INFECTION AND RESPONSE

• Pathogens are disease-causing microorganisms that harm our cells by producing poisons/toxins
• There are four types of pathogens: viruses, bacteria, fungi, and protists
• Viruses need a host cell to survive and multiply rapidly within body cells
• Bacteria reproduce rapidly through binary fission inside the body
• Diseases can be transmitted through various ways:

  • Airborne/through droplets
  • Food/waterborne
  • Direct contact
  • Indirect contact
  • Vector-borne (e.g. mosquitoes)
  • Sharing bodily fluids
• Prevention methods for disease spread include:

  • Isolation
  • Clean, sterile water
  • Vaccinations
  • Good hygiene
  • Barrier contraception
  • Targeting vectors
• Bacterial diseases:

  • Gonorrhoea: spread by direct sexual contact and bodily fluids, treated with antibiotics and prevented with barrier contraception
  • Salmonella: foodborne, treated with antibiotics in severe cases, prevented with vaccinated chickens, good kitchen hygiene, and fully cooked food
• Viral diseases:

  • HIV: spread by bodily fluids, controlled with antiretrovirals, prevented by barrier contraception or avoiding sharing bodily fluids
  • Tobacco Mosaic virus: in plants, spread by direct contact, no treatment but prevented with good field hygiene and resistant crop strains
  • Measles: spread by inhalation of droplets, no treatment but prevented with vaccinations and isolation
• Fungal diseases:

  • Rose Black Spot: in plants, spread by air or water, treated with fungicides, prevented by removing and burning infected leaves
• Protist diseases:

  • Malaria: spread by mosquito vector, treated with drugs, prevented by controlling mosquito populations
• Primary defenses of the body against pathogens:

  • Eyes produce antiseptic tears
  • Skin creates a physical barrier and produces sebum
  • Nose hairs and mucus trap pathogens
  • Goblet cells produce mucus in the trachea
  • Stomach contains hydrochloric acid
• Immune system defenses:

  • Made up of white blood cells, phagocytes, and lymphocytes
  • Lymphocytes produce antibodies and antitoxins
  • Phagocytes perform phagocytosis
  • Vaccinations trigger B-lymphocytes to produce antibodies
• Antibiotic resistance:

  • Bacteria become resistant to antibiotics
  • Caused by overprescription, wrong prescription, not finishing full course, or overuse in agriculture
• Testing efficacy of antibiotics:

  • Use aseptic techniques
  • Independent variable: type of antibiotic discs
  • Dependent variable: size of inhibition zone
  • Control: spreading bacteria evenly and using a paper disc
• Monoclonal antibodies:

  • Created by injecting antigen into a mouse
  • Lymphocytes produce specific antibodies
  • Fused with tumour cell to form hybridoma
  • Used in pregnancy tests, diagnosis, and treatment of diseases
• Plant diseases:

  • Identified by stunted growth, spots on leaves, rot/decay, discolouration, malformed stems/leaves, or pests
  • Defended by physical, mechanical, and chemical defenses
• Mineral deficiencies in plants:

  • Nitrates deficiency: weak stem, dead lower leaves, pale green upper leaves
  • Magnesium deficiency: yellow/pale green leaves due to chlorosis
• Plants have different defenses:

  • Physical: cellulose cell wall, waxy cuticle, bark
  • Mechanical: thorns/hairs, mimicry
  • Chemical: antibacterial/antimicrobial chemicals, poisons
• MONOCLONAL ANTIBODY PROS- treat range of conditions, big potential for improvement, do not affect healthy cells due to specific bonding
• MONOCLONAL ANTIBODY CONS- cause major side effects, expensive and difficult to produce
• REQUIRED PRACTICAL ON ASEPTIC TECHNIQUES:

  • Wash hands with soap and water
  • Clean and sterilise the bench
  • Sterilise glass spreader in ethanol
  • Open the bacterial culture and flame the lid with a bunsen burner
  • Label the agar dish
  • With a disposable pipette put the bacterial culture on the agar plate but don’t fully open the lid
  • Spread the bacteria with the glass spreader
  • Store inverted at 37 degrees celsius for a week
  • Measure the area of thc circles
• Digitalitis is a drug that originates from the foxglove plant and can protect against heart disease/high blood pressure
• A painkiller is a drug taken to alleviate pain/symptoms that does not kill the pathogens
• Aspirin is a painkiller that originates from willow tree bark and has anti-inflammatory and pain relief properties
• Penicillin is an antibiotic discovered by Alexander Flemming that originates from penicillium mould and is effective against bacteria
• MRSA is a bug resistant to most antibiotics that is mostly found in hospitals
• The best defence against MRSA is hygiene
• Stages of drug development:

  • Pre-clinical trials are done on clumps of cells or animals such as mice/rabbits to test for efficacy, safety, and toxicity
  • Testing on healthy volunteers in small doses to test for safety
  • Double blind trials are conducted, where one of the drugs is a placebo used as a control to ensure reliability
  • Dosage of the drug is tested and increased to optimum levels
• In double blind trials:

  • One of the drugs is a placebo, which has no effect
  • The doctor and patient do not know which drug is the placebo to avoid bias
  • Doctor's unawareness prevents unintentional clues that could affect the test results
• Peer review process:

  • The entire drug development process is peer-reviewed by another doctor before the drug can be released
• In a graph showing antibody production after vaccination and after contraction you will see that after contraction antibodies are produced sooner and more quickly and more of them are produced and production lasts for longer. 
• Vaccinations are one way of preventing the spread of disease. A weakened/dead strain of a pathogen is injected into the body. This triggers the immune system and the B-lymphocytes produce antibodies that are specific to the antigens on the chosen pathogen. The vaccination itself rarely hurts the patient but memory cells are created which store the information on how to produce the specific antibodies so if the person contracts the disease they will be able to quickly produce antibodies
• If the majority of a population is vaccinated against a disease it is called herd immunity. This is beneficial because if a large enough amount is vaccinated, even the unvaccinated people have a much lower chance of contraction so spread is reduced.
• Plants can have potassium, phosphorous, nitrates or magnesium defficiency
• Potassium minerals are used for fruits and flowers. Without them, leaves turn yellow. Phosphorous minerals are used for roots. Without them, leaves turn purple.
• Antibodies specific to a hormone (HCG) found in a pregnant woman’s urine are used in pregnancy tests
• Mobile antibodies containing blue dye are in the reaction zone
• As urine moves up, hormones bind to the antibodies and are carried to the result window with immobilised antibodies
• Hormones also bind to immobilised antibodies in the result window, producing a line of blue dye
• Control window contains immobilised antibodies specific to the reaction zone antibodies to check if the test is working