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31 Cards in this Set
- Front
- Back
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How do bacteria cause disease? |
They damage cells or release toxins that are toxic to the host. |
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How do fungi cause damage? |
They can send out specialised reproductive hyphae which grow to the surface of the skin and release spores. |
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How do viruses cause damage? |
They invade cells and take over the genetic machinery and other organelles. They cause the cell to make more copies of the virus, the host eventually bursts and releases many new viruses. |
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How do protoctista cause harm? |
They enter host cells and feed on the contents as they grow. |
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Stages of the lifecycle of a pathogen? |
Moves from one host to another (transmission), enters the host's tissues, reproduces and then leaves the host's tissues. |
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Means of direct transmission? |
Direct physical contact, faecal-oral transmission, droplet infection and transmission by spores. |
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Social factors affecting transmission? |
Overcrowding, poor ventilation, poor diet, poor health, migration and homelessness. |
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A vector is an example of indirect transmission. What is a vector? |
Another organism used by the pathogen to gain entry to the primary host. |
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Direct transmission of plant pathogens? |
Found in soil and infect plant by entering the roots. Fungi produce spores which are carried in the wind and result in airborne transmission. |
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Indirect transmission of plant pathogens? |
Spores or bacteria attach to a burrowing insect. This attacks an infected plant. |
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Physical defences of plants against pathogens (passive)? |
Cellulose cell wall, lignin thickening of cell wall, waxy cuticles, bark, stomatal closure, Callose and Tylose formation. |
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Active defences of plants against pathogens? |
Cell walls are thickened and strengthened by additional cellulose, oxidative bursts produce highly reactive oxygen that damage cells of invading organism, increase in production of chemicals and Callose deposited between cell wall and membrane to prevent penetration at infection site. |
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What's Necrosis and Canker? |
Necrosis is cell suicide- cells surrounding the infection are killed and this limits the pathogens access to water and nutrients. Canker is a sunken necrotic lesion in the woody tissue and causes death of the cambium tissue. |
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How does the skin produce an effective barrier to pathogens? |
The outer layer of skin mainly consists of Keratinocytes. They migrate out to the skins surface and their cytoplasm is replaced by keratin, this is called keratinisation. |
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Primary defences against disease? |
The skin, blood clotting and skin repair, mucous membranes, coughing and sneezing, inflammation. |
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Whats an antigen? |
It's a chemical marker on the membrane of a pathogen so that it can be recognised as foreign. They're proteins of glycoproteins intrinsic to the plasma membrane. |
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What are opsonins? |
They're protein molecules that bind to the antigens and they're a type of antibody. They enhance the ability of phagocytic cells to bind and engulf pathogens. |
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Process of phagocytosis? |
1. Neutrophil binds to the opsonin on the antigen of the pathogen. 2. Pathogen engulfed by endocytosis forming a Phagosome. 3. Lysosomes fuse to phagosome and release lytic enzymes 3. After digestion, harmless products can be absorbed into the cell. |
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How does a macrophage work? |
1. It engulfs the pathogen but doesn't fully digest it. 2. It saves the antigen and moves it to a special protein complex on the surface of the cell. 3. Cell is now an antigen presenting cell and can be recognised by cells of the immune system and so it's not mistaken as foreign. |
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Role of an antigen-presenting cell? |
It moves around the body in order to increase its chances of coming into contact with B and T lymphocytes to activate full immune response and be met by the correct recognition site for the antigen. |
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What is clonal selection? |
Activation of specific B and T cells. This leads to the production of antibodies to combat the pathogen and production of memory cells to provide long term immunity. |
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Function of Cytokines? |
These are hormone-like chemicals that stimulate and coordinate the immune response, involved in cell signalling and communication. They stimulate the differentiation and activity of macrophages, B and T cells. |
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Types of T lymphocytes? |
T Helper cells- release cytokines T killer cells- Kill host body cells T Memory cells- provide long term immunity T Regulator cells- shut down the immune response. |
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Types of B lymphocytes? |
Plasma cells- manufacture and release antibodies B Memory cells- act as the immunological memory |
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What is an autoimmune disease? |
Occurs when the immune system attacks a part of the body- usually, B and T cells specific to our own antigens are destroyed but in this case they start to attack our own antigens. E.g arthritis and lupus |
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What's an antibody? |
An immunoglobulin- a complex protein produced by plasma cells. They attach to antigens and render them harmless |
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Structure of an antibody? |
They're made of 4 polypeptide chains, with two distinct regions. Variable region has a shape specific to the antigen and the constant region is the same in all antibodies. Disulfide bridges hold polypeptides together and the hinge region allows flexibility so the antibody can grip more than one antigen. |
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what is a vaccination? |
A way of stimulating an immune response so that immunity is achieved. |
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Difference between a herd vaccination and a ring vaccination? |
Herd vaccination provides immunity to almost all of the population at risk. Ring vaccination involves vaccinating all people in the immediate vicinity of the new case. |
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Role of agglutinins? |
They cross-link pathogens and clump them together. This makes them easier to engulf and prevents them carrying out their function |
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Role of antitoxins? |
They bind to molecules released by pathogenic cells and they render them harmless as they may be toxic molecules. |
