Biology unit 1

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This is the chemical reaction which allows cells to release energy from food.

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The metabolic rate

This is the speed at which chemical reactions take place in the body; this varies due to several factors:

  • Age
  • Gender
  • Inherited factors
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These are microorganisms such as bacteria or viruses which cause disease.

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White blood cells

These can ingest and destroy pathogens by producing antibodies to destroy the infecious microorganism and also release antitoxins to neutralise any toxins created as a by product.

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Bacteria are living cells which can multiply rapidly in the right conditions. Once inside the body they release poisons or toxins which can make us feel ill. 

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Diseases caused by bacteria

  • Food poisoning
  • Cholera
  • Typhoid
  • Whooping cough
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Viruses can only reproduce inside a host cell. They damage cells when they do this. When the virus gets inside a cell it produces hundreds of copies of itself which eventually causes the host cell to burst open. The viruses then pass through the bloodstream, the airways ect.

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Diseases caused by viruses

  • Colds
  • Mumps
  • Measles
  • Rubella
  • Chicken pox
  • Influenza
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Antibodies are proteins which can neutralise pathogens in a number of ways.

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Vaccination causes the body to produce enough white blood cells to be able to defend itself against a pathogen. Different vaccinations are needed for different pathogens.  

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These are effective against bacteria; they can kill bacteria or stop their growth. They do not work against viruses as they reproduce within cells.

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Painkillers help to relieve the symptoms of an infectious disease, however they do not kill the pathogens involved.

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Antibiotic resistance

Bacteria strains can develop resistance to antibiotics. This happens due to natural selection. In a large population of bacteria, some may not be affected by the antibiotic. These bacteria then reproduce, producing even more bacteria which are not affected by the antibiotics.

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These are a group of specialised cells that can detect changes in the environment called stimuli. Each receptor organ has receptors for a particular stimulus. e.g. ears and sound.

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Reflex actions

Sometimes a very quick response is needed  when the receptor sends a signal to the brain:

  • A muscle contracting
  • Eyes scrunch  up when you look at the sun
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These are substances that change chemical reactions in the body.

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Medical drugs

These are used to relieve disease and illness and are extensively tested before being used.

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Recreational drugs

These are taken by people because they like the effect it has on their body e.g. alcohol and tobacco. These may be addictive.

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Illegal recreational drugs

Cannabis and heroin are examples of these and they are very addictive and can be dangerous

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This is a depressant, meaning it slows down the signals in the nerves and the brain. Great amounts of alcohol can lead to a lack of self - control. Alcohol is an addictive substance. Long term damage it can cause includes:

  • Damage to the liver
  • Damage to the brain
  • Weight gain
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This is an addictive substance in tobacco smoke. It reaches th brain within 20 seconds and creates a dependancy so that smokers become addicted. Smoking can increase the risk of:

  • Heart disease and strokes
  • Miscarriage, premature birth and low birth weight
  • Lung cancer, mouth cancre and throat cancer.
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This happens when light is the stimulus of a plant. The leaves response is positive whereas the roots response is negative.

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This happens when gravity is the stimulus of a plant. The leaves response is negative, whereas the roots response is positive.

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