Communicable Diseases Flashcards
Describe Bacteria (3 points)
Where are they normally found in plants?
reproduce rapidly
damage cells
releases waste products (toxins)
vascular tissues (cause blackening and death)
Describe Fungi (3 points)
Where is it normally found in plants?
What does it do?
lives under skin of animal
hyphae which form mycelium, grow under skin surface
send out reproductive hyphae that grow to skin’s surface and release spores
in vascular tissues where it gains nutrients
the hyphae release enzymes to digest the tissue which causes decay
Describe Viruses (3 points)
invade cells and take over genetic machinery and organelles
cause cell to make copies of virus
host cell bursts releasing them
Examples of bacteria
tuberculosis
bacterial meningitis
ring rot
Examples of fungi
black sigatoka (leaf spots on banana plant ring worm (cattle)
Examples of viruses
HIV/AIDS
influenza
tobacco mosaic virus
Describe Protoctista (2 points)
enter host cell
feed on contents
Examples of protoctista
blight
Malaria (plasmodium) - feed on haemoglobin in RBC
What is the transmission of pathogens?
when they travel from one host to another
What is DIRECT TRANSMISSION?
passing a pathogen between hosts without intermediary
What are 4 types of direct transmission
1) physical contact - HIV, meningitis, athlete’s foot
2) faecal (oral - food/water) - cholera, food poisoning
3) droplet infection - tuberculosis, influenza (sneeze)
4) spores (in air, surfaces, soil) - tetanus
What is INDIRECT TRANSMISSION?
passing on pathogens with a vector (organism that carries pathogen between hosts)
e.g. plasmodium enters via bite from female mosquito
Direct transmission in plants?
Indirect transmission?
pathogens in soil
fungi produce spores by reproduction then carried in wind
pathogen in leaves return to soil when shed
enter fruit or seed so offspring infected
insect attach and spores/bacteria attach to insect which carries pathogen away
What is a PASSIVE DEFENCE against pathogens?
present before infection, prevents entry or spread of pathogen
What are 7 physical passive defenses of plants?
1) cellulose cell wall (contains chemicals)
2) lignin thickening of cell walls (waterproof indigestible)
3) waxy cuticle (pathogens need water)
4) bark (chemicals)
5) stomatal closure (stop entry)
6) callose (blocks flow, deposited in sieve tubes)
7) tylose (swelling fills xylem to prevent spread in water, also contains chemicals that toxic to pathogens)
What are 2 chemical passive defences of plants?
Why are there not many chemicals present before infection?
chemicals have anti-pathogenic properties
1) terpenes in tyloses
2) tannins in bark
producing them takes energy
What are 6 active defences on plants?
1) fortify defences present
2) thicken/strengthen walls (cellulose)
3) callose between wall and membrane near pathogen - prevent entry
4) oxidative bursts (oxygen damage pathogen)
5) necroses (cell suicide near infection, stop spread)
6) canker (sunken necrotic lesion in woody tissues that causes death of cambium tissue in bark)
How does the skin act as a primary defence mechanism against disease?
the epidermis (outer surface) consists of keratinocytes which are produced by mitosis at the base of the epidermis then move up to the surface. They dry out and the cytoplasm is replaced by keratin. This is keratinisation which creates dead cells on the surface that act as a barrier.
What does blood clotting require?
calcium ions and at least 12 clotting factors which are released from platelets and damaged tissue. They activate the enzyme cascade.
Describe the process of how a blood clot forms.
1) damage to blood vessel exposes collagen fibres
2) platelets are activated and create temporary plug
3) platelets and damaged cells produce thrombokinase (protein)
4) this activates an enzyme which converts prothrombin (protein) to thrombin (enzyme)
5) thrombin catalyses soluble fibrinogen to insoluble fibrin
6) fibrin combines and forms mesh
7) mesh traps platelets and RBC
8) CLOT
What happens after a clot is formed?
it dries out into a scab, shrinks and draws sides of the cut together and skin is repaired underneath
stem cells in epidermis divide and migrate to edges of cut
new blood vessels grow to supply oxygen and nutrients to the new tissue
Where are mucous membranes needed?
at exchange surfaces where the surface is thin and less protected
What layer is involved with mucus and what does it do?
