Topic 5 - Preventing and Identifying Disease Flashcards
Describe the physical defence system within plants
● Waterproof waxy cuticle - surface barrier preventing the entry of pathogens
● Cellulose cell wall - further barrier against pathogens
Give some examples of chemical barriers in plants
● Secretion of toxins to reduce damage by
pests e.g. stinging nettles
● Production of antibacterial chemicals that kill
bacterial pathogens
Why are chemicals produced by plants useful?
They produce physiological effects on the body so can be used in medicines to treat disease
Give an example of a medicine derived from plants
● Quinine - antimalarial, bark of Cinchona sp.
● Aspirin - painkiller, bark/leaves of Salix alba
Why are plant defence systems important?
● Plants are producers so all organisms higher
up in food chains rely upon their survival and ability to fight disease
● Important in maintaining human food security
How can plant diseases be detected and identified in the field?
● Observation of symptoms e.g. Chalara ash dieback disease causes bark lesions. Books and online resources aid identification
● Analysis of the distribution of infected plants can indicate the type of pathogen involved and its mode of transmission e.g. airborne
● Changing environmental conditions to eliminate other causes such as nutrient deficiencies or water-logged soils
Why is it difficult to identify a disease using symptoms alone?
Many diseases may have similar symptoms
How can plant diseases be detected and identified in the lab?
● Detection of foreign antigens in a sample of
plant tissue using monoclonal antibodies
● Analysis of DNA to identify any pathogen DNA
in a tissue sample
What is a non-specific defence?
● Always present
● Same for all organisms
● Prevents pathogens from entering the body
Give some examples of the body’s physical defence system
● Skin - protective surface barrier
● Blood clotting - platelets seal wounds preventing entry of pathogens into the blood
● Respiratory tract - mucus traps pathogens, cilia waft
mucus to the back of the throat where it is swallowed
Give some examples of the body’s chemical defence system
● Tears - contain lysozyme which digests bacterial
cell walls, killing bacteria and protecting the eye
● Hydrochloric acid in stomach - acidic pH kills
pathogens that are swallowed
What is the immune system?
● The body’s defence against pathogens
once they have entered the body
● Aims to prevent or minimise disease
caused by pathogens
How do white blood cells detect pathogens in the body?
Pathogens have unique antigens on their surface which are detected by specialised receptors on white blood cells
How does the immune system destroy
pathogens?
● B-lymphocytes (type of WBC) produce antibodies in
response to a particular antigen
● Each antibody is specific to an antigen and binds to it
● Antibodies ‘tag’ pathogens or clump them together,
disabling them so that they can be killed by other WBCs.
What are memory lymphocytes?
● WBCs produced in response to a foreign antigen that remain in the body after a pathogen has been destroyed
● Provide immunity - if the body is re-infected, antibodies are produced more rapidly and the pathogen is
destroyed before it can produce disease symptoms
