Communicable Diseases Flashcards
What is a pathogen?
A microorganism that causes disease.
Give a brief description how bacteria cause disease
Their presence can cause disease by damaging cells or by releasing waste products or toxins. These toxins break down cell membranes or inactivate enzymes or prevent cell divison. In plants they often live in the vascular tissues and cause blackening and death of tissues. Eg. ring rot
Explain a fungal infection in relation to animals
Fungus lives in the skin where its hyphae (forms a mycelium) grows under the skin. It sends out reproductive hyphae which grow to surface of the skin to release spores. Redness and irriation.
Explain a fungal infection in relation to a plant
- Fungus lives in the vascular tissue (gains nutrients).
- The hypae release extracellular enzymes (cellulases) to digest the surrounding tissue causes decay.
- Leaves become mottled in colour, curl up and shrivel before dying.
- Fruit and storage organs turn black and decay.
Explain how viruses infect cells
Viruses invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell to manufacture more copies of the virus (by inserting a section of their RNA into the DNA). The host eventually bursts releasing many new viruses which will infect healthy cells.
Explain how protoctista causes disease with example
Protoctista enter the host cell and feeding on the contents as they grow. Malrial parasite is called Plasmodium (immature forms that feed on haemoglobin)
Discuss the differences between bacteria, fungi, viruses and protoctista
Domain - prokaryote - eukaryote - no domain - eukaryote Kingdom - their names Autotrophic/heterotrophic - some are auto - hetero - none - some are auto Plasmids - yes - yes - no Nucleus - no - yes - no - yes
Name some bacterial diseases with their characteristics
TB
-kills cells and tissues in many parts but lungs are most affected
Bacterial Meningitis
-infection of the meninges (membrane around brain and spinal cord) membranes become swollen and causes damge to brain and nerves
Ring Rot
-ring of decay in the vasular tissue of a potato tuber or tomato + leaf wilting
Name some viral diseases with their characteristics
HIV/AIDS
- attacks cells in the immune system and compromises it
Influenza
- attacks respiratory system and causes muscle pain and headaches
Tobacco mosaic virus
- causes mottling and discolouration of leaves
Name some fungal diseases with their characteristics
Black sigatoka
- causes leaf spots on banana plants reducing yield
Ring worm
- growth of fungus in skin with spore cases erupting through skin to cause rash (cattle)
Athlete’s foot
- growth under skin of feet (toes)
Name some protoctistan diseases with their characteristics
Blight
- affects both leaves and potato tubers (tomatoes and potatoes)
Malaria
- parasite in the blood that causes headache and fever and may progress to coma and death
What is the difference between passive and active defences?
Passive defences are present before infection; prevent the entry and spread of a pathogen. Active defences are specific chemicals in the cell walls that are produced when pathogens attack. They fortify defences already present.
Describe and name 4 physical plant defences
- Cellulose cell wall - acts as physical barrier and contains chemicals that can be activated when pathogen is detected
- Lignin thickening of the walls - waterproof and indigestable
- Waxy cuticles - prevent water collecting on the cell surfaces (pathogens need water to survive)
- Bark - has chemical defences
Describe and name 3 physical plant defences
- Stomatal closure - entry points, controlled by guard cells, when pathogen detected they’ll close
- Callose - deposited in the sieve tubes at end of growing season, blocks flow in the sieve tube, prevents pathogen spreading around plant
- Tylose - swelling that fills the xylem vessel, plugs the vessel so it can’t carry water, prevents spread of pathogens throughout heartwood, terpenes high conc are toxic to pathogens
Describe and name 6 active plant defences
- cell walls become thickened with additional glucose
- deposition of callose between plant cell wall and cell membrane near pathogen, impedes cellular penetration at site of infection (strengthens cell walls and blocks plasmodesmata
- oxidative bursts that produce highly reactive O2 damage the cells of organisms
- increase in production of chemicals
- Necrosis - deliberate cell suicide, plant can limit the pathogens access to water and nutrients (stops spread), intracellular enzymes activated by injury, destroy damaged cells and produce brown spots on leaves
- Canker - sunken necrotic leison in the woody tissue (main stem) causes death of cambium tissue in bark
Name and describe 3 chemicals used in active plant defence
- Terpenoids - anti bacterial, fungal oils (scent)
- Defensive proteins defensins - small cysteine rich proteins, anti microbial activity, inhibit the action of ion transport channels
- Hydrolytic enzymes - spaces between cells
Chitinases (break down fungi chitin)
Glucanases (hydrolyse glycocidic bond in glucans)
Lysozymes (degrading bacterial cell walls)
Name and describe 2 chemicals used in active plant defence
- Phenols - antibiotic/fungal, tannins in bark inhibit attack of insects - bind to salivary proteins and digest trypsin and chymotrypsin, these insects don’t grow
- Alkaloids - caffein, nicotine, cocaine, morphine, solanine. Bitter taste. Inhibit or activiating enzyme action. Inhibit protein synthesis. Less larger animals feeding means less damage allowing pathogens in.
Give examples of direct transmission - direct contact in animals
- kissing and bodily fluids bacterial meningitis, HIV - direct skin to skin contact ringworm - microoragnisms from faeces diarrhoeal disease
Give examples of direct transmission - inoculation in animals
- break the skin HIV/AIDS - animal bite rabies - puncture wounds or sharing needles septicaemia
Give examples of direct transmission - ingestion in animals
- contaminated food or water
amoebic dysentry
