Microorganisms and disease Flashcards
Difference between bacterial cell and human cell
- 70s (smaller) ribosome, 80s (larger) ribosome
- no membrane bound organelles, membrane bound organelles
- no nucleus, nucleus present
- circular DNA, linear DNA
How phagocytosis destroys bacteria
- macrophage engulfs bacteria (endocytosis)
- vesicle containing pathogen fuses with a lysosome
- enzymes digest bacteria
- antigens are separated off (antigen processing)
- antigen combines with MHC complexes which move to outer cell membrane
- macrophage becomes APC, activating cells in specific immune response
The role of T helper cells in the immune response
- macrophage becomes an APC
- T helper cell with complementary CD4 receptor binds to the antigen/MHC complex on the APC
- T helper cell is activated and divides to form active T helper cells and T memory cells.
- each T cell has same CD4 receptor, so are specific to original antigen
- T cells stimulate immune response
- T helper cell binds to B cell APC and produces cytokines that stimulate the B cell to divide and produce antibodies
- stimulates specific immune response
Describe how counting the numbers of T helper cells can provide a measure of AIDS in a person with HIV
- HIV infects T helper cells
- T killer cells then kill T helper cells
- as HIV progresses, T cell count will drop
Give two common symptoms of HIV and AIDS
- karposi’s sarcoma
- excessive sweating
- chronic lung infections (TB)
- pneumonia
- opportunistic infection
- weight loss
- extreme tiredness
Bacteria structure that contains resistance genes that can be transferred to another bacteria
-plasmid
Bacteria structure where protein synthesis takes place
- ribosome
Bacteria structure that contains enzymes for respiration
- mesosome
How TB is caused
- by droplet infection, inhalation of bacteria by droplet or dust
- mycobacterium tuberculosis
- formation of tubercles in the lungs
How TB avoid being destroyed by the immune system
- present inside macrophages
Describe the role of B cells and T cells in preventing the development of the symptoms of TB in an infected person
- antigen binds to B cell, B cell become APC
- T helper cell binds to APC
- T helper cell releases cytokines which stimulate B cell proliferation
- B cell divide into B effector cells and B memory cells
- B effector cells differentiate in plasma cells which secrete antibodies
Why a patient infected with TB is more likely to develop symptoms of the disease if they are also infected by HIV
- HIV infects T helper cells, which are destroyed by T killer cells
- T helper cells are required to stimulate proliferation of B cells to produce antibodies
- bacterial cells not destroyed by the immune system
- bacteria proliferate
Symptoms of TB
- tubercles
- fever
- excessive coughing/coughing of blood
- weight loss
Explain why the response of the immune system to the viral proteins is an example of active immunity
- it is the response of immune system to antigen
- producing antibodies
- T killer cell
Explain how active immunity provides immunity against future infections by the virus
- memory cells are produced
- response more rapid to second infection, faster antibody production
- prevents symptoms
- high concentrations of antibody produced
- antibodies produced for longer
- secondary response
What determines the usefulness of a vaccine
- how quickly the population can be protected, time to produce enough doses for effective protection of population
- if it is possible to keep high levels of herd immunity
- if distribution is more reliable, possible to remote areas
- if it has to be refrigerated/special treatment during distribution
- how fast they can develop a vaccine against a new strain of virus, rapid response to change in pathogens
Suggest how the use of viral DNA might be more effective than viral protein in producing herd immunity to a virus
- antibodies only destroy virus in blood
- virus infects body cells
- viral DNA method stimulates T killer cells
- T killer cells destroy virally infected cells
- virus cannot spread/hide inside cells
- T memory cells produced
- more lymphocytes to combat infection
State how the genetic material in HIV differs from the genetic material to the Mycobacterium tuberculosis
- RNA in HIV and DNA in bacterium
- nucleic acid is circular in bacterium and linear in HIV
- bacterium contains plasmids, no plasmids in HIV
Explain the change in the numbers of CD4 T-lymphocytes during the first 6 weeks after infection with HIV
- glycoprotein 120 on virus binds with CD4 receptors
- on surface membrane of lymphocytes
- viral RNA enters T cell/lymphocyte
- viral RNA used to produce viral DNA in T cell
- by action of reverse transcriptase
- formation of new viruses
- lymphocyte destroyed when new viruses bud out cell (and take cell membrane)
- T killer cells destroy T helper cells
Explain why unbroken skin is an effective barrier against HIV infection
- keratin in skin surface/epidermis
- forms a hard impenetrable physical barrier
Effect of fall in T count on one other component of the infected person’s blood
- B cells not activates
- so fewer antibodies produced
- T killer cells increases
Describe how viruses are recognised and destroyed by the immune system
- activation of T cell, virus engulfed by macrophage
- antigens presented on macrophage, APC
- T helper cell with complementary CD4 receptor binds to antigen/MHC complex
- to form clones of active T helper cell and T memory cells
- leads to cell mediated/humeral response
- cell mediated, T killer cell with complementary receptor binds to anitigen/MHC complex on APC
- T helper cell releases cytokines that stimulate division
- T killer cell releases chemicals that cause lysis of virus infected cells
- humoral response/clonal selections, antigen binds to B cell
- B cell becomes APC
- T helper cell binds to MHC/antigen complex and stimulate division
- B effector cells differentiate into plasma cells
- plasma cells secrete antigen specific antibodies
- antibodies label antigens for phagocytosis
