Communicable Diseases Flashcards
What is a pathogen?
An organism which causes disease
Passive Physical plant defences
Cellulose cell wall - physical barrier
Lignin cell wall - waterproof, almost indigestible
Bark - contains chemicals to defend against pathogens
Waxy cuticle - prevents water collecting on the cell surfaces, creates absence of water which pathogens need to survive
Closed stomata - when pathogen detected to prevent pathogens entering
Callose - deposited around sieve plates and blocks flow in sieve tube, preventing spread of pathogens
Tylose - plugs xylem vessel, preventing water flow and blocks pathogen, contains toxins to pathogens
Passive Plant chemical defences
Plant tissues - contain anti pathogenic properties e.g terpenoids, or phenols, alkaloids, hydrolytic enzymes
Terpenes in tyloses and tannins in bark are present before infection
Why are chemical defences made after the infection is detected in plants?
Production of chemicals requires lots of energy
Active physical plant defences
Cell wall - becomes thickened and strengthened with cellulose
Oxidative bursts - produce highly reactive oxygen molecules to damage pathogen cells
Callose - deposited between plant cell wall and cell membrane to prevent cell penetration
Necrosis - deliberate cell suicide
How does Mycobacterium tuberculosis cause disease?
Triggers response by infecting phagocytes in the lungs
Infected phagocytes are sealed in waxy coated tubercles so bacteria remains dormant
If another factor weakens immune system, bacteria becomes active and destroys lung tissue
How does HIV result in aids?
Attachment proteins bind to complementary CD4 receptors
HIV particles replicate inside cells killing or damaging them
AIDS develops when there are too few Th cells for immune system to function
Describe 3 fungal infections
Black Sigatoka
Ring worm
Athletes foot
How are communicable pathogens transmitted directly?
Inhalation
Skin to skin contact
Passively through wounds
Hoe are communicable pathogens transmitted indirectly?
Consumption of contaminated food
Via a vector
Spores
4 physical barriers to pathogens in plants
Cellulose cell walls
Lignified layer
Waxy upper cuticle
Old vascular tissue is blocked to prevent pathogens spreading inside plant
2 mechanical responses to pathogens in plants
Guard cells close stomata
Thick polysaccharide Callose depositors between cell wall and plasma membrane to limit spread
Describe chemical defences plants use against pathogens
Terpenoids (essential oils) e.g methols act as antibacterials
Phenols e.g tannin inhibit insects from attacking by interfering with digestion
Alkaloids e.g caffeine and morphins deter herbivores from feeding due to bitter taste
Defensins inhibit transport channels
Hydrolytic enzymes e.g chitinases which break down cell wall of invading organisms
5 barriers to infection in animals
Skin is a tough keritinised layer
Blood clotting prevents access through cuts
Hydrochloric acid in stomach kills bacteria
Harmless bacteria in gut which increases interspecific competition with pathogens
Mucous membranes to trap pathogens
Name 4 ways the non specific immune system responds to infection
Inflammation
Phagocytosis
Digestive action of lysosomes
Production of antiviral agents
