How does skin and mucous membranes protect the body from pathogens?
mucous membranes:
- are a thinner and softer type of skin w/sticky mucous
- sticky solution of glycoproteins trap pathogens
Skin:
- continuous
- many thick layers
- dry
- pH is slightly acidic, unfavourable for things to grow
Cells in the bloodstream
- platelets
- red blood cell
- lymphocyte
- phagocyte
Blood clotting
- platelet/cell damage release clotting factors
- this results in a cascade of rxns
- thrombin converts fibrinogen (soluble) into fibrin (fibrous and insoluble) (forms a mesh around wound site and captures blood cells and platelets to form a clot)
- fibron captures erythrocytes
- results in a clot (blood clotting must be monitored
- with presence of air, a scab forms, shields healing tissues underneath
Coronary heart disease
- Blood clots sometimes form in coronary arteries (called coronary thrombosis)
- coronary arteries become clogged (called atherosclerosis: occlusion on coronary artery)
- thus, heart tissues are not provided with a supply of O2
- may cause myocardial infarction (heart attack)
Risk factors for coronary heart disease
Genetic: high BP
Age: older people have a greater risk/less elasticity in arteries
Sex: males greater at risk
Exercise: lack of exercise increases risk: weakened circulation
Stress: linked to increased cortisol hormones in blood: increase atherosclerosis
First line of defence for pathogens
Phagocytic leukocytes (phagocyte)
Process of pathogen ingestion
- Pathogen approaches WBC
(Phagocytes can squeeze through pores of capillaries, chemotaxis (movement in response to chemicals) attracts phagocytes to area of invasion) - Antigens recognize pathogen and phagocyte attaches to cell surface of pathogen
- Phagocyte engulfs pathogen by endocytosis
- Lysosomes approach and attach to the pathogen: phagosome is formed (vesicle containing pathogen) lysosomes deposit enzymes into the phagosome
- Enzymes break down pathogen
- Waste products released by exocytosis
Antigen definition
Molecule found on a cell/virus surface that causes antibody formation
Antibody definition
Globular protein that recognizes a specific antigen and binds to it as a part of an immune response
What triggers an immune response?
- by “non-self” cells
Clonal selection (mainly involves lymphocytes)
- many lymphocytes: each type recognizes one specific antigen
- when immune system challenged by the invasion of a pathogen, corresponding lymphocyte responds
- lymphocyte clones itself, each of which produce antibodies to the pathogen
- process is called clonal selection (selection- lymphocyte is selected, clonal- lymphocyte is cloned)
What are the roles of antibodies????
- make a pathogen more recognizable to phagocytes (more easily engulfed)
- prevent viruses from docking into host cells as they cannot enter the cells
Lifespan of antibodies
- persist only for a few weeks or a few months
- cloned cells remain as memory cells, ready for a second invasion by the pathogen (called immunity!)
Antibiotics use
Used in the prevention/treatment of prokaryotic bacteria
How do antibiotics interfere with prokaryotes?
- destroy cell walls and membranes
- interfere w/ protein synthesis
- interfere w/ DNA/RNA synthesis
- other metabolic processes (such as enzyme function)
What types of cells can antibiotics affect?
- not eukaryotic cells
- (yes) prokaryotic cells
- note: viruses are non-living therefore antibiotics cannot be used on viruses
Antibiotics discovered in which organism?
Saprotrophic fungi
Know Penicillin
Nothing here
Viruses characteristics
- non living (can only reproduce in a host cell)
- use host cell metabolism, therefore not effected by antibiotics
- protected by the host cell structure
- structure very different from prokaryote (protein capsid and genetic material: no cell wall or membrane)
What can be used on viruses?? (NOT ANTIBIOTICS!!!!)
- Antivirals. (On some, targeting virus enzymes)
Antibiotic resistance (how to avoid??)
- prescribe antibiotics only for serious bacteria infections (e.g. not for food poisoning
- patients complete courses of antibiotics to eliminate bacteria complete (kill off all bacteria)
- high standards of hygiene to eliminate cross contamination
- farmers not using antibiotics on animal feeds to stimulate growth
- pharmaceutical companies developing new types of antibiotics (no new antibiotics since 1980s)
HIV (what is it?)
- HIV gradually attacks the immune system
- harder to fight off other infections and diseases
- no cure for HIV
AIDS
- Syndrome caused by HIV
- immune system weak
- last stage of HIV: body cannot defend itself, can develop diseases and can cause death if left untreated
