Biology - Keeping healthy

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Diet and exercise

  • 3 main food groups: carbohydrates, proteins and fats
  • Too little food - underweight, too much food - overweight
  • Metabolic rate is the speed at which chemical reactions happen in the body
  • Metabolism is affected by several things including age, gender and genes
  • Also affected by proportion of muscle to fat in the body and amount of exercise
  • Metabolic rate increases as we exercise and stays high for a while after
  • Cholesterol is made in the liver and is needed for healthy cell membranes
  • Too much cholesterol in the blood increases risk of heart disease and diseased arteries

Defending against infection

  • Pathogens are micro-organisms that cause disease
  • Bacteria release toxins and viruses damage cells
  • White blood cells can ingest and destroy pathogens by producing anti-bodies that destroy the infections micro-organisms and antitoxins to neutralise toxins created as a by-product
  • Bacteria are living cells and can multiply rapidly
  • Viruses are much smaller than bacteria
  • They can only reproduce inside host cells and damage the cell when they do this
  • A virus can get inside then take over and make hundreds of thousands of copies of itself
  • Eventually the virus copies fill the host cell causing it to burst open
  • The viruses are then passed out in the bloodstream, the airways or other routes 
  • Pathogens are not…


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