Module 4: Disease and the Immune system Flashcards
What is a disease?
A condition that impairs the normal functioning of an organism.
What is a communicable disease?
A disease that spreads from organism to organism.
Name an animal disease caused by bacteria.
•tuberculosis
•bacterial meningitis
Name a plant disease caused by bacteria.
Ring rot
(potatoes, tomatoes)
Name an animal disease caused by fungi.
•ringworm
•athlete’s foot
Name a plant disease caused by fungi.
Black Sigatoka
(banana plants)
Name a disease in plants caused by protoctista.
Potato/tomato late blight.
Name an animal disease caused by protoctista.
Malaria
Name a plant disease caused by a virus.
Tobacco mosaic virus
Name an animal disease caused by a virus.
•HIV/AIDs
•influenza
Give an example of direct transmission.
Droplet transmission (coughing/sneezing).
What is direct transmission?
When the pathogen is spread directly from one organism to another.
What is indirect transmission?
When the pathogen is spread though something else.
Give an example of indirect transmission.
Though air, water, food.
What is a vector?
Anything that carries the pathogen from one host to the next.
What is a non-specific defence?
Something that prevents pathogens entering the body. They are the same for all pathogens.
Give some examples of non-specific defences in humans.
*skin
*mucous membranes
*tears
*stomach acid
*blood clotting
*wound repair
*expulsive reflexes
*inflammation
How does the skin act as a defence against pathogens?
*physical barrier
*layer of dead skin cells - hard for pathogens to penetrate
*sebaceous glands secrete sebum (slightly acidic) - prevents growth of harmful bacteria
*covered with harmless microorganisms - compete for resources - reduce growth of pathogens
What are lysozymes?
Enzymes that destroy bacteria by digesting their cell walls.
How do mucous membranes act as a defence against pathogens?
*line openings
*secrete mucous - traps microorganisms to be destroyed by phagocytes
*contain lysozymes
How do tears act as a defence against pathogens?
They contain lysozymes.
How does the stomach acid act as a defence against pathogens?
Hydrochloric acid kills pathogen’s in food and water - pH too high.
What are expulsive reflexes?
The body’s automatic responses to irritation to remove foreign bodies.
Give some examples of expulsive reflexes.
*sneezing
*coughing
*vomiting
*diarhhoea
What is a blood clot?
A mesh of protein fibres (fibrin).
How do blood clots as a defence against pathogens?
Plug wounds to reduce blood loss prevent pathogens entering.
How are blood clots formed?
*when the endothelium gets damaged, platelets become exposed to proteins outside of this
*this activates the platelets, which form a plug and release clotting factors
How does wound repair happen?
*outer layer of skin cells divide and migrate to edges of wound
*the tissue below contracts and brings the edges closer
*collagen fibres repair the wound
What are signs of inflammation?
*swelling
*redness
*pain
*heat
How does inflammation occur?
*damaged tissue activates mast cells which release histamines
*this causes vasodilation, to increase blood supply, which brings more white blood cells to the area and also increases temperature, so pathogens have less ability to reproduce
*histamines also make blood vessel walls more permeable, so more plasma leaves forming more tissue fluid, causing swelling and pathogens to be isolated
How does the waxy cuticle act as a defence against pathogens?
*physical barrier that is hard for pathogens to penetrate
*prevents water collecting on the leaves, so reduces the chance of infection by antigens carried in water
How do cell walls act as a defence against pathogens?
They are a physical barrier that make it harder for pathogens to enter cells.
What is callose?
A polysaccharide produced by plants that is deposited between cell walls and plasma membranes.
When is callose deposited?
In times of stress, e.g. during pathogen invasion.
How does callose act as a defence against pathogens?
*makes it harder for pathogens to enter cells
*when deposited in the plasmodesmata, it limits the spread of viruses between cells
What are plasmodesmata?
Small channels in plant cell walls.
Give some examples of chemical plant defences against pathogens.
*antimicrobial chemicals
*chemicals that are toxic to insects
How do chemicals secreted by plants act as a defence against pathogens.
*kill pathogens
*inhibit pathogen growth
*prevent infection by insect vectors
What are antigens?
Molecules found on the surface of cells.
What is meant by non-specific responses?
They happen in the same way for all microorganisms.
What is meant by specific responses?
They are antigen-specific, so only work for specific pathogens.
What are the 2 types of white blood cells?
Lymphocytes and phagocytes.
What are the 2 types of lymphocytes?
B and T lymphocytes.
Are lymphocytes involved in the specific or non-specific immune response
Specific.
What are the 2 types of phagocytes?
Macrophages and neutrophils.
Are phagocytes involved in the specific or non-specific immune response?
