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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 1 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 2 Chapter 11 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 . 3 Chapter 11 Types of specific immunity Active Passive ( person produces their own antibodies) Naturally acquired (antibodies are supplied ready made) Artificially acquired Natural 4 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) 5 Chapter 11 v) Nicotine: a poison produced by tobacco plants. 6