4.1.1 Flashcards
Give an example of a bacterial plant disease
Ring rot
Give an example of a viral plant disease
TMV
Give 2 examples of fungal plant diseases
Potato blight and black sigatoka
Give two examples of bacterial diseases in animals
Bacterial meningitis and tuberculosis
Give two examples of viral diseases in animals
HIV and Influenza
Give an example of an animal disease caused by a protist
Malaria
Give two examples of fungal diseases in animals
Ring worm and athlete’s foot
What are the types of direct transmission of pathogens between animals?
Direct contact, inoculation, ingestion
Give examples of direct contact
- Kissing or any contact with the body fluids of another person
- Direct skin-to-skin contact
- Microorganisms from faeces transmitted on the hands
Give examples of inoculation
- Through a break in the skin
- From an animal bite
- Through a picture wound or through sharing needles
Give an example of ingestion
Taking in contaminated food or drink, or transferring pathogens to the mouth from the hands
What are the types of indirect transmission?
- Fomites
- Droplet infection
- Vectors
What is a fomite?
An inanimate object that transfers pathogens
What is droplet infection?
When an infected individual talks, coughs or sneezes, the droplets of saliva and mucus may contain pathogens, which infect healthy individuals
What are vectors?
A vector is something that transmits communicable pathogens from one host to another
What factors affect the transmission of communicable diseases
- Overcrowded living and working conditions
- Poor nutrition
- A compromised immune system
- Poor disposal of waste
- Climate change
- Culture and infrastructure
- Socioeconomic factors
What is the main physical defence of plants?
Callose
Describe the effect of callose
- It is synthesised and deposited between the cell walls and the cell membrane in cells next to the infected cells. They prevent pathogens entering the plant cells around the site of infection
- Callose blocks sieve plates in the phloem
- Callose is deposited in the plasmodesmata between infected cells and their neighbours
What are the chemical defences of plants?
- Insect repellents
- Insecticides
- Antibacterial compounds
- Antifungal compounds
- Anti-oomycetes
- Toxins
What barriers exist to prevent the entry of pathogens in humans?
The skin, which contains a skin flora of microorganisms, and sebum, which inhibits growth of pathogens
Mucous membranes
Lysozymes in tears and urine
Describe the process of blood clotting and wound repair
Skin is breached. Platelets reach the collagen in skin and release thromboplastin and thrombin
What does thromboplastin do?
It catalyses the conversion of prothrombin into thrombin, in the presence of Ca+2. Thrombin then catalyses the conversion of fibrinogen to fibrin, which forms a clot
What does serotonin do?
Makes the smooth muscle in the walls of the blood vessels contract, so they narrow and reduce the supply of blood to the area
What is the inflammatory response?
A localised response to pathogens resulting in inflammation at the site of a wound
What cells are activated in damaged tissue?
Mast cells
What do mast cells release?
Cytokines and histamines
What do histamines do?
Make the blood vessels dilate, causing localised heat and redness. Blood vessel walls also become more leaky so blood plasma is forced out
What to cytokines do?
Attract white blood cells to the site.
What are the stages of phagocytosis?
- Pathogens produce chemicals that attract phagocytes
- Phagocytes recognise the non-self antigens
- Phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
- Phagosome combines with a lysosome to form a phagolysosome
- Enzymes from the lysosome digest and destroy the pathogen
What happens when a macrophage digests a pathogen?
It becomes an APC (antigen presenting cell)
What are the two types of phagocytes?
Neutrophils and macrophages
Which type of phagocyte has a multi-lobed nucleus?
Neutrophil
What are opsonins?
Antibodies that tag antigens to make it easier for the macrophages to engulf the pathogens
What are the two different types of lymphocytes?
T lymphocytes and B lymphocytes
What happens at the start of the cell-mediated response?
Specific T helper cell binds to the APC. The T helper cell releases interleukins (a type of cytokine)
What do the interleukins cause?
They cause the T helper cells to start dividing by mitosis and specialise into other types of cells?
What cells do the T helper cells specialise into?
T memory cells, T killer cells, T regulatory cells
What happens at the start of the humoral response?
A B cell with the specific antibody shape for the antigen binds to the antigen and becomes an APC. The B cell APC then binds to a T helper cell. This is clonal selection
What is clonal expansion?
When the B cell divides by mitosis and specialises into other types of B cells. The main two types are B memory cells and B plasma cells
What do the B plasma cells do?
They make even more B plasma cells, which produce antibodies specific to the antigen
How are the heavy chains and light chains on antibodies linked?
By disulfide bridges
How many antigens can each antibody bind to?
2
What are the different functions of antibodies?
- Act as agglutinins, sticking the pathogens together, making phagocytosis easier
- Act as opsonins, tagging antigens
- Act as antitoxins
- Directly attack pathogens
