Keeping Healthy

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Diet and Exercise + Weight Problems

A healthy diet has the right balance of food groups. Cabohydrates, fats and protein are used by the body to release energy and build cells.

Mineral ions and vitamins are needed to keep the body healthy. If someone has an unbalanced diet they may become malnourished.

If you excersise more energy is used by the body, this increases your metabolic rate. This means that the chemical reactions in cells will work faster. The proportion of musclue to fat in your body and inherited factors can also affect this.

If the energy you take in is equal to the energy you use then your mass will stay the same. Eating too much foos can lead to you becoming obese and overweight.

Long term obesity can lead to many severe health problems, one of them being type 2 diabetes. This is when you have high blood sugar.

You can also become unhealthy by eating too little food. You will find it hard to walk and could suffer from defficiency diseases due to the lack of vitamins or minerals.

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Cholesterol, Salt and Other Factors

There are two types of cholesterol. 'Good' cholesterol (HDL) is an important part of cell membranes. However 'Bad' cholesterol (LDL) can lead to problems such as heart disease. 

Cholesterol is a major cause of heart disease because it causes inflamation on your blood vessels. It is carried around the body by blood.

Saturated fats are found in foods such as: Meat, dairy and sugar. Unsaturated fats are found in foos such as: Oily fish, seeds, sunflower and olive oils.


Salt is important for your digestive system to work. However, high levels of salt in your diet can cause high blood pressure.

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Pathogens + Disease and Defence Mechanisms

Pathogens can cause infectious diseases, they are tiny microoorganisms - ususally bacteria or viruses. When bacteria  or viruses enter your body they reproduce rapidly. They can make you feel ill by producing toxins.

Viruses are much smaller than bacteria and reproduce inside youb cells, the damage to these cells can also make you ill.

Before bacteria and viruses had been discovered a famous doctor called Semmelweiss realised that infection could be transferred from person to person in a hospital because of unwashed hands.

This skin prevenyts pathogens from getting into the body, they are also trapped by mucus and killed by stomach acid. 

White blood cells are part of the immune system. They do three things to defend the body:

  • They ingest pathogens. This means they digest and destroy them. 
  • They produce antibodies to help destroy particular pathogens.
  • They produce antitoxins to counteract the toxcins that pathogens produce.
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Growing and Investigating Bacteria

Pure cultures of non-pathogenic bacteria can be used for lab investigations. A culture of microorganisms can be used to find the effect of antibiotics on bacteria.Investigations need uncontaminated cultures of microorganisms. Contamination might come from your skin, the soil, air or water which is around you. If the culture becomes contaminated other bacteria could grow, including pathogens.

Growing Cultures

To grow microorganisms in a lab you must:

  • Give them a liquid or gel containing nutrients, this is know as a culture medium. A culture medium called agar jelly is used.
  • Provide warmth and oxygen.
  • Keep them incubated at 25 degrees celsius in school labs.

To keep the culture pure you must:

  • Kill all bacteria on equipment. Pass metal loop through a flame, boil solutions and agar.
  • Seal dish to keep air from getting into the equipment.
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Immunity and Vaccines + Antibiotics


Dead or inactive forms of a athogen are used to make a vaccine, these are injected into the body.

The white blood cells react by producing antibodies, this makes the person immune. It prevents further infection because the body responds quickly by producing more antibodies. The antibodies recognise the antigen on the pathogen.

An example of a vaccine is MMR, this is given to prevent measles, mumps and rubella.

Antibiotics will kill infective bacteria in your body. Penicillin is a form of antibiotic, it was discovered by Alexander Fleming in 1928.

Viruses are hard to destroy because they reproduce inside the body cell, so any treatment given could also damage the cells.

Painkillers and other drugs help relieve pain or symptoms, but do not kill the pathogen.

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Antibiotic Resistance

An antibiotic is a chemical that kills bacteria but not viruses. It destroys the cell walls of the bacteria, but does not affect the human body cells. 

Because viruses are inside cells, they are not affected. If a bacteria mutates it becomes resistant to antibiotics. A mutation is a changein the DNA of an organism, which can change a characteristic.

Some bacteria have mutated and become resistant to one or more antibiotics.

The MRSA 'super bug' is a bacterium which has evolved through natural selection. It is now resistant to the common antibiotics.

Antibiotics kill individual pathogens of the non-resistant strain. the resistant bacteria survive and reproduce and a whole population of a resistant strain develops. Antibiotics should not be used for mild infections, in order to slowdown the rate of development of resistant strains.

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What do we mean by a 'balanced diet'?

Give three reasons to why a person may be malnourished.

What is meant by 'metabolic rate' and what factors affect the rate?

What is a pathogen and and antibiotic?

Why is it difficult to produce medicines which destroy viruses?

How are the ideas of Semmelweiss used in modern hospitals?

What is meant by a mutation of a pathogen?

Why don't doctors give antibiotics for mild throat infections?

Explain how bacteria develop antibiotic resistance.

How does a person develop immunity following vaccination?

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