not respond as the insulin made by the pancreas is resistant to the body or it is too weak (not enough to help glucose absorb into the bloodstream. This can often be treated by diet and exercise (although medicine and insulin injections are also needed). Environmental.

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dan nad


Doesn't have everything, however it is still useful.

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