• Created by: Davina1st
  • Created on: 18-05-21 19:25
What are the four types of pathogens?
Bacteria, viruses, fungi and protoctista
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What is a communicable disease?
A disease cause by an infectious organism (pathogen).
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What is a vector?
Something that carries a pathogen from one organism to another, which spreads the disease.
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Bacteria are eukaryotes, true or false?
False - bacteria are prokaryotes.
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What are the two ways in which bacterium can be classified?
Their basic shapes and by their cell walls.
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Give an example of some shapes of bacteria pathogens
Rod shaped, spherical, comma shaped, spiralled and corkscrew.
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How are different bacteria identified by their cell wall?
By gram staining
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How does gram staining work?
Gram positive look purple-blue under a light microscope (MRSA) and gram negative bacteria appear red (E.coli).
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Describe a virus pathogen
Non-living, 0.02-0.03 um in diameter=50x smaller than bacteria. Genetic material surrounded by protein. Virus invades the living cell and takes over host=rapid reproduction.
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What is a virus that attacks bacteria called?
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Describe protoctista
Eukaryotic, including single-celled and cells grouped into colonies. Protists which cause a disease are parasitic - use animals/plants as their host.
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Describe the structure of a fungus and how it gains its food
Eukaryotic and multi-cellular, they cannot photosynthesise, so they contain digestive enzymes to digest food extracellularly before absorbing the nutrients.
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How does fungi reproduce?
By releasing spores (sometimes 1 million at a time) so they spread quickly.
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What are the 2 modes of action by pathogens?
damaging the host tissue directly or producing toxins to damage host tissues.
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What is a viruses mode of action? Describe it
Damage host tissues directly - Viruses take over cell metabolism, viral genetic material gets into host cell and is inserted into host DNA, the host cell is used to make more virus cells=spread and more infection.
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How do pathogens produce toxins which damage the host tissue?
Bacteria produce toxins that poison the host cell in some way, causing disease. Some break cell membranes, damage/inactivate enzymes and some interfere with genetic info. Toxins are a by-product of normal bacteria functioning.
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What are the three types of direct transmission of diseases?
Direct contact (kissing, skin to skin, faeces to hands), inoculation (through break in the skin, animal bit, puncture wound), ingestion (taking in contaminated food/drink)
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What are the three types of indirect transmission?
Fomites (inanimate objects like bedding, socks and cosmetics), Droplet infection (saliva and mucus from one individual to another), vectors (transmits communicable diseases from one host to another)
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What are some factors that affect the transmission of communicable diseases in animals?
Probability of catching increases by overcrowded/poor living conditions, poor nutrition, compromised immune system, poor disposal of waste, climate change (introduce new vectors and pathogens), socio-economic factors.
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How does soil contamination lead to indirect transmission of a plant disease?
Infected plants leave pathogens/reproductive spores from protoctista or fungi in the soil. These can infect the next crop, some pathogens can survive the composting process so the infection cycle can be completed with contaminated compost.
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How can vectors lead to the indirect transmission of plant diseases?
By wind (spores are carried in the widn to other crops), water (spores swim on the surface film of water/raindrop splashes), animals (isnects and birds can carry pathogens from one plant to another), humans (pathogens/spores transmitted by fomites).
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What are some factors affecting the transmission of communicable diseases in plants?
Planting a variety of crops susceptible to disease, over-crowding increases the likelihood of contact, poor mineral nutrition reduces resistance of plants, damp/warm conditions increase survival of spores and pathogens, climate change-increased rain
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How can the spread of communicable diseases in plants be reduced?
Leave plenty of room between plants to minimise the spread of pathogens, clear fields as thoroughly as possible, rotate crops, follow strict hygiene, control insect vectors.
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Describe the process of how a plant recognises the attack of a pathogen
Receptors in the cell membrane respond to molecules from the pathogen, or to chemicals produced when the plant cell wall is attacked. This stimulates the release of signalling molecules that switch on genes in the nucleus=trigger cellular repsonses.
