Biology Core 1.1 Healthy Living

Biology 1.1 Healthy Living

Microbes and disease

• Microbes need four things to reproduce:

  • Time

  • Warmth

  • Food (oxygen)

  • Moisture

• This makes our bodies perfect hosts for bacteria to grow, which means once inside our body, they can multiply rapidly and make us ill

• Pathogens are microorganisms which can cause infectious disease, and are surrounded by unique molecules called antigens

• Bacteria- are very small cells which can rapidly reproduce by cell division in your body making you feel ill by damaging your body's cells and producing toxins

• Viruses- are NOT cells and much smaller than bacteria and damage the cells in which they reproduce. Viruses replicate by invading a cell and using the cell's genetic machinery to reproduce themselves ie copies of the original virus.The virus 'invaded' cell then bursts releasing lots of new viruses.

• We have many defences which stop pathogens from entering our body and protecting us once they are inside:

  • Skin

  • Tears

  • Nose hairs

  • Mucus in the throat

  • White blood cells

• Antibodies fight the virus whereas antitoxins counteract the toxins released by bacteria which make us feel ill by attacking and damaging our cells

• If a recognised pathogen enters our body, our white blood cells attack it:

  • Phagocytes- Ingest /engulf pathogens

  • Lymphocytes- produces antibodies to destroy the antigen and produces antitoxins that neutralise released toxins

• Having absorbed a pathogen, phagocytes may also send out a chemical message to nearby lymphocytes to identify the type of antibody needed to neutralise them

• After a pathogen has been destroyed by our white blood cells, some cells still remain and ‘remember’ the pathogen, so if it enters again our antibodies will attack the pathogen…