Pathogens Flashcards
What is a passive defence
Examples in plants
Plant defence that is continually present
Physical
- Cell wall- physical barrier
- Bark- physical and chemical barrier
- Waxy cuticle- water accumulation, protects entry of pathogens
- Lignin- entry of insects, impermeable
- Stomata- open and close- prevent entry of pathogens
- Callose phloem plug
- Tylose xylem plug
What is a acitve defence?
Examples in plants
Plant defence that is only produced when a pathogen is present.
Blood clotting process
(blood clotting also known as)
Coagulation
When tissue is damaged, it exposes collages in skin or on the walls of the damaged blood vessel.
When platelets come into contact with this collagen, they bind to it and become activated, by releasing chemicals called clotting factors.
One of these clotting factors are thromboplastin.
The thromboplastin, along with calcium ion sin the blood, now catalyse and aid the formation of prothrombin into thrombin (an enzyme)
Thrombin now catalyses the formation of soluble fibrinogen in plasma to insoluble fibrin
The fibrine forms a mesh around the platelets and traps red blood cells, forming a blood clot, or thrombus.
The activated platelets also release serotonin, which causes the smooth muscle cells in the blood vessels to contract, which narrows the blood vessel and reduces the amount of blood to the area.
Phagocytosis
Pathogen releases chemicals which attracts phagocytes. The phagocyte identifies the pathogen as non-self and engulfs it.
This forms a phagosome. The lysosomes in the phagocyte move towards the phagosome and combines with it, forming a phagolysosome.
Here, enzymes break down the pathogen.
After, the pathogen is absorbed by the phagocyte and the antigens combine with MHC in the cytoplasm.
(Only in macrophages, not neutrophils)- The MHC/antigen complex is displayed on the phagocyte membrane, making and antigen-presenting cell.
Humoral response
1) Clonal selection- B cell with complimentary antibody to the pathogen’s antigen will bind to the pathogen and engulf it.
2) B cell becomes antigen presenting cell as it presents the antigen-antibody complex on the cell surface membrane.
3) T- helper cells recognise the antigen presenting B-cell and become activated, releasing cytokines called interleukins.
4) These interleukins stimulate the clonal expansion of B-cells.
5) The B-cells either divide into plasma cells, which secrete antibodies that are specific to the antigen that has entered the body.
6) Can also differentiate into B-memory cells. (Secondary response). When the pathogen re-enters the body, B memory cells can trigger a response to produce high concentration of antibodies over a short period of time.
Cell mediated response
1) After a macrophage has engulfed a pathogen, it becomes an APC.
2) A CD4 receptor on a T-helper cell attaches to the antigen-MHC complex on the APC.
3) T-helper cells release interleukins, which can:
* stimulate phagocytosis.
* stimulate the clonal expansion of B cells
* Can stimulate T-helper cells to divide by mitosis to form T-killer and T-memory cells
4) The T killer cells release perforin, which forms holes in the cell membrane, destroying the infected cell.
5) The T memory cells can later differentiate into T-killer cells if body is infected with same pathogen again.
6) There are also T regulatory cells, which down regulate the immune system once a pathogen is destroyed, and stops the immune system from attacking self-antigens.
When there is a second exposure to the antigen, the antibodies produced are:
In the primary response, there is delay as:
Longer lasting, produced quicker, produced in greater amount.
Clonal expansion and selection must occur, however, in the secondary response, clonal expansion and selection are not required.
Natural immunity meaning
Artifical immunity meaning
Passive immunity meaning
Active immunity meaning
Natural- produced through nromal human processes (no deliberate exposure)
Artificial- produced through deliberate exposure
Passive- Own body does not actively produce its own antibodies or an immune response.
Active- Own body actively produces its own antibodies or an imune response.
Autoimmune disease
Example and way to solve it
When body no longer recognises own cells as ‘self’ and attacks healthy tissue.
Type 1 diabetes- B cells are attacked, unable to produce insulin so high bloof sugar
Immunosuppressant drugs, pancreas transplant or insuli injections.
Pharmacogenomics definition
Synthetic biology definition
Example
Combining personal genetic information with drug action
Synthetic biology is where bacteria and other pathogens are genetically engineered to synthesise large quantities of drug molecules.
Nanotechnology- where non-natural particles deliver drugs to specific areas of the body
Selective toxicity definition
Antibiotics affect the metabolism of bacterial cells, but not human cells.
Antibiotic resistance:
Antibiotic resistance reduced by:
Examples of antibiotic resistant bacteria
When a mutation occurs in a gene, causing a bacteria to be antibiotic resistant. This can survive to reproduce and mutation passed on to daughter cells.
Preventing overuse of antibiotics
Good hygeine in hospitals to prevent spread of antibiotic resistant strains
MRSA
- carried in skin or nose
- causes boils or fatal blood poisoning
- resistant to methicillin
C Difficile
- Bacteria in guts
- Produce toxins that damage small intestine lining, lead to bleeding and diarrhoea
- Antibiotics damage healthy gut bacteria, reducing competition for antibiotic resistant gut bacteria
To identify bacteria, look at:
- Shape
- Staining cell wall (gram positive, gram negative bacteria)
Structure and how each infects:
Bacteria
Virus
Fungi
Bacteria
- releases toxins
- flagella, pili, slime capsule, cell wall, cell membrane, cytoplasm, ribosomes, plasmid, nucleoid
Virus
- Can only reproduce in host cell
- Passes through cell membrane of host cell
- Copies itself using host cell’s enzymes
- leaves cell and causes lysis
- genetic material
- capsids
- attachement proteins
Fungi
- release enzymes which breaks down material
- saprotrophs (absorb)
- release spores when reproducing