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Describe the physical defences of a plant (callose)
Callose is synthesised and deposited between the cell walls and cell membranes, next to infected cells. Acts as barriers, preventing pathogens entering the surrounding plant cells. Lignin added=thicker. Callose blocks sieve plates in phloem.
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What are some chemical defences of a plant?
Insect repellents (citronella), insecticides (caffeine and other chemicals), antibacterial compounds (phenols/defensins/lysosomes), antifungal compounds (chitinases), anti-oomycetes (glucanases), general toxins.
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What are some non-specific responses to disease? (animals)
The skin acts as a barrier, mucous membranes trap pathogens and cilia beat to remove it, lysosomes in tears and urine, blood clotting, fever stops pathogens reproducing, histamines and cytokines.
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How does blood clotting/wound repair work?
Platelets are activated by damaged tissue and release thromboplastin which cascades the reaction of fibrin to forma blood clot.
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What is a phagocyte?
Specialised white blood cells that engulf and destroy pathogens. 2 main types, neutrophils and macrophages.
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Describe the process of phagocytosis
Pathogens produce chemicals which attract phagocytes, they recognise the non-self proteins on the pathogens and engulf it into a vacuole (phagosome). Phagosome combines with lysosome=phagolysosome. Enzymes from lysosome digest + destroy the pathogen.
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What is an antigen?
Any substance that when introduced to the blood/tissue, induces the production of antibodies.
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What is an antibody?
Protein produced by B cells/plasma cells in the presence of foreign cells.
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Describe the structure of an antibody
Y shaped glycoprotein=immunoglobins, two identical long polypeptide chains =heavy and light. Chains held together by disulphide bridges. Variable regions= specific shape to fit antigen depending on amino acid sequence.Hinge regions attach light+heavy
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What are the four ways in which antibodies defend the body?
Neutralisation, antigen-antibody complex, agglutination and opsonisation.
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How does neutralisation work? Antibodies
Antibodies act as anti-toxins, binding to toxins produced by pathogens and making them harmless.
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How does agglutination work? Antibodies
Antibodies act as agglutins, causing pathogens carrying antigen-antibody complex to clump together which stops them from spreading so they are easier to engulf.
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What is opsonisation? Antibodies
Antibody of complex cells acts as an opsonin so the complex is easily engulfed and digested by phagocytes. Receptor on phagocyte binds to constant region on phagocyte.
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What is the function of the variable regions?
They have different shapes due to the different sequences of amino acids, which means the antibody is specific to the shape of the antigen. Attaches to the antigen
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What is the function of the hinge regions?
Allows for movement without the antibody breaking
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What is the function of the constant regions?
Same in all antibodies- receptor on phagocyte binds to the constant region so the pathogen cant escape.
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What is the function of a T-Helper cell?
They have receptors on their CSM which bind to surface antigens on APC's. They produce interleukins (type of cytokine). Interleukin stimulates the activity of B cells=antibody production.
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What is the function of a T-Killer cell?
Destroy the pathogen carrying the antigen, produce perforin (makes holes in pathogens cell membrane which makes them very permeable)
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What is the function of T-Memory cells?
Live for a very long time, during secondary response they divide rapidly to form clones of T-killer cells that can destroy the pathogen.
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What is the function of T-regulator cells?
Supress the immune system, to control and regulate it, makes sure the body recognises self-antigens.
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What is the function of a B-effector cell?
They divide to form plasma cell clones
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What is the function of B memory cells?
Provide immunological memory, during secondary response, they remember the specific antibody to fir the antigen and start a rapid response.
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What is humoral immunity?
Produces anibodies that are soluble in the blood and tissue fluid and are not attached to cells.
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Describe the process of humoral immunity
T cell binds to B cell APC (clonal selection of correct B cell antibody) interleukins produced by T cell activates B cell. B divides by mitosis=plasma and memory cells (clonal expansion) Cloned plasma cells make correct antibody.
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What is cell mediated immunity?
Where T-Lymphocytes repsond to the cells of an organism that have been changed in some way e.g. virus infection/early cancers.
