INFECTION AND RESPONSE

Communicable diseases

  • Microorganisms - bacteria, viruses, protists and fungi, and some can cause issues in the body

  • Pathogens are microorganisms that cause disease

  • Pathogens spread by:   

    • Air - influenza and measles, tiny droplets that we cough or sneeze

    • Contaminated food - salmonella

    • Contaminated water - Cholera and bacteria diseases

    • Direct contact - athlete’s foot (fungal), through contaminated surfaces

  • We can stop the spread of pathogens by:

    • Hygiene - washing hands, clean cooking items

    • Killing the vectors🗡 - mosquitoes carrying malaria can be killed by insecticides

    • Isolation - for serious diseases

    • Vaccination - Can’t catch, so therefore can’t pass on

Viral diseases

  • Viruses aren’t cells and are not living and can’t reproduce, they are considered organisms

    • They go inside other cells and use them to reproduce - can burst cell and move to other cells which is damaging and dangerous

  • Measles

    • Spread by droplets in the air - from sneezes and coughs

    • Causes a red rash and a fever

    • Can be fatal

    • Most people are vaccinated

  • HIV

    • Spread through sexual contact and exchanging of bodily fluids (needles)

    • Causes an inadequate immune system

    • Can cause flu like symptoms (fevers, tiredness and aches), and then start to fell better though still infected

    • Virus damages immune system and catches unusual infections - can develop into cancers

    • Person can develop AIDS - a system/syndrome when an immune system can’t cope

    • Treated by antiretroviral drugs, which prevent the virus replicating

  • Tobacco mosaic virus

    • Affects plants (tomato and tobacco)

    • Causes a mosaic pattern on leaves, so photosynthesis is slowed can’t occur - a lack of sugars for growth                    

Bacterial diseases

  • Bacteria is mainly good, but there are a few bad ones that cause diseases :(

  • Bacteria are single celled organisms

  • They can reproduce by themselves

    • They are often in our bodies as good food supply, and they can produce toxins - cause illness

  • Salmonella

    • Causes food poisoning

    • Mainly from chicken (who had disease when alive)

      • In the UK, most are vaccinated against it

    • Causes fever, stomach cramps, vomiting and diarrhoea ( as it affects the intestines)

    • Passes in about a week and hydration is important

  • Gonorrhoea

    • Sexually transmitted disease

    • Causes pain when urinating and thick discharge

    • Prevented by barrier contraception

    • Treated by penicillin - however many stains are resistant to it

      • Instead, rarer and more expensive antibiotics are used

Fungal diseases

  • Fungi are eukaryotic cells, and can be unicellular (yeast) or multicellular

  • Multicellular can be mushrooms, often have long thread-like structures (hyphae), can penetrate skins and produce spores

  • Rose black spot

    • Causes purple/black spots on leaves

    • Can cause leaves to turn yellow and drop off, which causes reduced photosynthesis, leading to less growth

    • It spreads in the water and air

    • Treated by cutting of infected leaves and destroying them, or spraying with fungicide

  • Athlete’s foot

    • Causes a rash - dry red and flaky or white, wet and cracked skin

    • Transmitted by touching infected skin or contaminated surfaces

    • Treated by antifungal medication

Protist diseases

  • Protists are eukaryotic cells that can be multicellular or unicellular (majority)

  • Some are parasites and live in/on another organism

  • They are often transmitted by vectors (malaria and mosquitos)

  • Malaria

    • Caused by a parasitic protist and needs a host to survive

    • Transported by mosquitos, who feed on an animal with malaria , the mosquito ‘sucks up’ the parasite, and then feeds on another animal and spreads it to a new most

    • Causes fever, headaches in recurrent episodes and can be fatal in humans

    • Prevented by destroying mosquito breeding sites, killing with insecticides and stopped with mosquito nets and repellent

Human defence systems

  • Physical and chemical barriers

    • Skin - a physical barrier that secretes oil and antimicrobial structures that kill pathogens

    • Nose/mouth - The nose has lots of hairs and mucus to trap pathogens

      • The trachea/oesophagus has a mucus layer and cilia to waft pathogen back up to nose

      • Stomach kills pathogens with acid

  • Immune systems

    • White blood cells

      • Phagocytosis - Wbc can engulf some pathogens, so we can track the pathogens to later bind and engulf

      • Anti-toxins - Wbc produce and they can bind and counteract pathogens and toxins

      • Antibodies - Small proteins that act as a signal and bind onto pathogens so Wbc’s can come and destroy them

        • They are specific to certain antigens

Vaccinations

  • Once our bodies and immune systems have been exposed to a pathogen, they become immune to it and it’s diseases

    • This is why we can only catch some diseases once, like measles

  • To protect ourselves from pathogens, we need to be exposed to the disease without actually catching it, as it could be lethal if caught

  • Vaccines are a weakened or dead version of a pathogen that still contains the antigens needed to produce antibodies that lead to immunity

  • They can work bacterial and viral diseases

  • PROS - Protection against pathogens

    • Control over common diseases

    • It can prevent outbreaks and epidemics, which kill a lot of people

    • Herd immunity - when enough people in a community are vaccinated, the pathogen won’t have anyone to spread to, so when the host overcomes the disease or dies, the pathogen disappears

