Non Specific Plant And Animal Defence Flashcards
state and explain 4 physical plant defences against pathogens
- waxy cuticle = physical barrier against pathogen entry + stops water collecting on the leaf reducing infection between plants in water
- cell walls = physical barrier against pathogens that make it past waxy cuticle
- produce polysaccharide - callose = deposited between cell walls and plasma membranes, making it harder for pathogens to enter cells, is deposited at the plasmodesmata so limits spread of viruses between cells
- lignin = waterproof substance which thickens cell walls
state and explain 4 chemical plant defences against pathogens
- produce antimicrobial chemicals = kill pathogens or inhibit their growth
- produce chemicals that are toxic to insects = e.g. cyanide, reduces amount of insect- feeding on plants
- phytoalexins are produced in response to contact with a pathogen or parasite = fungicidal, specific to particular attacking organisms, inhibiting their growth
- insecticides = often alkaloid substances that are toxic to insects
what are non-specific defence mechanisms for animals against pathogens?
mechanisms against any pathogen, so doesn’t need to recognise its antigen shape
what is the purpose of the first line of defence for the non specific responses?
to prevent pathogens from entering the body
what is the purpose of the second line of defence for the non specific responses?
to deal with pathogens which have accessed the blood supply and tissues - to stop them from reproducing or entering cells
what is the purpose of the third line of defence for the specific responses?
to recognise pathogens and make antibodies against them so that the pathogen will be destroyed. also so that future exposure to the same pathogen will be dealt with quickly and illness prevented
explain the skin as a non specific defence in animals
- forms a continuous, physical barrier which prevents pathofens from reaching the tissues
- outer layer of cells are not alive = prevents being used as host cells
- outer layer constantly being sloughed off and replaced = difficult for pathogens to establish a reproducing colony
- production of sebum = has antimicrobial properties
- commensals = live on our skin and occupy the ecological nivhe that the skin may provide
explain mucus membranes as a non specific defence in animals
- found in areas not covered by skin e.g. lining of airways and digestive track
- mucus makes it more difficult for the pathogens to make contact with the cells underneath it
explain blood clotting as a non specific defence in animals
- when there is a breech in the skin caused by trauma it is important that the wound is sealed as quickly as possible
- the prevents excessive blood loss and opportunistic pathogens from gaining access to the tissues underneath the skin
explain the process of the clotting cascade
- blood clot is formed from many strands of the insoluble protein fibrin, which acts as a mesh to catch red blood cells forming a temporary seal to plug the wound
- the inactive, soluble precursor of fibrin is fibrinogen, which circulates in the blood instead of fibrin which would form blood clots at any time
- it converts to fibrin in the presence of the enzyme thrombin has to be made from its inactivated enzyme precursor, prothrombin in the presence of thromboplastin and Ca+
- thromboplastin is released by platelets when they are activated, denting damage has been done to the blood vessel wall
- once wound has been sealed, epidermis cells undeergo mitosis to permanently cover the wound. as the skin heals the blood clot dries out to form a scab, and ocne skin has healed underneath, the scab will fall off
explain expulsion reflexes as a non specific defence in animals
- various physiological processes which can expel pathogens from the body
- include coughin, sneezing, vomiting and diarrhoea
- if pathogens are removed from the breathing or digestive systems, then it will not be able to access the blood system and travel to other parts of the body
explain inflammation as a non specific defence in animals
redness
heat
swelling
pain
explain how fever response is created in the body
when a pathogen invades the body, cytokines stimulate the hypothalamus to reset the thermostat and the body temperature goes up from 37 degrees to 38/39 degrees.
why is the fever response a useful adaptation for us?
- higher temperatures inhibit pathogen reproduction
- the specific immune system works faster at higher temperatures as more kinetic energy = cells with specific receptors will encounter a foreign antigen
what is a phagocyte?
a type of white blood cell that carries out phagocytosis (engulfment of pathogens). they’re found in the blood and in tissues and carry out a non specific immune reponse
