INFECTION AND RESPONSE

• Pathogens

  Microorganisms that can cause infectious diseases e.g bacteria, fungi, protist, viruses
• How pathogens spread

  1. Air- tiny droplets that expel when cough or sneeze
  2. 2. Contaminated food and water
  3. 3. Direct contact- sexual contact
• how to stop spreading pathogens

  1. Hygiene- washing hands, cleaning cookery items
  2. Kill vectors- such as mosquitos using insecticides
  3. Vaccination
  4. Isolate/quarantine
• viruses

  Cannot reproduce by themselves but once they infiltrate an organism they use the organism mechanism to make copy of themselves and then burst, spreading new viruses
• measles

  • spread by droplets (cough or sneeze), develop rash/ fever, vaccination
• HIV

  spread by sexual contact or exchanging bodily fluids. 'Human immunodeficiency virus.' Flu-like symptoms such as fever, tiredness, aches. Can develop into aids but can be controlled by antiretroviral drugs which prevent virus from replicating
• tobacco mosaic virus

  • gives distinctive mosaic discolouration, photosynthesis is unable to take place so can't produce sugars for proper growth
• salmonella (bacterial)

  • food poisoning, fever, stomach cramps, vomiting, diarrhoea. Infects intestine
• Gonorrhoea (bacterial)

  • STD, pain when urinating, yellow or green thick discharge. Use protections and contraception. penicillin , however a lot of gonorrhoea strains have become resistant
• Rose black spot (fungi)

  • purple or black spots develop on leaves. Reduces photosynthesis, prohibits growth and leaves fall off. Spread by water or wind. Treated using fungicides or cutting off infected leaves and destroying them
• Malaria (protists)

  • transported by vectors (mosquitoes) live on inside another organism, spread to different hosts. Fever and headaches (recurrent episodes). Destroy mosquito breeding sites, use mosquito nets or insecticides. antimalarial drugs
• Physical and chemical barriers

  • Skin- physical barrier, secrets oils/ antimicrobial substances kill pathogens
  • Nose- mucus to trap pathogens
  • Trachea/oesophagus- Layer of mucus to trap particles, lined with cilia that move mucus to the back of the throat to be swallowed into stomach
  • Stomach produces HCL which kills all pathogens
  • eyes- produces tears containing enzymes that kill bacteria
• Immune system (wbc)

  • Phagocytosis -  track bind and engulf pathogens
  • Antitoxins - small  molecules that bind and counteract toxins
  • Antibodies - antigens are foreign substances that are then locked onto by specific antibodies (small proteins) to act as a signal. Remembers it for next time for quick immune response
• VACCINATION

  • Injection of dead/inactive pathogens into the body to stimulate white blood cells to produce antibodies
• Pros of vaccination

  • Protection from diseases
  • Control of common diseases
  • Prevent outbreaks (epidemics)
  • Herd immunity- when large population are immune the pathogen can't spread, so once host overcomes disease or dies the pathogen disappears
• Cons of vaccination

  • Don't always work
  • Bad reactions (swelling,seizures, fevers)
• Antibiotics

  • Sticks to the antigen on a pathogen, neutralizing it and making it clump together so phagocytes can ingest and destroy it.
  • can't kill viruses
• Painkillers

  Relieve the symptoms e.g aspirin, paracetamol, cough medicine. Don't cure the problem
• drug development

  • Aspirin- willow trees, pain killer, lowers fevers
  • Digitalis-  foxgloves, treat heart problems
  • Penicillin- Alexander flemming from penicillin mould
• things to keep in minds when testing drugs

  • Efficacy- how well the drug works
  • Toxicity- how harmful the drug is (side effects)
  • Dosage- how much of the drug (concentration)
• Drug testing

  1. Drug tested on human cells and tissues, cheap test. Doesn't tell us how it'll affect organ/organism
  2. Testing on live animals (preclinical), test efficacy and toxicity
  3. Clinical testing ( give to healthy volunteers), low dosage and increase dose until max dosage without side effects
  4. Test on those suffering from illness and slowly increase dosage until you find optimum dosage where efficacy is maximise and toxicity is minimised
  5. Placebo- like the real drug but won't do anything to ensure results are valid. Peer reviewed by other scientist to prevent false claims
• Double-blind test

  Don't tell volunteers or doctors which drugs are being taken (double blind test).
• monoclonal antibodies

  • Produced from single clone of cells
  • Antibodies are specific to one binding site on one protein antigen
  • B-lymphocyte clones combine with fast dividing tumour cells to form hybridoma, producing lots of antibodies which also divide rapidly. In petri dish there will be a lot of hybridoma which is identical then collected and purified
  • B-lymphocytes come from an injected animal with the antigen we want our antibody to bind to
  • Bind to one specific thing, can attach things to the bottom such as drugs, fluorescent proteins or radioactive material
• uses of monoclonal antibodies

  • Diagnosis in pregnancy test
  • Measure levels of hormones, chemicals in blood or to detect pathogens
  • In research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye
  • To treat some diseases: for cancer the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing. It delivers the substance to the cancer cells without harming other cells in the body
• plant disease symptoms

  • Stunted growth
  • Spots on leaves
  • Areas of decay
  • Discolouration
  • Malformed stems or leaves
  • Presents of pest
• diagnose plant diseases

  1. Gardening manual or website
  2. Infected plants to laboratory
  3. testing kits using monoclonal antibodies
• Nitrate deficiency

  • Can stunt plant growth as nitrates in the soil convert sugars made in photosynthesis into proteins needed for growth
• magnesium deficiency

  • Can cause chlorosis (parts of the leaves appear green and yellow) as magnesium is needed to make chlorophyll, the green pigment vital for photosynthesis
• physical defence of plants

  • Tough waxy cuticle stops entry into leaves
  • Cellulose cell walls form a physical barrier into the cells
  • Layers of dead cells around stems (such as bark) which stop pathogens entering
• chemical defence of plants

  • Poisons (e.g from foxgloves, tobacco plants, deadly nightshades, yew) deter herbivores
  • Antibacterial compounds kill bacteria, such as mint plant and witch hazel
• mechanical defence of plants

  • Thorns and hairs make it difficult and painful for animals to eat them
  • Leaves can droop or curl when touched which allows them to move away and move insects off their leaves
  • Mimicry to trick animals (e.g. droop to look unhealthy, patterns to look like butterfly eggs, stone/pebble like appearance)
• preventing development of resistant bacterial strains

  1. Stop overusing antibiotics - this unnecessarily exposes bacteria to the antibiotics
  2. Finishing courses of antibiotics to kill all of the bacteria
• producing monoclonal antibodies

  1. Scientists obtain mice lymphocytes (a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific antibody
  2. They are combined with tumour cells (do not make antibodies but divide rapidly), to form a cell called a hybridoma
  3. The hybridoma can divide to produce clones of itself, which all produce the same antibody
  4. The antibodies are collected and purified
• advantages of monoclonal antibodies

  • They only bind to specific cells, meaning healthy cells are not affected
  • They can be engineered to treat many different conditions
• disadvantages of monoclonal antibodies

  • It is difficult to attach monoclonal antibodies to drugs
  • They are expensive to develop
  • As they were produced from mice lymphocytes, they often triggered an immune response when used in humans