• Created by: Chloe
  • Created on: 28-02-17 20:12
What are bacteria?
They are a type of pathogen. They are prokaryotic cells. There are two classifying methods: shape and cell wall.
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What are viruses?
They are very small, between 0.02 - 0.3 micrometers. They are non-living and consist of DNA surrounded by a protein coat. They reproduce by taking over living cells.
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What are fungi?
They mainly cause disease in plants. They are multicellular eukaryotic cells.
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What are protoctists?
They are single celled eukaryotic cells. They require a vector to be transferred. They can also be transferred by water.
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What is a communicable disease?
It is an infectious disease transmissible by direct and indirect contact.
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What is direct transmission?
Direct contact, inoculation and inhalation.
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What is indirect transmission?
Vector, droplet inhalation and fomites.
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What is callus?
They have 1,3 glycosidic bonds. Its a polysaccharide. Its important in plant response to infection.
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What is thromboplastin?
It is an enzyme which starts many reactions.
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What is serotonin?
It makes smooth muscle contract. This restricts the blood flow in the blood vessels.
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What are mast cells?
They are a type of white blood cell. They are rich in histamines.
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What are histamines?
It causes dilation of blood vessels resulting in redness and heat which inhibits pathogen reproduction. It makes blood vessel walls leaky, forcing blood plasma out (this is now called tissue fluid), this causes swelling.
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What are cytokines?
They attract phagocytes. They are cell signalling molecules. And they increase body temperature.
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How do viruses work?
They take over a cells metabolism. The virus DNA enters the host cell. Viruses use host cells to make new viruses. This is how they replicate.
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How do protoctists work?
They take over cells but not genetic material. They digest the cell and use its contents.
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How do fungi work?
They digest and destroy living cells. They cause symptoms of disease. They also produce toxins.
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How do bacteria work?
They produce toxins which cause symptoms of disease. These poison or damage host cells.
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What are the three types of direct transmission?
Direct contact, inoculation and ingestion.
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What are the three types of indirect transmission?
Fomites, droplet inhalation and vectors.
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What increases the probability of catching a communicable disease?
A compromised immune system, poor nutrition, poor waste disposal, climate change, overcrowding and socio-economic factors.
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What increases the probability of plants catching a communicable disease?
Overcrowding, poor mineral nutrition, climate change, damp, warm, plenty of oxygen.
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What defences do plants have against disease?
Waxy cuticle, lignin, bark, callus and cellulose.
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Whats the difference between cellulose and callose?
Cellulose has 1,4 glycosidic bonds whereas callose has 1,3.
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Role of callus
1. Synthesised. 2. Deposited in neighbouring cells near to infected cells between cell wall and membrane. 3. Still added after initial infection. 4. Lignin is added for strength. 5. It blocks of sieve plate. Cutting off infected part.
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Plant responses
Quick as they are not passive. They detect chemicals and molecules produced by pathogens. Pathogenic enzymes break down cell wall. Signalling molecules alert nucleus. Polysaccharides (callose, lignin) strengthen cell wall. Defence chemicals produced.
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Plant chemical defences
Anti-bacterials - PHENOLS. Insecticide - CAFFEINE. Insect repellent - PINE RESIN. Anti-fungal - GOSSYPOL. Anti-oomycetes - GLUCANASES.
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Primary non-specific animal defences
Skin - Sebum lowers pH making bacteria growth harder. Sweat is salty creating an environment which bacteria struggle to grow in. Tears - Again create a salty environment. Eyelashes - Prevent dirt/bacteria entering eyes. Mucus - Traps bacteria.
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Other primary non-specific defences
Digestive system - Stomach pH is very low, making it hard for microorganisms to survive. Expulsive reflexes - Remove microorganisms from the body.
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What is immunisation?
The action of making a person or animal immune to an infection, typically by inoculation.
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What are the stages of an inflammatory response?
1. Mast cells are activated. 2. Histamines and cytokines released. 3. Histamines cause dilation of the blood vessels which results in swelling. 4. Histamines make blood vessel walls leaky. 5. Cytokines attract phagocytes.
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What is a vaccine?
Injection of a pathogen (weakened or killed) which produces immunity in the body against that pathogen.
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Blood Clotting Stages
1. Cut. 2. Pathogens enter. 3. Clot seals wound. 4. Platelets and skin come into contact. 5. Platelets secrete thromboplastin, serotonin. 6. Clot dries. 7. Epidermal cells grow under scab permanently seal wound. 8. Collagen deposited. 9. Scab falls.
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Stages of Phagocytosis
1. Cytokines attract phagocyte. 2. Phagocyte binds to pathogen. 3. Pathogen engulfed. Phagosome formed. Lysosome combines with phagosome forming a phagolysosome. 4. Pathogen broken down by enzyme. 5. Digested pathogen absorbed by phagocyte.
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Phagocytosis continued
6. Antigens combine with MHC. 7. MHC displayed on phagocyte membrane making an APC.
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What is cell-mediated immunity?
T lymphocytes recognise an altering of cells. Macrophages engulf and digest pathogens. Antigens get processed forming APCs. Some T helper cells have receptors with a complementary shape to the antigen. Activating t helper cells produces interleukins.
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Interleukins stimulate T cell division by mitosis. Cells produced are clones of T helper cells.
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What is humoral immunity?
