Disease - 4 Flashcards
How does the waxy cuticle act as a plant defence
physical barrier and no water collection on wax
How does the cell wall act as a plant defence
barrier and contains chemicals
How does callose act as a plant defence
Prevents pathogens entering cells
Can also block phloem sieve plates,
preventing spread of pathogen
What is callose
Polysaccharide deposited between
cell walls and membranes when a
plant is infected
What are chemical plant defences
Antimicrobial chemicals which kill or inhibit the growth of pathogens - saponins
Chemicals toxic to vectors
What are primary defences
Prevent the entry of a pathogen into an organism
What are non-specific defences
Defences that will act on any type of pathogen
Examples of primary non-specific defences in animals
Skin
Blood clotting
Inflammation
Expulsive reflexes
Mucous membranes
Wound repair
What are the 2 types of white blood cells
Lymphocytes
Phagocytes
What are the 2 types of phagocytes
Macrophages
Neutrophils
Features of neutrophils
Multi-lobed nucleus
Short lived and released in large numbers
Undertake phagocytosis
Features of macrophages
Made in bone marrow
Travel through blood
Undertake phagocytosis
Display antigens
Describe the process in phagocytosis
The phagocyte recognises the antigens on the surface of the pathogen
Phagocyte engulfs the pathogen by folding its membrane inwards
This forms a phagosome
Lysosomes then fuse with the phagosome (phagolysosome)
Lysosomes release enzymes (lysins) to digest the pathogen
Harmless products absorbed
What are opsonin’s
Proteins in the blood that attach to the surface of pathogens to aid
phagocytosis
They serve as a marker and ‘tag’ pathogens
Phagocytes have receptors for opsonins and bind to them, the phagocyte
then engulfs the pathogen
what are cytokines
Cytokines
Proteins in the blood that attract phagocytes via cell signalling
Phagocytes that have engulfed a pathogen produce cytokines
When other phagocytes pick up the cytokine signal it informs them the
organism is under attack and phagocytes move to the site of infection
Features of the specific immune response
attack a specific pathogen
Much slower at first
Faster on second infections
More effective
What are antigens
Usually proteins or glycoproteins
Have a specific shape
Foreign antigens trigger immune response
What are antibodies
Y shaped proteins produced by B plasma cells
Have a complimentary shape
What are the 2 types of lymphocytes
T cells
B cells
Describe the structure of an antibody
Two heavy polypeptide chains
Two light polypeptide chains
Variable region
Antigen binding sites
constant region
Hinge region
How are the polypeptide chains held together
By disulphide bridges
What is the function of the variable region
Varies between antibodies
specific to an antigen
What is the function of the antigen binding site
complementary shape
to a specific antigen
two of these
What is the function of the constant region
Allows phagocytes to attach to antibody for phagocytosis
Same in all antibodies