Biology - Keeping Healthy

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Diet and Exercise

Diet and Excercise

Healthy diet contains the right balance of foods your body needs and provides the right amount of energy. Carbohydrates, fats and protiens are used by the body to release energy and to build cells. Mineral ions and vitamins are needed in small amounts for the body to function correctly.

A person who doesn't have a balanced diet is malnourished. A poor diet can lead to:

  • a person being overweight or obese
  • a person being underweight
  • deficiency diseases or conditions such as type 2 diabetes.

Body mass is lost when the amount of energy in food is less than the amounts of energy being used by their body. Excercise increases the amount of energy used by the body. Inherited factors affect health:

  • metabolic rate
  • Cholesterol level
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Metabolic Rate and Cholesterol

Metabolic Rate

Metabolic rate is the rate at which all the chemical reactions in your body's cells are carried out. It is affected by:

  • the amount of activity or exercise you do
  • the proportion of fat to muscle
  • inherited factors


Cholesterol is made in your liver and is found in your blood. It is also found in some foods. The amount of cholesterol in your blood depends on:

  • your diet
  • inherited factors

Too much cholesterol in the blood can increase the risk of heart diseases.

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Defence Against Infectious Diseases

Defence against infectious diseases

Microorganisms that cause infectious diseases are called pathogens. 2 main types are:

  • bacteria
  • viruses

White blood cells defend againt pathogens by:

  • ingesting pathogens
  • producing antitoxins to neutralise toxins from pathogens
  • producing antibodies to destroy particular pathogens

Bacteria                                                                Viruses

  • are very small                                          are smaller than bacteria
  • reproduce rapidly                    reproduce rapidly once inside living cells, damaging them
  • may produce toxins to make you feel ill     may produce toxins to make you feel ill
  • cause illnesses like cholera     cause illnesses like colds, flu, measeles and polio.        and tuberculosis



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Immunity and Vaccinations

Immunity and Vaccinations

When white blood cells produce specific antibodies to kill a pathogen it leads to immunity from that pathogen. Whiteblood cells are sensitised to that particular pathogen and can produce antibodies quick if it infects again.

You can acquire immunity to a particular disease by being vaccinated (immunised):

  • a small amound of inactive pathogen is injected into your body
  • your white blood cells produce antibodies to destroy the patogen
  • you then have the acquired immunity to this particual pathogen becuase your white blood cells are sensitised to it.

For example of a vaccine is the MMR vaccine used to protect children from measles, mumps and rubella. If a large proportion the the population is vaccined then the pathogen spreads far less easily.

Semmelweiss was a doctor who worked in hospitals in the 1840s and recognised how good hygiene of washing hands prevents infectious diseases reducing the number of deaths.





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Diagrams - Defence


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Diagram - Vaccination


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