UNIT 3 BIOLOGY

• Communicable diseases to learn


  • Cholera
  • Cold/flu
  • Salmonella (food poisoning)
  • Malaria
  • HIV
  • Gonorrhoea
  • Athlete's foot
  • Measles
• Cholera


  Caused by bacteria, spread by contaminated water
• Cold/flu

  Caused by virus, spread by air droplets
• Salmonella (food poisoning)


  Caused by bacteria, spread by contaminated food, symptoms: fever, vomiting, diarrhoea, stomach pain
• Malaria


  Caused by protist, spread by mosquitos
• HIV


  Caused by virus, spread by sexual contact, symptoms: flu-like symptoms, weakened immune system, leads to AIDS
• Gonorrhoea


  Caused by bacteria, spread by sexual contact, symptoms: thick yellow/green discharge, pain urinating
• Athlete's foot


  Caused by fungus, spread by contact
• Measles


  Caused by virus, spread by air droplets, symptoms: fever, red skin rash
• How the body stops pathogens from entering the blood


  1. Mucus – found in trachea (wind pipe); pathogen stick to it

  2. Cilia – found in trachea; tiny hairs that sweep out the mucus that contains pathogens

  3. Stomach acid – kills pathogens that enter via our food

  4. Skin – barrier; produces antimicrobial secretions

  5. Nose hairs – catch larger particles
• If pathogens DO enter the blood, bacteria produce toxins, which make us feel unwell
• If pathogens DO enter the blood, viruses invade and destroy our own cells
• White blood cells


  • Lymphocytes produce antibodies, which stick to the pathogens and stop them from moving
  • Lymphocytes produce antitoxins, which neutralise the toxins made by bacteria
  • Phagocytes engulf (swallow) pathogen = phagocytosis
• Medicines and medical technology to protect us from diseases


  • Vaccination: weakened/dead version of the pathogen is injected; white blood cells are stimulated to produce the right antibody; they remember how to do this is this pathogen ever infects the blood; they can destroy the pathogen before the person becomes ill
  • Antibiotics: kill bacteria (but bacteria can become resistant if antibiotics are overused, or if the course of antibiotics is not finished) – good hygiene and painkillers should be used to stop the spread of bacteria and treat the symptoms of the illness instead of using antibiotics if possible
  • Painkillers – treat the symptoms of the illness (make you feel better) but do not kill the pathogen – it allows you to feel well enough to let your body fight the pathogen itself
  • Genetic modification: remove a gene from the DNA of one organism, make many copies of that gene by inserting it into a vector, insert the gene into the DNA of another organism using enzymes (can be used to make bacteria produce human insulin, grow human tissues for transplants in pigs and make sheep produce human proteins in their milk)
  • Stem cells (undifferentiated cells( can be used to treat heart disease and type 1 diabetes as we can grow tissues from them: Adult stem cells (from bone marrow) can differentiate to make a few types of cells, Embryonic stem cells (from embryos) can differentiate to become ANY type of cell, but embryos are destroyed in the process, Stem cells are also found in umbilical cords
• Drug development


  1. Tested for toxicity, efficacy and dosage in a lab using cells, tissues and animals

  2. Clinical trials on healthy volunteers and patients using a double-blind method where patients are randomly given the new drug or a placebo and neither patients nor doctors know who has which

  3. The drug is peer-reviewed to prevent false claims
• Health


  A physical state of mental and social well-being
• Disease


  Something that stops the body from working properly, causing symptoms
• Communicable disease


  Caused by pathogens (microorganisms)
• Homeostasis


  The regulation of the internal conditions of an organism (e.g. blood glucose, water levels and temperature)
• Pathogen


  A microorganism that spreads disease
• Coronary heart disease (CHD)

  Fatty material builds up in the coronary arteries due to high cholesterol, reducing blood flow to the heart so the heart receives less oxygen and glucose, leading to the heart muscle dying (heart attack)
• Treatments for CHD


  • Stent: wire tube used to hold the artery open
  • Statins: drugs that lower cholesterol and slow down the build-up of fatty deposits
• Treatments for other heart problems


  • Replacing faulty valves with biological or mechanical valves
  • Artificial hearts can be used to keep patients alive while waiting for a transplant
• CHD is a non-communicable disease – the risk of it is increased by smoking, obesity, high cholesterol diet and lack of exercise
• Types of diabetes


  • TYPE 1: Body doesn't produce insulin, treated by injecting insulin, born with it
  • TYPE 2: The body's cells don't respond to insulin, managed with exercise and a low sugar/carbohydrate diet, caused by high sugar/carbohydrate diet and lack of exercise
• Diabetes is a non-communicable disease where the sufferer's blood sugar levels become too high
• Controlling blood glucose (an example of homeostasis)


  1. High sugar/carb diet leads to an increase in blood glucose

  2. This is detected by the pancreas

  3. The pancreas releases the hormone insulin

  4. Insulin travels in the blood and tells cells to absorb glucose from the blood

  5. The liver and muscle cells convert the glucose into glycogen to store it
• If blood glucose levels get too low (following exercise or low sugar/carb diet), the pancreas releases glucagon, which stimulates cells to release glucose into the blood (muscle and liver cells will break down glycogen to release more glucose)
• Reproductive hormones


  • Oestrogen is the main female reproductive hormone, produced in the ovaries
  • The release of an egg in the female reproductive system is called ovulation – it happens around day 14 of the 28 day menstrual cycle
  • FSH (released by the pituitary gland) causes maturation of the egg in the ovary and stimulates the production of oestrogen
  • LH (released by the pituitary gland) stimulates the release of the egg
  • Oestrogen (inhibits FHS; stimulates LH) and progesterone (inhibits LH and FSH) are involved in maintaining the uterus lining
  • Contraceptive pills contain oestrogen and progesterone and they inhibit egg maturation
  • Fertility treatments include FSH and LH which causes several eggs to mature and be released, for use in IVF
  • Testosterone is the main male reproductive hormones – it is made in the testes and stimulates sperm production