Download Plant Defence Mechanisms (Cellular)

Chapter 11
Cellular Defence Mechanisms
Cellular Defence Mechanisms in Humans
Different types of white blood cells exist which defend the human body against
pathogens in 2 different ways. (Pathogen = disease causing micro-organism)


Phagocytosis
Antibody formation
Use Fig 11.1 p 70 Torrance New Higher Biology to draw and label the different types
of white blood cells.
Phagocytes are cells capable of phagocytosis
Phagocytosis
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Chapter 11
Immune Response
Immunity is an organism’s ability to resist infectious disease.
Why is phagocytosis seen as an example of a non-specific immune response?
Antibody production is a specific immune response because appropriate
complementary antibodies are produced by a particular type of lymphocyte in
response to one specific antigen.
Write clear notes on the following:



Antigen
Antibody
The action of antibodies
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Immunological memory
Primary and secondary responses
Primary response
Secondary response
Explain why subsequent exposure to the same antigen at a later date often does not
result in disease.
Diagram
Explain the role of memory
cells in the secondary
response
.
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Chapter 11
Types of specific immunity
Active
Passive
( person produces their own antibodies)
Naturally
acquired
(antibodies are supplied ready made)
Artificially
acquired
Natural
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Artificial
Chapter 11
Plant Defence Mechanisms (Cellular)
(1)
By Isolating The Site of Infection
i)
Gall: a swelling that isolates a parasite e.g. oak apple.
ii)
Callus Formation: if a plant is damaged, the wound becomes
plugged by a mass of undifferentiated cells.
iii) Lignin: increased lignification in the plant cell wall acts as a
Barrier which is resistant to fungal attack.
iv) Callose: sieve tubes are blocked off by heavy Callose deposits (a
form of glucose), therefore preventing invading microbes from spreading
through the plant via phloem tissue.
v)
Ethylene: a gass that causes leaf fall. Increased ethylene
production is found to occur in the leaves of various plants following viral
infection.
vi) Resin: in response to injury, many trees and shrubs produce
resin which seals the wound. It is also distasteful to animals.
(2)
By Producing Toxic Compounds
i)
Hydrogen Peroxide:
Pathogen
Pathogen
Invades
Oxidised
H2 02
H20o Produced
Enzyme
Peroxidase
H2 + 02
ii)
Phytoalexins: fungal infection can lead to the production of large
amounts of phytoalexins which are Antifungal chemicals, therefore stop
the spread of the fungus.
Tanins: it is an acidic chemical which can be effective against the
protein coats of a virus e.g. produced by potatoes and apples.
iii)
iv)
Cyanide: e.g. produced by white clover. Cyanide is a poison and
when leaves are damaged by grazing, hydrogen cyanide is produced.
Enzyme
Glycoside _____________________ Hydrogen Cyanide
(non toxic)
(toxic)
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Chapter 11
v)
Nicotine: a poison produced by tobacco plants.
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