Unit 4 - Communicable disease, disease prevention and the immune system Flashcards
Pathogen
Microorganism that causes disease
Lives in hosts
Communicable diseases
Any disease transmitted from one person or animal; contagious
4 groups of microorganisms
Bacteria
Fungi
Viruses
Protoctista
Diseases caused by bacteria
Tuberculosis
Bacterial meningitis
Ring rot in plants
Diseases caused by viruses
HIV/ AIDS
Influenza
Tobacco mosaic virus
Diseases caused by fungi
Black sigatoka
Ringworm
Athletes foot
Diseases caused by protoctista
Malaria
Potato/ tomato blight
Prokaryotic pathogens
Bacteria
Eukaryotic pathogens
Fungi
How do bacteria damage hosts
Multiply rapidly
Damage cells by releasing waste products and/or toxins
How do fungi damage hosts
Hyphae release extracellular enzymes e.g. celluloses to digest plant tissue
Causes decay and leaf death —> no photosynthesis
May produce toxins
Are viruses eukaryotic or prokaryotic
Neither; they’re dead
How do viruses damage hosts
Invade living cells where genetic material in virus takes over the biochemistry of the host cells
Makes more copies
Host cell bursts, releasing viruses
Bacteriophages
Viruses that can attack bacteria
How do protoctista damage hosts
Enter host cells and feed on contents before breaking over cells
How may protoctista enter through the body directly
Polluted water
Transmission
Passing a pathogen from an infected individual to an uninflected individual
Direct transmission
Passing a pathogen from host to new host, with no intermediary
Types of direct transmission
Physical contact
Faecal - oral transmission
Droplet infection
Transmission by spores
Physical contact
Touching an infected person
Touching contaminated surfaces
Exchanging bodily fluids
Faecal - oral transmission
Eating food or drinking water contaminated by pathogen
Droplet infection
Pathogens are carried in tiny water droplets in the air
Transmission by spores
Spores are the resistant stage of some pathogens
Can be carried in the air or reside on surfaces or in the soil
Indirect transmission
Pathogens are transmitted indirectly via a vector
Vector
Another organism that may be used by the pathogen to gain entry to the primary host
Cause of malaria
Plasmodium parasite
It enters the human host via a bite from a female Anopheles mosquito
Social factors affect direct transmission
Overcrowding Poor ventilation Poor sanitation Poor health - likely to contract other diseases Poor diet (malnutrition) Lack of education
Why is there a greater variety of diseases to be found in warmer climates
Many protoctists, bacteria and fungi can grow and reproduce more rapidly in warm and moist conditions
Why are plants targets for microorganisms
Manufacture sugars in photosynthesis and convert this into wide variety of compounds such as proteins and oils - rich source of nutrients for microorganisms
Passive defences
Prevent entry
Active defences
Induced when pathogen is detected
Plant passive defences
Cell wall Waxy cuticle Bark Stomatal closure Chemicals with anti pathogenic properties
Plant active defences
Production of callose Strengthen cell walls with additional cellulose and lignin Tylose formation Wide range of chemicals produced Necrosis
Callose as an active defence
Blocks plasmodesmata and sieve plates in the phloem, sealing off the infected part
Tylose
Ballon like swelling that fills the xylem vessel. When a tylose is fully formed it blocks the vessel
Necrosis as an active defence
Deliberate cell suicide
By killing cells surrounding the infections, pathogens access to water and nutrients is limited
Chemicals produced as a part of plants active defences
Terpenoids Phenols Alkaloids Defensins Hydrolysis enzymes
Terpenoids
Essential oils with anti-fungal and antibacterial properties
Phenols
Have antibiotic and anti-fungal properties
Tannins bind to salivary proteins and digestive enzymes, deactivating them
Alkaloids
Nitrogen-containing compounds that have a bitter taste to inhibit herbivores feeding
Inhibit protein synthesis
Also inhibit or activate enzyme action
Defensins
Small cysteine-rich proteins with anti-microbial properties
Act upon molecules in plasma membrane of pathogens
Hydrolytic enzymes
Found in spaces between cells
Include chitinases, glucanases and lysozymes
Glucanases
Hydrolyse glycosidic bonds in glucans
Primary Defences
Defences that prevent pathogens from entering the body
Non-specific defences
Prevent the entry of all pathogens
Primary non-specific responses
Blood clotting; vessels/skin receptor Expulsive reflexes Stomach acid Tears (enzymes break down e.g. bacterial cell wall) Wax in ears Mucous membranes Skin Inflammatory response
Main primary response
Skin
Cells in epidermis
Keratinocytes
How are keratinocytes produced
Cells produced at base by mitosis
Cells migrate to the top and keratinisation takes place
Keratinisation
Cytoplasm dries out and is replaced by keratin
Keratinised layer forms an effective barrier to pathogens
Where are mucous membranes found
In many of the body tracts that are at risk of infection as they are in contact with the external environment
What happens when mucus wafts to the top of the trachea
It enters the oesophagus and is swallowed. Most pathogens are killed by the acidity of the stomach
Examples of expulsive reflexes
Coughing
Sneezing
Vomiting
What are expulsive reflexes a result of
Irritation by micro-organisms or toxins in areas that are sensitive. The aim is to expel the microorganism
What happens when platelets come into contact with collagen in the skin or walls of damaged blood vessels
They adhere and begin secreting several substances including clotting factors and serotonin
Clotting factors
Thromboplastin
What does thromboplastin trigger
An enzyme cascade of reactions resulting in the formation of a blood clot. The final step is soluble fibrinogen being converted into insoluble fibrin fibres which forms a barrier
What does serotonin do
Makes the smooth muscle in the walls of the blood vessels contract, reducing supply of blood to the area
Inflammatory response
This is a localised response to pathogens resulting in inflammation at the site of a wound
Causes pain, heat, redness and tissue swelling
When mast cells are activated in damaged tissues, what chemicals are released from the cell
Histamines
Cytokines
Histamines
Makes arterioles dilate to increase blood flow (cause redness) and makes the capillary walls more leaky so more plasma is forced out. The extra tissue fluid causes oedema and pain
Oedema
Swelling
What do macrophages measure
Amount of bacteria entering the body
Roles of macrophages
Swallow pathogens and trap them in membranes
Breaks down pathogens by enzymes and kills them
Cause inflammation by ordering blood vessels to release water
Release interleukins