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Describe the process of cell mediated immunity
Receptor on T-helper cell fits the antigen, T helper becomes activated=interleukins=clonal expansion -dividing by mitosis. Clones of identical T helper with correct antibody are formed. Cloned T cells can =memory cells, produce interleukins, plasma.
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What is an autoimmune disease?
When the immune system recognises self cells and starts to attack healthy body tissue.
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What are the possible causes of an autoimmune disease?
Genetic tendency - sometimes immune system responds abnormally to a mild pathogen/ T-regulator cells don't work properly.
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Why use immunosuppressants to treat autoimmune disease?
They prevent the immune system from working and therefor stop the attacking of healthy body tissue.
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What is a risk of immunosuppressants?
The body is deprived of its natural defences against communicable diseases.
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Give three types of autoimmune disease
Type 1 diabetes, rheumatoid arthritis, lupus
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Why do we vaccinate against certain diseases?
To protect the individual from catching a life threatening disease and to stop the spread between people.
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What do vaccines contain?
Killed/inactivated pathogens, attenuated (weakened strands) of live bacteria/viruses, toxin molecules that have been detoxified, isolated antigens extracted from the pathogen. genetically engineered safe antigens.
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How are vaccines administered?
Small amounts of the safe antigen are injected into the blood stream. Inhaled up nose and liquid drops.
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How does your immune system respond to the vaccine?
Primary: triggered by the foreign antigens, body produces antibodies (clonal selection and reproduction) and memory cells. Secondary: pathogen destroyed rapidly before you show any symptoms.
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What is natural active immunity?
Immunity gained by your own body acting to produce antibodies.
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What is natural passive immunity?
Immune system of a baby is weak, antibodies from the mother are passed to the child through the placenta, or breast feeding (colostrum)
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What is artificial passive immunity?
The immune system is stimulated to make antibodies from a safe form of the antigen (vaccine)
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What is artificial passive immunity?
Antibodies formed in one individual are extracted and injected into another.
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What does the term herd immunity mean?
95% of the population are vaccinated and immune to a virus as they have the antibodies against a disease. The vast majority.
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How does vaccination protect a population from a specific disease?
Memory cells from first introduction of pathogen mean milder symptoms. Some individuals who do have the disease are unable to spread it.
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Why are there no vaccines for malaria yet?
Plasmodium (the protoctista that causes malaria) is very evasive, it is found in erythrocytes so is protected by self antigens from the immune system and within the infected person the antigens reshuffle, they have a complex life cycle.
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Why is there no vaccine for HIV yet?
Causes AIDS which enter macrophages and T-helper cells so has disable the immune system altogether.
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What is the source of penicillin?
Commercial extraction, originally from mould on melons.
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What is the source of docetaxel?
Derived originally from yew tree
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What is the source of aspirin?
Based on compounds from swallow (willow) bark.
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What is the source of prialt?
From venom of cone snails in oceans around Australia.
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What is synthetic biology?
Using genetic engineering to produce bacteria that will form drugs which would otheriwse be too expensive/rare. Enables the use of bacteria as biological factories.
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What is the difference between a broad and narrow spectrum antibiotic?
Narrow spectrum is an antibiotic that targets a few types of bacteria, whereas a broad antibiotic targets many types of bacteria
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How does antibiotic resistance develop?
Random mutation in one bacterium produced a gene for antibiotic resistance, this leads to a population with few antibiotic resistance - continued selection means the population of antibiotic resistance increases.
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What are the long term measurements being taken to combat antibiotic resistance?
Minimising the use of antibiotics - ensuring every course of antibiotics is completed. Good hygiene in hospitals - stops spread of antibiotic strains.
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What are some sources of potential new antibiotics?
Soil microorganisms, crocodile blood, fish slime, honey and abysses' of oceans.
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How does a female mosquito transmit malaria?
Female mosquitoes drink blood to gain protein from the haemoglobin, saliva injected to stop blood from clotting, the parasites in the salivary glands liver cells and enter red blood cells.
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Bacteria are eukaryotes, true or false?


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Card 5


What are the two ways in which bacterium can be classified?


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