Topic 5: Health and Disease

• Health (WHO) - a state of complete physical, mental and social well being and not merely the absence of disease or infirmity
• Communicable Disease - a disease that can be passed from one person to another
• Non Communicable Disease - a disease that cannot be passed from one person to another
• If affected by one disease, it makes a person more susceptible to others as the immune system is weakened
• Pathogens - organisms that cause communicable diseases such as viruses, bacteria, fungi and protists
• Common Infections:

  • Cholera (bacterium) - causes diarrhoea by contaminated water
  • Tuberculosis (bacterium) - causes coughing/lung damage by air
  • Chalara Ash Dieback (fungus) - causes leaf loss/bark lesions by air
  • Malaria (protist) - damages red blood cells by mosquitos as vectors
  • Stomach Ulcers (bacterium) - causes stomach pain/nausea/vomiting by oral transmission like eating contaminated food
  • Ebola (virus) - causes haemorrhagic fever by bodily fluids
• Lytic Virus Lifecycle:

  1. Virus injects genetic material into a specific host cell
  2. Proteins and enzymes inside the host are used to replicate the genetic material
  3. New viruses are created inside and the host cell bursts open to release them
• Lysogenic Virus Lifecycle:

  1. Virus injects genetic material into a specific host cell
  2. Genetic material merges with the host cell genome so that when the host divides, the virus also multiplies
  3. Virus DNA remains dormant until it is triggered into the lytic pathway
• STIs are infections spread by sexual contact and can usually be prevented using barrier contraception methods:

  • Chlamydia (bacteria) - causes infertility and can be reduced by screening, barrier methods and avoiding sexual contact
  • HIV (virus) - kills white blood cells so the immune system weakens, leading to AIDS which can be prevented by reducing body fluid contact (condoms/not sharing needles) and medication
• Plant Physical Barriers:

  • leaves/stems have a waxy cuticle to stop pathogens entering via water collection and pests damaging them
  • cell walls made of cellulose stop pathogens past the cuticle
• Plant Chemical Barriers:

  • antiseptics kill pathogens
  • smells deter pests from feeding off leaves
  • some chemicals are used as drugs in human medicine
• Field Plant Diseases:

  • plant pathologists recognise symptoms of disease and investigate the environmental conditions like nutrient deficiency
  • distribution of diseased plants can help identify pathogen or environmental change
  • patches suggest pathogen is in soil while a more random distribution suggests an airborne pathogen
• Lab Plant Diseases:

  • pathogens have unique antigens which can be detected in an infected plant tissue sample using monoclonal antibodies
  • pathogen DNA can be detected in small amounts
  • accurate identification and diagnostic of disease
• Human Physical Barriers:

  • skin blocks pathogens and blood clots cover wounds
  • mucus traps particles that may contain pathogens
  • cilia are found in the trachea/bronchi and move mucus to the back of the throat where pathogens can be swallowed
• Human Chemical Barriers:

  • hydrochloric acid in the stomach kills swallowed pathogens
  • lysozyme is found in tears and kills bacteria on the eye surface
• B-Lymphocytes:

  • create antibodies for specific pathogen antigens
  • antibodies bind onto antigens to kill the pathogen
  • produced rapidly

  Memory Lymphocytes - remain in the body to remember a specific antigen so the body is ready to combat it again
• Immunity:

  • first exposure to a pathogen means the immune system is slow as there are no b-lymphocytes to create the specific antibodies immediately
  • secondary immune response is faster as the memory lymphocytes cause the b-lymphocytes to produce antibodies to kill pathogens before symptoms are shown
• Immunisation - injecting dead or inactive antigenic pathogens into the body to trigger memory lymphocytes without harming the person so they can immediately have a secondary immune response
• Immunisation Pros (+) and Cons (-):

  • herd immunity prevents epidemics (large immunised percentage means less can pass it on) +
  • immunisation programmes have wiped out some diseases (small pox) +
  • doesn't always give immunity -
  • bad reactions to vaccines are possible -
• Antibiotics inhibit processes like building bacterial cell walls in bacterial cells but not the host organism meaning viruses are unaffected as they use host cells to multiply
• Aseptic Techniques:

  • sterilise petri dishes and growth mediums using an autoclave (steam at high temperature/pressure)
  • sterilise inoculating loops by passing it through a hot flame
  • keep liquid bacterial cultures in a culture vial with a lid
  • cover petri dish with a lightly taped on lid
  • store petri dish upside down to stop condensation on agar
• Antibiotics Practical:

  1. Place paper disks soaked in different antibiotics onto an agar plate with an even covering of bacteria
  2. A clear area called the inhibition zone will form depending on how many bacteria are killed (the more effective the larger the area)
  3. Use a paper disk not soaked in anything as control
  4. Leave for two days at 25'C
• Stages of Developing Drugs:

  1. Preclinical testing means drugs are used on human tissue and cells
  2. Live animal testing shows how effective the drug is for its intended purpose, how toxic it is and estimate the best dosage
  3. Clinical testing means that healthy human volunteers are used to check for any harmful side effects
  4. Opium dose is then found on ill patients of multiple ages, sexes ext.
  5. Drug must be approved by a medical agency before mass production
• Monoclonal Antibodies:

  1. A mouse is injected by an antigen which causes the b-lymphocytes to produce many antibodies and fast dividing tumour cells are grown
  2. The mouse b-lymphocytes are combined with the lab tumour cells to create a hybridoma
  3. Hybridoma cell can divide quickly to create many monoclonal antibodies that can be modified to bind to anything
• Pregnancy tests use monoclonal antibodies to detect the presence of the hormone HCG using chromatography:

  • Positive - hormone in pee binds to antibodies with blue beads meaning strip remains blue
  • Negative - antibodies don't have the hormone to stick to the strip with so strip remains clear as pee moves antibodies up
• Monoclonal Antibodies and Cancer:

  • monoclonal antibodies can bind to tumour markers
  • radioactive elements can be attached meaning areas of high radioactivity will show where cancer cells are
  • anti-cancer drugs can also be attached to kill cancer cells (will not harm normal cells)
  • safer and less side effects than radiotherapy
• Monoclonal antibodies can bind to the proteins that make up blood clots meaning radioactive elements can be attached to find any potentially harmful blood clots in the body
• Risk Factors - things linked to the increase in the likelihood that a person will develop a certain disease during their lifetime
• Non-Communicable Diseases:

  • diet with unbalanced nutrients leads to malnutrition (scurvy is vitamin C deficiency)
  • little exercise and a high fat/sugar diet leads to obesity
  • alcohol leads to liver disease which can permanently scar liver (cirrhosis)
  • smoking damages arteries and builds up fats which leads to cardiovascular disease and strokes
• Cardiovascular Disease Treatments:

  • eat a healthy balanced diet and do regular exercise
  • take lifelong medicine (statins reduce cholesterol, anticoagulants prevent blood clots, antihypertensives reduce blood pressure)
  • surgical procedures (stents keep arteries open, coronary bypass surgery, donor heart which may be rejected)