communicable diseases SLOP Flashcards
State the kingdom of organism that causes each of the following diseases: tuberculosis, Black Sigatoka, Athlete’s foot, malaria
Bacteria, fungi, fungi, protoctists
State the kingdom of organism that causes each of the following diseases: blight, ringworm, ring rot, bacterial meningitis
Protoctists, fungi, bacteria, bacteria
Give one plant disease caused by each of the following: viruses, bacteria and fungi
Tobacco mosaic virus, ring rot, black sigatoka
State three factors that would affect the speed of disease transmission in plants
Overcrowding; poor mineral nutrition; damp, warm, humid conditions; climate change
State how the influenza virus is most likely to be transmitted between different humans
Respiratory droplets (inhalation)
State four different types of vector that can be used to transmit a communicable disease
Water (e.g. diarrhoeal diseases); animals (e.g. mosquito transmits Plasmodium); wind (carries spores); humans (hands, clothing etc.)
State three passive physical defences that prevent plants being infected by a pathogen
Bark, waxy cuticle, thorns, spines, lignified cell walls, cellulose etc.
State three active physical defences a plant would employ against an invading pathogen
Callose synthesised and deposited between plasma membrane and cell wall; callose blocks sieve plates in phloem; callose deposited in plasmodesmata between infected cells and their neighbours; lignin added to cell walls; tyloses block xylem vessels
State three chemical defences a plant would employ against an invading pathogen
Antibacterial compounds like phenols, alkaloids; terpenes; hydrolytic enzymes like glucanases and chitinases; caffeine; tannins etc.
Describe the role of the skin as a primary non-specific defence
Dead outer layer of keratin prevents pathogen entry; skin flora outcompete pathogens for space; oil secretions inhibit pathogenic growth
Describe the role of mucous membranes as a primary non-specific defence
Mucus traps pathogens and contains lysozymes; phagocytes engulf and digest pathogens in mucus
Which enzyme catalyses the conversion of prothrombin to thrombin
Thromboplastin (thrombokinase)
Describe the role of thrombin in the clotting process
Causes the conversion of soluble fibrinogen into insoluble fibrin fibres
Describe the process of inflammation as a secondary non-specific response
Mast cells release histamines; histamines increase permeability of capillaries meaning plasma leaks into tissue fluid (pain and swelling); vasodilation of arterioles so more blood reaches infected area (heat and redness); neutrophils attracted to area for enhanced phagocytosis
Describe the process of phagocytosis
Phagocyte engulfs pathogen into a phagosome; lysosomes fuse with phagosome to form a phagolysosome; enzymes, hydrogen peroxide and nitric acid break down the pathogen
Describe how macrophages process antigens for presentation on their cell surface membrane
Antigen fragments combined with MHC (special glycoproteins in cytoplasm)
What name is given to small protein molecules that act as cell-signalling compounds?
cytokines
Describe how neutrophils are specialised for their role
Plasma membrane contains receptors for opsonins, well developed cytoskeleton for phagocytosis, many mitochondria for respiration, many ribosomes to make enzymes, many lysosomes, many Golgi
Opsonins are non-specific. Explain why
Opsonins can attach to many types of pathogen and help the process of phagocytosis, by giving the phagocyte something to bind to. They must be non-specific, so they can attach to many different pathogens.
Where do B lymphocytes and T lymphocytes mature?
Bone marrow and thymus respectively
What is meant by the term ‘autoimmunity’ and give two examples of autoimmune diseases
Destruction of self-tissue; rheumatoid arthritis, lupus, type I diabetes
What is the role of T regulatory cells?
Dampen down the immune response; prevents destruction of self tissue (autoimmunity)`
Describe how an antigen presenting cell leads to large numbers of T helper cells
APC binds specifically to a T helper cell (clonal selection). This selected T helper cell then proliferates by mitosis (clonal expansion)
Describe how B lymphocytes are activated and the role of activated B lymphocytes
The cell binds specifically to B lymphocyte; B lymphocyte differentiates into a plasma cell. Plasma cells release antibodies specific to the particular antigen
Describe how T killer cells destroy a virally infected cell
Release perforins which punch holes in the membrane of the cell; T killer cell inserts channels through which it floods hydrogen peroxide/nitric acid/hydrolytic enzymes
Distinguish clearly between an antigen and an antibody
An antigen is a cell-surface molecule that is specific to the cell (and a particular antibody); an antibody is an immunoglobulin manufactured by the plasma cells (which binds specifically to an antigen).
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role
Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and mitochondria.
Describe how opsonins function
Opsonins bind specifically to an antigen on a pathogen (via the variable region), clearly marking the pathogen for destruction by a neutrophil. A neutrophil will bind to the constant region of the opsonin and destroy the pathogen by phagocytosis
Describe how agglutinins function
Agglutinins cross link pathogens by binding specifically via their variable regions. Pathogens are clumped together (agglutinated), meaning they cannot enter host cells and are easier to phagocytose
Describe how antitoxins function
Neutralise toxin molecules released by a pathogen through direct binding
Describe how the structure of an antibody enables it to perform its function
- The variable region is specific to the antigen
- it has a shape that is complementary to the shape of the antigen
- the disulfide bridges hold the four polypeptide chains together
- the hinge region allows some flexibility so that the molecule can bind to more than one antigen
- the constant region may have a shape that can be recognised by the neutrophils.
Explain why it may take several days for the primary immune response to become effective
After infection, the pathogen must be detected and attacked by macrophages; antigen presentation occurs to select the correct B and T cells (clonal selection); these cells must reproduce in clonal expansion; then they must differentiate to form plasma cells; the plasma cells must start to produce the antibodies – each step takes time.
Explain why a secondary immune response is so much faster than a primary immune response
B memory and T memory cells are circulating in the blood. On second encounter with a pathogen, the correct B/T memory cell is clonally selected and can very quickly differentiate into correct specific T helper/T killer/plasma cell. Plasma cells can produce antibodies faster, sooner and in much greater quantity. Pathogens are wiped out before symptoms are experienced; level of antibody stays higher for longer
Give an example of both natural active immunity and natural passive immunity
Natural active - antibodies made by immune system in response to infection; natural passive - antibodies provided via placenta/breast milk (useful in developing immune system)
Explain why passive immunity only provides short-term immunity
Passive immunity is provided by an external supply of antibodies – these are proteins and will not last long in the body. They may even act as antigens and be attacked by antibodies from our immune system.
Give an example of artificial active immunity
Immunity provided by antibodies made in response to vaccination (dead/inactive pathogens injected)
Define the term epidemic
A rapid spread of disease through a high proportion of a population (usually within a country)
Describe the difference between herd vaccination and ring vaccination
Herd vaccination is where everyone, or almost everyone, is vaccinated. Ring vaccination is vaccinating people around the site of the outbreak, so that the pathogen will not be transmitted across that ring to the whole population.
Describe how a microorganism can become resistant to an antibiotic
Bacteria that survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a selective force which selects the resistant individuals. When they reproduce, some of their offspring may be more resistant, thus resistance evolves.
what is the difference between b cells and t cells
- T cells are responsible for cell-mediated immunity.
- B cells, which mature in the bone marrow, are responsible for antibody-mediated immunity.
- The cell-mediated response begins when a pathogen is engulfed by an antigen-presenting cell, in this case, a macrophage.