Non-specific (apart from macrophages - sometimes specific.
Where are phagocytes found?
In the blood and in tissues.
What are opsonins?
Molecules in the blood that attach to foreign antigens to aid phagocytosis.
What is one way in which opsonins work?
Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively charged phagocyte to get closer to the pathogen.
What is a phagosome?
A vesicle inside a phagocyte, containing the pathogen.
What is a lysosome?
An organelle containing digestive enzymes.
Which white blood cell responds to pathogens first?
Neutrophils.
What are cytokines?
Proteins that act as messenger molecules.
Describe phagocytosis.
*damaged cells and pathogens release cytokines, attracting phagocytes
*opsonin proteins attach to pathogen and mark them
*phagocytes have receptors which attach to chemicals on pathogens
*phagocytes engulfs pathogen, forming phagosome
*lysozymes hydrolyse pathogen
What happens after phagocytosis in macrophages?
The macrophage presents the pathogen’s antigens on its surface to activate other immune cells, becoming an APC.
What happens after phagocytosis in neutrophils?
The products of the digested pathogen are absorbed in the cell, or secreted by exocytosis.
What is clonal selection?
Specific receptors on T lymphocytes bind only to specific antigens.
What is clonal expansion?
T lymphocytes with the complementary receptors divide by mitosis to produce clones.
What is the cell-mediated response?
The response involving T lymphocytes, only activated by antigens on APCs.
What do T helper cells do after cloning?
*activate B lymphocytes
*stimulate macrophages
*become memory cells
*become cytotoxic T cells
How do cytotoxic T cells ‘kill’ cells?
They release perforin, which makes holes in the cell’s plasma membranes meaning any substances can enter of exit, so the cell dies.
What cells do cytotoxic T cells kill and why?
Its own body cells in order to prevent pathogens dividing in them.
What are two ways pathogens can cause harm?
*directly damaging tissue
*release of toxins
How do hot climates increase transmission?
*more kinetic energy for chemical reactions
*pathogens reproduce more rapidly
What social factors can increase transmission?
*poor sewage infrastructure
*lack of freshwater
*poor sanitation
*overcrowded living
*medicine and vaccines less readily available
What are the three types of direct transmission in animals?
*direct contact
*innocluation
*ingestion
Give an example of direct contact.
Kissing.
Give an example of inncoluation.
*animal bites
*sharing needle
Give an example of ingestion.
Contaminated water.
What are the three types of indirect transmission in animals?
*vectors
*droplets
*fomites
Give an example of a vector.
Mosquito.
Give an example of droplets.
Saliva/sneezing.
Give an example of fomites.
Dirty bedding.
How can direct transmission occur in plants?
Direct contact of other plants.
What are the two ways indirect transmission can occur in plants?
*contaminated soil
*vectors
What are the types of plant defences against pathogens?
*barriers (waxy cuticle, bark)
*antibacterial chemicals (repel insects and kill pathogens)
*physical defences (prevent pathogens spreading - callose)
What happens to the pathogen after it has been hydrolysed?
*useful soluble molecules are absorbed in cytoplasm
*antigens are presented on surface of phagocyte
Is the second line of defence specific or non-specific?
Specific.
Where are T and B lymphocytes made?
Bone marrow.
Where do T lymphocytes mature?
Thymus.
Where do B lymphocytes mature?
Bone marrow.
What is the humoral response?
The immune response involving B cells and antibodies.
What are the three roles of antigens?
*agglutination
*mark pathogens
*anti-toxins
What is agglutination?
Antibodies clumping pathogens together.
What do anti-toxins do?
Bind to toxins to prevent them entering the cell.
What are the two types of B cells?
*plasma cells
*B-memory cells
What do plasma cells do?
Produces antibodies.
What do memory cells do?
*remain in blood and recognise pathogens on reinfection
*divide rapidly into plasma cells to make antibodies
What is an epidemic?
When a disease spreads rapidly on a national level.
What is a pandemic?
When a disease spreads rapidly on a global level.
What is herd immunity?
When a large percentage of the population is vaccinated, meaning people who can’t have it are still protected.
How do antibodies kill bacteria?
*prevent cell wall synthesis (inhibit enzymes responsible for making molecules in a cell wall)
*disrupt cell membranes (bind to phospholipids)
*interfere with protein synthesis in bacteria
Explain the process of antibiotic resistance.
*random mutations in bacterial genetic material
*could code for new proteins, providing selective advantages
*reproduce with these advantages
What increase antibiotic resistance?
Overuse and misuse of antibiotics.
What is personalised medicine?
Medicines that are tailored to an individual’s DNA, using genetic information.
What is synthetic biology?
Using technology to make things such artificial proteins, cells and microorganisms.
