Disease Flashcards
What are the types of pathogens?
Bacteria, fungi, protoctista and virus
What are the different shapes of bacteria?
Rod, chain, coccus, pair of cocci, cluster of cocci, comma shaped, spiral, corkscrew
How can bacteria be classified?
Shape or cell wall
How can bacteria be classified by their cell wall?
Gram staining - gram positive (purple-blue) or gram negative (red)
Name an example of a gram positive and a gram negative bacteria
Gram positive: MRSA
Gram negative: E.coli
What are the properties of viruses?
0.02-0.3 micrometers, 50x smaller than bacteria, reproduce within host cells
What are the properties of protoctista?
Eukaryotic, single celled or multicellular, use host cells to reproduce
What are the properties of fungi?
Eukaryotic, often multicellular, often saprophytes (eats dead matter), some are parasitic
How do viruses infect cells?
Inject viral genetic material into host cell (and so host DNA), virus then uses the host cell to make new virus cells, which causes cell lysis
How do protoctista infect cells?
Use host cells to reproduce and the cause cell lysis, but does not take over host cell’s DNA. Digest and use cell contents as they reproduce
How do fungi infect cells?
Digest living cells and destroy them
How do bacteria infect cells?
Produce a poison that damages host tissues, either by breaking down cell membranes, inactivate enzymes or damage host cell’s genetic material so the cells cannot divide
What are the outcomes of plant diseases?
Starvation, loss of jobs (so failing economy) and danger to ecosystems
Name an example of a plant bacterial disease
Ring rot (gram positive) Symptoms include: damages leaves, tubers and fruit
Name an example of a plant viral disease
Tobacco mosiac virus
Symptoms: Damages leaves and fruit, stunts growth and yield
Name an example of a plant disease caused by a protoctista
Potato blight (tomato/late blight) Symptoms: Destroys leaves, fruit and tubers
Name an example of a plant fungal disease
Black sigatoka
Symptoms: Destroys leaves (turning them black), reduced yield
Name an example of an animal bacterial disease
Tuberculosis (TB, mycobacterium tuberculosis)
Symptoms: Damages lung tissue, suppresses immune system
Name an example of an animal viral disease
HIV/AIDS
Symptoms: more susceptible to other diseases
Name an example of an animal disease caused by a protoctista
Malaria (vector of mosquitos)
Symptoms: rolling fevers
Name an example of an animal fungal disease
Ring worm
Symptoms: Grey-white, crusty circular areas of skin
How are diseases spread?
Indirect and direct transmission
What are some examples of direct transmission in animals?
Direct contact, inoculation, ingestion
What are some examples of indirect transmission in animals?
Fomites (inanimate objects like bedding, socks), droplet infection, vectors
What are some of the factors affecting the transmission of disease in animals?
Overcrowding, malnutrition, poor immune system, little/no waste disposal, climate change, culture and infrastructure, socioeconomic factors
What are some examples of direct transmission in plants?
Direct contact between parts of a healthy plant with parts of a diseased plant
What are some examples of indirect transmission in plants?
Soil contamination, vectors
Name some examples of vectors for indirect disease transmission in plants
Wind, water, animals and humans
What are some of the factors affecting the transmission of disease in plants?
Susceptible plant breeds, over-crowding, poor mineral nutrition, damp/warm conditions, climate change
How do plants prevent disease?
- pathogen recognised by glycolipid
- and compounds of broken down cell wall from pathogenic enzymes are recognised
- signalling molecules alert plant cell’s nucleus
- nucleus triggers production of callose and lignin to block plasmodesmata to prevent pathogen entering
- chemical is secreted to alert other plant cells
What are the properties of plants physical defence?
Polysaccharide with beta 1-3 and 1-6 glycosidic bonds between glucose monomers
What are some chemical defenses in plants?
Insect repellents (pine resin), insecticides, antibacterial compounds, antifungal compounds (chitinases), anti-oomcytes (glucanases), general toxins
What are some non-specific defenses in animals? (keep out)
Skin, mucus, tears/stomach acid, blood clotting, inflammation, expulsive reflexes
How is skin a non-specific defense? (keep out)
Covers areas of body to prevent pathogens entering, skin flora of microorganisms to outcompete, sebum (oil) to inhibit growth of pathogens
How is mucus a non-specific defense? (keep out)
Sticky to trap pathogens, contains lysozymes to digest pathogens
How are tears/stomach acid a non-specific defense? (keep out)
Lysozymes (also applies to urine)
How are expulsive reflexes a non-specific defense? (keep out)
Expulsive reflexes (sneezes, coughs, vomiting and diarrhoea) expel contents of body that may contain pathogens
How is blood clotting a non-specific defense? (keep out)
Blood clots seal a wound that pathogens may enter by
What is the cascade response for blood clotting?