It is the response to antigens outside of the cell. Antibodies are produced. B lymphocytes have antibodies on their membrane. Many b lymphocytes, many antibodies. B lymphocytes process antigens becoming APCs. Activate T helper activates B cell.
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Activated B cell undergoes mitosis. Plasma and B memory cells produced. Process is called clonal expansion. Plasma cells produce antibodies. Bind and disable pathogens.
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What do cloned T cells do?
Produce interleukins which stimulate phagocytosis. Develop T memory cells. Produce interleukins which stimulate B cell division. Produce T killer cells which destroy pathogens.
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Primary Response
This is the slowest of the two responses. It takes days - weeks to become fully effective meaning we feel ill. It is where the pathogen first enters the body. It activates B and T lymphocytes. Symptoms are felt.
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Secondary Response
After first response, some memory cells stay in the blood. They remember what antibodies were required and quickly secrete them when the pathogen enters again. Its a fast response, requires activated memory cells and no symptoms are felt.
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T helper cells
Have CD4 receptors. CD4 binds to antigens on APCs. Interleukins are produced which stimulate B cell activity.
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T killer cells
Destroy pathogen. Produce perforin. It kills the pathogen by making a hole in its membrane.
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T memory cell
Live for a long time. They divide rapidly into T killer cells in response to a pathogen entering the body on its second time of invasion.
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T regulator cells
Regulate and suppress the immune system. Stops the immune response after eliminating pathogen. It prevents autoimmune diseases by making sure body recognises self-antigens.
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Plasma cells (B)
Produce specific antibodies. Only live for a few days. Produce 2000 antibodies per second.
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B effector
Divides to form plasma clones.
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B memory cell
Live for a long time. Produce a rapid response. Remember specific antigens.
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They are y-shaped glycoproteins called immunoglobulins. Specific antibodies for each antigen.
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Antigen binding site.
Enables antibody to and to a specific antigen.
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Disulphide bridges
Hold 4 polypeptide chains together. They are strong covalent bonds between cysteine amino acids.
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Polypeptide chains
Each antibody consists of 4 polypeptide chains - 2 identical lights and 2 identical heavy.
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Artificial immunity
2 types, active and passive. Active: Antigens enter body by a vaccine causing antibody production. Passive - Antibodies injected into body.
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Natural immunity
2 types: active and passive. Active: Pathogens naturally enter body and as a result, antibodies are produced. Passive: Antibodies pass from mother to foetus by placenta or mothers breast milk.
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Autoimmune diseases
Occur when the body's immune system doesn't recognise self-antigens. Could be due to a lack of T regulator cells. This results in the body attacking self-cells. Includes diseases such as diabetes and lupus. Treatment includes immunosuppressants.
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It is a communicable disease which regularly changes. This is called antigenic variation. Arises due to antigens changing by mutations. Means it is hard to vaccinate. 2 types: antigenic shift and antigenic drift.
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Antigenic drift
Involves mutation causing minor change.
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Antigenic shift
Major change due to genetic recombination.
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Example of artificial active immunity. Can also be an example of passive when treating fatal disease which require antibody vaccines as immune system is too slow. Vaccines are made safe by using killed, inactive or weak strains of pathogen.
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What do vaccines do?
A small dose triggers a primary response. This means that when you encounter the actual pathogen, the secondary response is triggered. This type of immunity can last for varying lengths of time or a life time. Boosters are often required.
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Live, weakened vaccines
Strong immune response, life long immunity. Not safe for people with compromised immune systems and needs refrigeration.
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Inactivated, killed vaccines
Safe for people with compromised immune systems. No refrigeration needed. Needs booster shots.
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Subunit vaccines
Lower chance of an adverse reaction. Research can be time consuming.
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Conjugate vaccine
Safe for people with compromised immune systems. Usually requires booster shots.
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Source: Rainforest and potentially other microorganisms. Common medicines: caffeine, cocaine, heroin and capsaicin.
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It inhibits the growth of bacterial cells.
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Prescribed drugs. Used on bacteria. Shouldn't be used on viruses. Two types: bacteriostatic and bactericidal.
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Directly destroys the bacterial cells.
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Antibiotic resistance
Some bacteria are resistant to antibiotics. E.g. MRSA and Clostridium difficile. Arises due to mutation in bacterium DNA. Mutation means bacterial cell wall could synthesis a new protein. Mutations are random and rare. Conjugation is a problem.
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Bacterial cell wall synthesis
They have an influx of water by osmosis. Entry of water without a rigid cell wall causes osmotic lysis. Rigid cell wall of bacteria means they can withstand expansion and prevent further water attention. Prevents osmotic lysis.
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Inhibit the formation of a specific polymer called peptidoglycan. Viruses don't have this problem so antibiotics are ineffective against them.
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Specific drugs which work against specific antigens.
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Card 2


What are viruses?


They are very small, between 0.02 - 0.3 micrometers. They are non-living and consist of DNA surrounded by a protein coat. They reproduce by taking over living cells.

Card 3


What are fungi?


Preview of the front of card 3

Card 4


What are protoctists?


Preview of the front of card 4

Card 5


What is a communicable disease?


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