Biology unit 1
- Created by: jessieclaire
- Created on: 21-04-14 18:05
Respiration
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:
- Age
- Gender
- Inherited factors
Pathogens
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
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
- Cholera
- Typhoid
- Whooping cough
Viruses
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
- Colds
- Mumps
- Measles
- Rubella
- Chicken pox
- Influenza
Antibodies
Antibodies are proteins which can neutralise pathogens in a number of ways.
Vaccination
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.
Antibiotics
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
Painkillers help to relieve the symptoms of an infectious disease, however they do not kill the pathogens involved.
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.
Receptors
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.
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
Drugs
These are substances that change chemical reactions in the body.
Medical drugs
These are used to relieve disease and illness and are extensively tested before being used.
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.
Illegal recreational drugs
Cannabis and heroin are examples of these and they are very addictive and can be dangerous
Alcohol
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
Nicotine
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.
Phototropism
This happens when light is the stimulus of a plant. The leaves response is positive whereas the roots response is negative.
Gravitropism
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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