1 - injury
2 - Platelets aggregate
3 - Triggers the release of serotonin and thromboplastin
4 - Serotonin causes muscles to contract for ease of clot formation
5 - Converts inactive prothrombin into active thrombin
6 - Active thrombin converts fibrinogen into fibrin (collagen fibers)
How is inflammation a non-specific defense? (keep out)
Histamines make blood vessels dilate, which causes heat to prevent pathogens reproducing. Histamines also cause blood plasma to move out of the vessels (tissue fluid) which causes swelling and pain. Cytokines attract white blood cells to the site to dispose of the pathogens via phagocytosis
What are some other non-specific defenses in animals? (getting rid)
Fevers and phagocytosis
How are fevers a non-specific defense? (getting rid)
Pathogens cannot reproduce at a higher temperature (most often above 37 degrees) and specific immune system works faster at higher temperatures (caused by cytokines)
What is phagocytosis?
A process where specialised white blood cells (phagocytes) engulf and destroy pathogens (neutrophils and macrophages)
List the stages of phagocytosis
1 - Pathogens produce chemicals that attract phagocytes
2 - Phagocytes recognise foreign proteins on the pathogen
3 - Phagocyte engulfs pathogen and encloses it in a vacuole called a ‘phagosome’
4 - The phagosome combines with the lysosome to form a phagolysosome
5 - Enzymes from the lysosome digest and destroy the pathogen
What are cytokines?
Act as cell-signaling molecules that alert other phagocytes that there are foreign bodies within the organism. Can also increase body temperature
What are opsonins?
Chemicals that bind to pathogens and ‘tag’ them so they can be more easily recognised by pathogens. Phagocytes have receptors in their plasma membranes that are complementary to common opsonins
What are antibodies?
Molecules that bind to foreign antigens so the immune system know which cells to attack, form an antigen-antibody complex when binds to antigen
What is the structure of antibodies?
Light chain, heavy chain, variable and constant region, receptor binding site and antigen binding site (and flexible hinge regions)
How do antibodies defend the body?
1 - antigen-antibody complex acts as an opsonin
2 - Antigen-antibody complex makes it difficult for pathogens to invade host cells
3 - Antigen-antibody complex causes pathogens also carrying the complex to clump together, so acts as an agglutinin
4 - antibodies bind to toxins produced and so makes them harmless
What are lymphocytes?
Specialised white blood cells, come as B and T lymphocytes
Where are lymphocytes made?
B - Bone marrow
T - Thymus gland
What are the different types of T lymphocytes?
T helper, T killer, T memory and T regulator
What are the different types of B lymphocytes?
Plasma cells, B effector and B memory
What is the function of T helper cells?
Bind to pathogen’s plasma membrane and produce interleukins (a form of cytokine) to stimulate the activity of B lymphocytes to increase antibody production and other T lymphocytes
What is the function of T killer cells?
Produces perforin, which kills the pathogen by making holes in the plasma membrane
What is the function of T memory cells?
Live for a long time in the blood (immunological memory) and divide rapidly into T killer cells when in contact with the pathogen again
What is the function of T regulator cells?
Interleukins are involved in supressing the immune system to regulate and prevent host antigens being attacked
What is the function of plasma cells?
Produce antibodies that are complementary to antigens (can produce 2000 antibodies per second)
What is the function of B effector cells?
Divide to form plasma cell clones
What is the function of B memory cells?
Live for a VERY long time (immunological memory) and have a very specific response when a specific foreign antigen enters the host again
What is the difference between cell-mediated and humoral immunity?
Cell mediated: pathogens/changes within cells
Humoral immunity: responds to antigens found outside of host cells
In humoral immunity, what is a primary and secondary immune response?
Primary immune response: slower, first response
Secondary immune response: very quick, no symptoms
What is an autoimmune disease?
When the immune system confuses self-cells with foreign cells and so attacks healthy body tissue
Name some examples of autoimmune disease
Type 1 diabetes, rheumatoid arthritis, lupus
