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level: Microorganisms and Immunity 1

Questions and Answers List

level questions: Microorganisms and Immunity 1

QuestionAnswer
what are lysosomes?vesicles containing enzymes they can fuse with phagocytes to form a phagolysosome they are made by the Golgi apparatus
what are interferons?proteins involved in cell communication to prevent infection they are specific to viruses
how do interferons prevent infection?prevent viral replication they activate specific immune response cells promote inflammation
define specific immune responsethe body's response to the presence of foreign antigens causing antibodies to form
what is an antigen?proteins or polysaccharides found on the surface of a cell must be identified as foreign cause the formation of antibodies
structure of an antibodythey are attached to B-cells made up of 4 polypeptide chains disulphide bridges hold them together they have active sites specific to the antigen the constant region allows binding to receptors the variable region is complementary to the antigen
function of an antibodyagglutination neutralises toxins block cell surface receptors stimulate the production of histamines
describe the process of antigen presentation by phagocytesphagocytosis of the pathogen has occurred the phagocyte sticks the antigen on its surface by its MHC this activates the specific immune response cells
what is the role of a neutrophil in the immune system?they are part of the primary immune defence system they block, disable, digest and ward off invading pathogens
what is the role of a monocyte in the immune system?immature macrophages they engulf and digest pathogens
what is the role of T-cells in the immune system?T-helper cells support B-cells in the production of antibodies T-killer cells attack cells that have been infected T-memory cells remember the specific antigen
structure of virusesstrands of RNA or DNA attachment proteins (gp120) capsid protein-lipid membrane or viral envelope reverse transcriptase, intergrase, protease
cell mediaTed responsethe host cell becomes an APC by displaying antigens on its MHC T killer binds to the APC with CD4+ receptors cytokines secreted by T helper stimulate T killer to divide by mitosis T killer divides forming active T killer and T memory cells active T killer cells bind to the APC and secretes chemicals which causes pores to form in the cell membrane and the cell bursts and dies
post trancriptional modifications of mRNARNA splicing a gene is transcribed resulting in pre-mRNA all introns and some exons are removed the remaining genes are joined back up by spliceososomes the same exons can be joined in many ways to produce different versions of mature functional RNA
the major routes for pathogens into the bodyinhaled ingested cuts in the skin
physical barriers to infectionskin and gut flora the skin stomach acid lysozymes in tears
how does the skin prevent infection?skin is made of the hard substance keratin hard to diffuse into or penetrate
how does stomach acid help prevent infection?hydrochloric acid the conditions are too acidic for bacteria to survive
how do skin and gut flora help prevent infection?natural bacteria found on the surface of the skin and gut out-competes other pathogens for space, food and moisture
what are lysozymes?enzymes that are found in lysosomes examples include carbohydrase, protease and lipase they are commonly found in mucus, tears and other fluids they break down the bacterial cell walls by attacking the peptidoglycan through hydrolysis
outline the process of phagocytosisphagocyte attaches to the microbe it is engulfed into a vacuole called a phagosome phagocyte and lysosome fuse to form a phagolysosome the microbe is killed and digested by lysozymes released by the lysosome
describe the series of events involved in the non-specific responsedamaged cells send out chemicals causing neutrophils to accumulate at the site in the capillary mast cells in the tissue fluid are at the site mast cell release histamines histamines cause vasodilation of local arterioles causing local redness and heat they also make the capillary walls leaky because the endothelial cells part slightly this allows plasma, antibodies and neutrophils to enter and destroy the bacteria this will increase tissue fluid in the capillary causing oedema (swelling)
how does inflammation occur?histamines cause vasodilation of local arterioles this causes local redness and heat histamines also separate the endothelial cells this allows more tissue fluid to enter the arterioles causing oedma
why are theses series of events termed non-specific?because the system does not involve the production of antibodies complementary to the antigen on the microbe
what is the role of B-cells in the immune system?B-effector: forms plasma cells B-memory: they can record the specific antibodies needed should a second infection reappear
how does TB cause infection?caused by mycobacterium tuberculosis the bacteria is inhaled from the air of an infected person and lodges in the lungs TB is usually latent until the immune system is weak active TB will slowly destroy the lung tissue leading to breathing problems, coughing, weight loss and fever TB bacterium can spread through the body in the tissue fluid or lymphatic system
T helper activationthe bacteria is engulfed by a macrophage the macrophage displays antigens on its MHC the macrophage acts as an APC T helper cell binds to the macrophage APC by CD4 receptor this activates the T-helper cell to divide by mitosis to form T memory cells and active T helper cells
process of the humoral responseT-helper cell activation has occurred B-cells engulf the pathogen, digest it and present its antigen on its surface by the immunoglobulin/antibody it becomes an APC active T-helper cells bind to the APC releasing cytokines cytokines cause them to divide into B-effector and B-memory cells
what is the MHC?major histocompatability complexes a group of genes that code for proteins found on the surface of cells help the immune system recognise foreign substances
B effector stagehumoral response the B effector cells differentiate into plasma cells plasma cells synthesise antibodies
how do antibodies destroy pathogens?agglutination neutralising toxins block receptors stimulate the production of histatmines lysis precipitation
what is HIV?human immunodeficiency virus destroys T-helper cells leading to AIDS flu-like symptoms like fever, tiredness and headaches a person is HIV positive when HIV antibodies are present in the blood
differences between bacteria and virusesbacteria has no capsid viruses have no pili, flagellum, cytoplasm, peptidoglycan cell wall, mesosome, ribosomes, plasmid, nucleoid bacteria are bigger viruses need a host cell to replicate bacteria are prokaryotes bacteria only have DNA whilst viruses can have both RNA and DNA
what is an APC?antigen presenting cell displays foreign antigens by the MHC on their surfaces for T cells to recognise
similarities between bacteria and virusesboth cause infection both are not eukaryotes both have enzymes
structure of bacteriamesosomes ribosomes nucleoid cell wall circular DNA plasmid flagella pili cytoplasm
how can the non specific response be triggered?the presence of antigens and their chemicals released from a foreign cell
T-cellsT-lymphocyte three types: T-helper cells (naïve/active), T-memory cells, T-killer cells have CD4 receptors on their surface they mature in the thymus gland
what are Lymphoctes?T-cells and B-cells type of white blood cell found in the lymph B-cells produce antibodies T-cells provide immunity and also destroy foreign cells
what is the role of platelets in the immune system?healing first responder when a foreign particle enters the bloodstream
why does agglutination destroy pathogens?brings microbes closer together so phagocytosis is easier
B-cellsB-lymphocytes they are covered in immunoglobulins/antibodies two types: B-effector and B memory they mature in the bone marrow
why does stimulating the production of histamines help destroy pathogens?allows an inflammatory response to occur
what are the stages of the humoral response?T helper activation B effector stage
how does precipitation help antibodies destroy pathogens?soluble toxins are made insoluble
foreign cellsmicrobes, pathogens, viruses, bacteria cells/particles that are not recognised as our own
give the names of blood cells involved in the non-specific immune responseneutrophils, mast cells, monocytes/macrophages,