topic 11 Flashcards
every organism has —– ——– on the surface of their cells
unique molecules
antigens on the surface of red blood cells
stimulate antibody production in a person with a different blood group
describe the presence and absence of antigens on the surface of blood cells from different blood groups
- all three alleles involve a basic antigen sequence called antigen H
A: this is modified by the addition of molecule N-acetylgalactosamine
B: additional molecule is galactose
AB: both types of antigen
O: neither surface glycoprotein
what happens if a recipient is given a transfusion involving the wrong type of blood?
an immune response occurs. antibodies are produced, agglutination (clumping) occurs, followed by hemolysis where red blood cells are destroyed and blood may coagulate in vessels
describe an immune response
- macrophage ingests pathogen and displays antigens on it
- helper T cell specific to the antigen is activated by the macrophage
- B cell specific to the antigen is activated by proteins from the helper T cell
- B cell divides repeatedly to produce antibody-secreting plasma cells
- B cell also divides to produce memory cells
- antibodies produced by the clone of plasma cells are specific to antigens on the pathogen and help destroy it
how does activation of helper T cells work?
they have an antibody-like receptor protein in their plasma membranes, which can bind to antigens displayed by macrophages
how does the structure of plasma cells relate to their function?
- the cytoplasm contains an extensive network of rough endoplasmic reticulum (rER), which manufactures, modifies, and transports proteins (antibodies).
- The range of genes expressed is lower than a typical cell as the cell produces a lot of the same protein
define clonal selection
the generation of large numbers of plasma cells that produce one specific antibody type
give and explain 4 ways in which antibodies aid the destruction of pathogens
- opsonisation- make the pathogen more recognisable to phagocytes so they are more readily engulfed. also, once bound, they can link the pathogen to phagocytes
- neutralisation of viruses and bacteria: antibodies prevent viruses from docking to / entering host cells
- neutralisation of toxins- bind to the toxins produced by pathogens, preventing them from affecting susceptible cells
- activation of complement- antibodies activate a complement cascade which leads to the formation of a membrane attack complex that forms a pore in the membrane of the pathogen allowing water and ions to enter the cell and causing lysis
- agglutination of pathogens, preventing cell entry and aiding ingestion by pathogens
what is the complement system?
a collection of proteins which ultimately lead to the perforation of the membranes of pathogens
what does immunity depend upon?
the persistence of memory cells
describe how vaccines lead to immunity
they contain antigens that trigger immunity by causing a primary immune response but do not cause the disease
if the actual pathogen enters the body, it will be destroyed by the antibodies in a secondary immune response
what was the first infectious disease of humans to have been eradicated by vaccination?
smallpox
give 3 reasons why the smallpox eradication campaign was successful
- only humans can catch and transmit smallpox. there is no reservoir where the disease could be maintained and re-emerged
- symptoms of infection emerge quickly and are readily visible allowing teams to ‘ring vaccinate’ all of the people who might have come into contact with the afflicted person
- immunity is long-lasting
pathogens can either be
species-specific or able to cross species barriers
define a zoonosis
a pathogen which can cross a species barrier
these are a growing health concern
when and how are histamines released?
- by mast cells (immune cells found in connective tissue) secrete histamine in response to infection
- by basophils which circulate in the blood
state the effect of histamine on blood vessels
causes the dilation of the small blood vessels in the infected area causing the vessels to become leaky. This increases the flow of fluid containing immune components to the infected area and allows for some of the immune components to leave the blood vessel resulting in both specific and non-specific responses.
Sensitization: Initial exposure to allergen and
Allergic Reaction: Secondary exposure to same allergen
- when a specific B cell first encounters the allergen, it differentiates into plasma cells and makes large quantities of antibody (IgE)
- the IgE antibodies attach to mast cells, effectively ‘priming’ them towards the allergen
- upon re-exposure to the allergen, the IgE-primed mast cells release large amounts of histamine which causes inflammation
symptoms of an allergic reaction
nose: itching, fluid build-up, sneezing, mucus secretion and inflammation
allergic rashes and dangerous swelling (anaphylaxis)
define monoclonal antibodies
highly specific, purified antibodies that are produced by a clone of cells derived from a single cell. they recognise only one antigen
what is the use of monoclonal antibodies?
the treatment and diagnosis of diseases; eg the test for malaria or the creation of antibodies for injection into rabies victims
define a hybridoma cell
the cells formed by fusion of antibody-producing plasma B cells and myeloma (tumour) cells, which produce monoclonal antibodies
describe how hybridoma cells are created
- antigen recognised by the antibody is injected into a mouse or other mammal
- the mouse’s immune system makes plasma B cells that are capable of producing the desired antibody
- plasma cells are removed from the spleen of the mouse and fused with cancer cells called myeloma cells
describe how pregnancy tests work with a diagram
kits use monoclonal antibodies to detect hCG, which is produced during pregnancy by the developing embryo and the placenta. the urine of pregnant women contains detectable levels of hCG
- free monoclonal antibodies specific to hCG are conjugated to an enzyme that changes the colour of a dye
- a second set of monoclonal antibodies specific to hCG are immobilised to the dye substrate
- if hCG is present in urine, it will interact with both sets of monoclonal antibody (forming an antibody ‘sandwich’)
- when both sets of antibody are bound to hCG, the enzyme is brought into physical proximity with the dye, changing its colour
- a third set of monoclonal antibodies will bind any unattached enzyme-linked antibodies, functioning as a control
function of bones and exoskeletons
provide anchorage for muscles and act as levers
define exoskeletons
external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects
describe a first class lever and give an example
E (down), F, R (up)
Example - when a person nods their head backwards
describe a second class lever and give an example
F, R, E (down)
Example - someone walking, the moment where they stand on their tiptoes.
describe a third class lever and give an example
F, E (up), R (down)
Example - flexing forearm down
skeletal muscles are
antagonistic
define antagonistic muscles
when one muscle contracts, the other relaxes - they thus produce opposite movements at a joint
give a example of an antagonistic muscle pair
in the elbow, the triceps extends the forearm while the biceps flex the forearm
give an example of antagonistic pairs of muscles in an insect
in the leg of a grasshopper, which is specialised for jumping.
- when the grasshopper prepares to jump, the flexor muscles will contract
- this will bring the tibia and tarsus into a position where they resemble the letter Z and the femur and tibia are brought closer together (flexing). extensor muscles relax during this phase
- extensor muscles contract extending the tibia and producing a powerful propelling force.
draw a diagram of insect legs and their antagonistic muscle pairs
478
draw a diagram of a human flow as an example of a synovial joint
define a synovial joint
a freely moveable joint that allows a wide range of movement (articulation)
cartilage
- tough, smooth tissue that covers the regions of bone in the joint
- prevents contact between regions of bone that might otherwise rub together, helping prevent friction
- absorbs shocks that might cause bones to fracture
synovial fluid
- fills a cavity in the joint between the cartilages on the ends of the bones
- lubricates the joint so helps to prevent the friction that would occur if the cartilages were dry and touching
joint capsule
- tough ligamentous covering to the joint
- seals the joint and holds in the synovial fluid
- helps prevent dislocation
radius bone
to which the biceps is attached
biceps
flexes the joint
humerus bone
to which the biceps and triceps are attached
triceps
extends the joint
ulna bone
to which the triceps is attached
synovial joints allow
certain movements but not others
what determines the movements that are possible in a body part?
the structure of a joint, including the joint capsule and the ligaments