Topic 5 - Preventing and Identifying Disease Flashcards

1
Q

Describe the physical defence system within plants

A

● Waterproof waxy cuticle - surface barrier preventing the entry of pathogens
● Cellulose cell wall - further barrier against pathogens

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2
Q

Give some examples of chemical barriers in plants

A

● Secretion of toxins to reduce damage by
pests e.g. stinging nettles
● Production of antibacterial chemicals that kill
bacterial pathogens

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3
Q

Why are chemicals produced by plants useful?

A

They produce physiological effects on the body so can be used in medicines to treat disease

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4
Q

Give an example of a medicine derived from plants

A

● Quinine - antimalarial, bark of Cinchona sp.

● Aspirin - painkiller, bark/leaves of Salix alba

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5
Q

Why are plant defence systems important?

A

● 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

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6
Q

How can plant diseases be detected and identified in the field?

A

● 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

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7
Q

Why is it difficult to identify a disease using symptoms alone?

A

Many diseases may have similar symptoms

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8
Q

How can plant diseases be detected and identified in the lab?

A

● 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

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9
Q

What is a non-specific defence?

A

● Always present
● Same for all organisms
● Prevents pathogens from entering the body

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10
Q

Give some examples of the body’s physical defence system

A

● 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

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11
Q

Give some examples of the body’s chemical defence system

A

● 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

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12
Q

What is the immune system?

A

● The body’s defence against pathogens
once they have entered the body
● Aims to prevent or minimise disease
caused by pathogens

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13
Q

How do white blood cells detect pathogens in the body?

A

Pathogens have unique antigens on their surface which are detected by specialised receptors on white blood cells

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14
Q

How does the immune system destroy

pathogens?

A

● 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.

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15
Q

What are memory lymphocytes?

A

● 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

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16
Q

Compare the primary and secondary immune responses

A

The secondary response produces antibodies more rapidly and in higher
concentrations than in the primary response. The pathogen is destroyed
before it can cause symptoms.

17
Q

What is a vaccination?

A

● Deliberate exposure of an individual to foreign antigens
● Triggers an immune response (produces antibodies) and provides immunity (due to memory cells)
● The individual does not contract the disease that they are being immunised against

18
Q

Describe the components of a vaccine

A

Dead, weakened or inactivated pathogens with their surface antigens
still present

19
Q

What are the benefits of vaccinations?

A

● Herd immunity - vaccination of a significant
proportion of the population gives some
protection to individuals who are not immune
● Helps to prevent epidemics and pandemics

20
Q

What are the drawbacks of vaccinations?

A

● High mutation rate of viruses changes the structure of viral antigens,
making vaccines that are already available ineffective
● Not guaranteed to work
● Inactivated pathogens may mutate and become pathogenic
● May cause an adverse reaction
● Vaccination programmes are costly