This is the chemical reaction which allows cells to release energy from food.
The metabolic rate
This is the speed at which chemical reactions take place in the body; this varies due to several factors:
- Inherited factors
These are microorganisms such as bacteria or viruses which cause disease.
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.
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.
Diseases caused by bacteria
- Food poisoning
- Whooping cough
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.
Diseases caused by viruses
- Chicken pox
Antibodies are proteins which can neutralise pathogens in a number of ways.
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.
These are effective against bacteria; they can kill bacteria or stop their growth. They do not work against viruses as they reproduce within cells.
Painkillers help to relieve the symptoms of an infectious disease, however they do not kill the pathogens involved.
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.
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.
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
These are substances that change chemical reactions in the body.
These are used to relieve disease and illness and are extensively tested before being used.
These are taken by people because they like the effect it has on their body e.g. alcohol and tobacco. These may be addictive.
Illegal recreational drugs
Cannabis and heroin are examples of these and they are very addictive and can be dangerous
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
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.
This happens when light is the stimulus of a plant. The leaves response is positive whereas the roots response is negative.
This happens when gravity is the stimulus of a plant. The leaves response is negative, whereas the roots response is positive.