AQA GCSE Biology B1.1 Keeping healthy

Diet and exercise
1. A healthy diet has a balance of food types: Carbohydrates, fats & proteins,
  1. They are used to release energy and build cells.
  2. Also need vitamins and minerals in small amounts for healthy funtioning of the body.
  3. A person becomes malnourished if their diet becomes unbalanced; this can be by either taking in too little energy or too much
2. Energy in = energy used ~ no mass gain
  1. Energy in > energy used ~ mass gain
    1. Energy in < energy used ~ mass loss
      1. Taking in too much energy can lead to obesity
        Obesity can cause severe health problems such as type 2 diabetes.
3. The more you exercise the more energy you use
  1. Exercise also increases the metabolic rate.
    1. The metabolic rate is the speed in which chemical reactions take place in the body, particularly in cellular respiration
    2. The proportion of muscle to fat in your body & inherited factors can also increase your metabolic rate.
4. Cholesterol is needed for your cell membranes and to make vital substances.
  1. Cholesterol is inherited and having bad cholesterol can lead to heart disease.
Pathogens and disease
1. Micro-organisms which cause infectious diseases are called pathogens.
  1. Bacteria and viruses reproduce rapidly inside your body and produce toxins (poisons) which make you feel ill
    1. Bacteria are LARGER than viruses.
      1. Viruses reproduce inside the cells in your body, which damages your cells and makes you feel ill. Because they reproduce inside your cell, it means that they cannot be treated with antibiotics as any treatment would also damage the cell.
        Painkillers such as ibuprofen can alleviate symptoms but not kill the pathogen.
        The immune system will eventually overcome the viral pathogen.
    2. White blood cells help to defend us against pathogens by:
      1. Producing antitoxins, which counteracts the toxins produced by pathogens
        Producing antibodies, which destroy particular bacteria or viruses with the right antigens
        Producing phagocytes which engulf and ingest pathogens
    3. Antibiotics are medicines which help cure bacterial disease by killing infectious bacteria inside the body.
      1. Specific bacteria should be treated with specific antibiotics
      2. They have greatly reduced the number of deaths due to bacterial infections.
      3. Misuse and overuse of antibiotics has increased the rate of development of antibiotic resistant strains of bacteria.
        Many strains of bacteria, such as MRSA (Methiicillin resistant staphylococcus aureus), have developed a resistance to antibiotics as a result of natural selection.
      4. Mutations of pathogens produce new strains and so vaccinations and antibiotics may not be effective against the new strain of pathogen. The strain will then spread rapidly because there is no treatment.
      5. Antibiotics kill individual bacterial pathogens of the non resistant strain.
        Individual resistant pathogens survive and reproduce, so the population of the resistant strain increases.
        Now. antibiotics are not used to treat non-serious infections so the rate of development of resistant strains of bacteria slows down.
2. Semmelweiss recognized the importance of hand washing in the prevention of spreading infectious diseases. By insisting doctors washed their hands before examining their patients he greatly reduced the number of deaths due to infectious diseases in his hospital.
  1. However, it did take a long time for people to accept his ideas as no one knew about viruses and bacteria then,.
3. Diseases which spread within a country result in a epidemics whilst ones which spread across countries result in a pandemic.
4. Vaccinations
  1. Dead or inactive (attenuated) forms of bacteria are injected into the body.
    1. This is called a vaccine
      1. The vaccine stimulates the white blood cells to produce antibodies that can kill the pathogen.
        This makes the person immune to further infections by the microorganism.
        If the body came into contact with the same bacteria again, it would respond by rapidly producing the correct antibody in the same way as if the person had previously had the disease.
        This works because the antibodies produced by the white blood cell would recognize the antigen (protein shape) on the pathogen.
  2. The MMR vaccine is is one of several vaccinations. It is used to prevent mumps, measles and rubella in children.
Growing and investigating bacteria
1. Pure cultures of non-pathogenic bacteria can be used in lab investigations.
  1. A culture of microorganisms can be used to find the effect of antibiotics on bacteria.
    1. For this:
      1. Petridishes and culture media must be sterilised before use to kill unwanted microorganisms
        Inoculating loops used to transfer microorganisms must be sterilised by being passed through a flame.
        The lid of the petri dish must be sealed with tape to prevent any unwanted microorganisms entering from the air.
        A culture medium such as agar jelly should be used to provide nutrients.
    2. In school and college labs they must be incubated at a maximum temperature of 25 degrees C, which greatly reduces the chance that the pathogens that grow would be harmful to humans.
      1. In industrial conditions higher temperatures can be used for more rapid growth.

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AQA GCSE Biology B1.1 Keeping healthy

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