  • CONS - Vaccines don’t always work and don’t necessarily grant full immunity

    • Can cause bad reactions, like swelling or seizures, although rare

Antibiotics and painkillers

  • Antibiotics treat the disease by preventing growth or killing the bacteria

    • They can only treat bacterial diseases

    • They are specific to each type of bacteria and each target a different type of bacteria

  • Antibiotic resistance is when strains of bacteria adapt to become resistant to the antibiotic and no longer work

  • Painkillers only relieve symptoms and don’t help cure the problem

Discovery and development of drugs

  • New drugs are constantly being developed, often from plants and microorganisms

  • The first antibiotic made was penicillin and discovered by Alexander Fleming

    • He went on holiday, and when he came back there was mould growing in his petri dish that killed of bacteria that was already growing

      • Penicillium mould became penicillin antibiotic

  • Aspirin - made from willow bark and it lowers fevers

  • Digitalis - a heart drug that is extracted from foxgloves

  • Drugs can be made from plants and microorganisms - can be directly used or modified in a lab

  • Testing

    • We test for efficacy, toxicity and dosage

  • Stage 1 testing - pre-clinical

    • Testing on human cells and tissues 

    • Cheaply test lots of possible substances

    • Doesn’t show effect on whole organisms or organs

  • Stage 2 - pre-clinical

    • Testing on live animals

    • In UK, you have to test on at least 2 mammals

    • Shows effects and ideas around efficacy and toxicity

  • Stage 3 - clinical

    • Testing on healthy volunteers with a low dosage, which is slowly increased to find the maximum without side effects

    • Testing on patients with the illness

      • A low dosage which is very slowly increased to find the optimum dosage (max efficacy, min toxicity)

  • Blind testing is when both placebo and real drugs are used and the volunteers don’t know which they are getting

  • Double-blind testing uses placebo and real drugs and the doctors also don’t know which is which

    • Both are used to avoid biases

      • The volunteers knowing they took the drug might report more side effects

      • Doctors might notice or expect more side effects, so question more

  • Peer reviews are where results are analysed by other scientists, to prevent false results or claims

Producing monoclonal antibodies

  • Monoclonal antibodies are a single clone of a specific cell made to produce antibodies

  • Antibodies are small proteins produced by white blood cells (lymphocytes)to help fight disease

    • They bind onto foreign material - antigens

    • They are specific to certain bacteria

  • They are made in a laboratory

    • This requires lots of B-lymphocyte clones (they don’t duplicate very quickly, so need something to increase rate)

    • We can combine B-lymphocyte clones with fast-dividing tumour cells - forms a hybridoma

  • Hybridomas - produce lots of antibodies

    • Divide rapidly, in a petri dish, and are them collected and purified

  • We collect these white blood cells and inject an animal with them with the antigen we want our antibody to bind to 

    • This produces the lymphocytes that we can isolate and fuse

  • They always bind to one specific thing ,and with the right B-lymphocyte we can create antibodies that bind to anything we want

    • For example, protein or cells in the body, a pathogen or chemical 

  • We can attach things to the antibody, likes to drugs, fluorescent proteins or radioactive materials, to deliver it to certain areas

Uses of monoclonal antibodies

  • Pregnancy tests 

    • Pregnant women produce a hormone called HCG, which is excreted in urine

    • They are cheap, reliable and quick

    • In the test strip, there are blue beads covered in antibodies (specific to HCG) that are free to move at one end

    • In the middle, there are the same antibodies fixed to the test strip

    • If the women is not pregnant, the urine washes the blue beads down the strips and over the fixed antibodies, so it doesn’t go blue

    • If the women is pregnant, the urine will contain HCG, which binds to the blue beads and antibodies on them

      • When the urine washes over the fixed antibodies, it binds to them as well and the beads stay, so the strip appears blue

  • Cancer diagnosis and treatment

    • If a person with cancer is injected with monoclonal antibodies, they will bind to the tumour and cancerous cells and will ‘clump’ together

      • This makes it easier to identify tumours

      • We can carry drugs (attached to the antibodies) directly to the tumour

      • We can encourage the immune system to directly attack cancerous cells

Detection and identification of plant diseases

  • Plants can catch diseases from fungi, bacteria, viruses, insects and have deficiency diseases (stunted growth)

  • Symptoms of plant diseases could be abnormal growth or lumps, patches of decay, discolouration on leaves, malformed stem or leaves and aphids or spider mites

  • We can diagnose plant diseases by

    • Basic observation - match a gardening manual or website with findings

    • Take a tissue sample and send to a plant pathologist, who look at unique antigens and take DNA tests

    • Trial and error to treat

Plant defence systems

  • Physical defences 

    • Waxy cuticle

    • Cellulose (cell walls)

    • Dead cell layers (bark)

  • Chemical defences

    • Antimicrobial

    • Poisons

  • Mechanical defences

    • Thorns

    • Hairs

    • Leaves dropping off or curling if insects land on them to prevent infection

DONE!!