What cells are involved?
epithelial layer contains goblet cells which secrete mucus which traps pathogens
ciliated cells move mucus to the top of the trachea to be swallowed (pathogen killed by stomach acidity)
Describe Inflammation:
which cells detect MO?
what effects does the chemical they release have?
what happens to excess tissue fluid?
Mast cells detect presence of MO in tissue, they release histamine (cell signalling substance)
Histamine causes vasodilation and make capillary walls more permeable to WBCs. Blood plasma and phagocytic WBCs leave blood and enter tissue fluid. This causes increased production of tissue fluid which causes swelling (oedema)
Excess tissue fluid is drained to lymphatic system where lymphocytes. Lead to pathogens coming into contact with lymphocytes and causing specific immune response
Opsonins
type of antibody
proteins that attach/bind to antigen on pathogen, allow phagocytes to bind and engulf pathogen
some not very specific, some produced as part of specific immune response
What is neutralisation?
opsonins bind to antigen of pathogen that is a binding site used for attachment to host cells
opsonin renders antigen useless
opsonin assists in phagocytosis but also prevents pathogen entering host cell
What are neutrophils?
phagocyte multi-lobed nucleus manufactured in bone marrow travel in blood and squeeze out into tissue fluid short lived released in large numbers when infection contain large number of lysosomes engulf digest pathogens
Macrophages
larger cells manufactured in bone marrow travel in blood as monocytes many found in lymph nodes where mature into macrophages engulfs pathogens becomes antigen-presenting cell
Antigen-presenting cell
antigen moved to surface of cell after digesting pathogen
special protein complex on surface makes sure not mistaken for foreign cell and attacked
cell moves around body to come in contact with specific T or B lymphocytes
Clonal selection
activation of specific T and B cells
leads to production of antibodies
cytokines
stimulates differentiation and activity of macrophages, B cells, T cells
used in cell signalling
T lymphocytes differentiate into…
T helper cells release cytokines that stimulate B cells (to develop) and phagocytosis
T memory cells provide long-term immunity
T killer cells kill host body cells that display antigen
T regulator cells shut down immune response after success and prevent autoimmunity
B lymphocytes develop into 2 cells
plasma cells in the blood make and release antibodies
B memory cells remain for years and act as immunological memory
Examples of communication using cytokines
macrophages release monokines which attract neutrophils by chemotaxis and stimulate B cells
T cells and macrophages release interleukins which stimulate clonal expansion (proliferation) and differentiation (of B+T)
many release interferon which inhibits virus replication and stimulates T killer cells
The specific immune response consists of 3 stages
activation - clonal selection
clonal expansion - proliferation
differentiation
Activation - clonal selection
to trigger immune response, T + B lymphocytes (with receptor molecules on plasma membrane complementary to antigen) need to detect antigen (in lymph nodes or antigen-presenting cell) then this is correct lymphocyte with correct receptor so replicates
Clonal expansion - proliferation
correct lymphocytes activated and increase in numbers to be effective (by mitotic cell division)
Differentiation
lymphocytes don’t manufacture antibodies directly
clones of lymphocytes develop into range of useful cells
antigens are usually…
proteins or glycoproteins in plasma membrane of pathogen
antibodies are ____________ which are…..
immunoglobins
complex proteins produced by plasma cells
have region with shape complementary to particular antigen
structure of antigen
Y-shaped
2 distinct regions
4 polypeptide chains
disulfide bridges to hold polypeptides (s-s)
hinge region allows flexibility and grips more than one antigen
light polypeptide chain is the variable region with the specific shape
heavy polypeptide chain is the constant region and the same in all antibodies, may have site for easy binding of phagocytic cells
Agglutinins
cross-link pathogens
antibody has 2 binding sites so bind to 2 antigens , clump together (agglutinate) and prevent pathogen from carrying out some functions, can easily be engulfed by phagocytes
Anti-toxins
bind to toxins released by pathogens and render harmless
