BIOL1 Flashcards
in these patients, the right ventricle still produces sufficient blood flow to keep the patient alive. suggest why the left ventricle requires the help of the artificial heart but the right ventricle does not. (2)
- left ventricle pumps to whole body
- left ventricle produces a greater pressure
the pulse felt in the artery in the wrist can be recorded and used to measure heart rate. suggest why the pulse can be used to measure heart rate. (2)
- caused by pressure
- from one contraction of left ventricle
the portable heart rate monitor recorded the men’s heart rates continuously. this gave more reliable mean heart rates than those obtained by recording the pulse in the wrist for 1 minute. suggest why it is more reliable (2)
- monitor records over long period of time
- anomalies in recording have less effect
people with AIDS die because they are unable to produce an immune response to pathogens. explain why this leads to death. (3)
- susceptible to other pathogens
- pathogens reproduce
- damage cells
HIV rapidly enters host cells. explain why that a vaccine might not be effective against HIV. (2)
- HIV enters cells before antibodies can bind to it
- antibodies cannot enter cells
HIV shows a lot of antigenic variability. explain why that a vaccine might not be effective against HIV. (2)
- antigen on HIV changes
- antibody can no longer bind to new antigen
describe the induced fit model of enzyme action. (2)
- active site not complementary
- active site changes
- change in enzyme allows E-S complexes to form
describe one way that the lock and key model is different from the induced fit model. (1)
- active sire does not change shape
explain, interms of pressure, why the semilunar valves open. (1)
- pressure is greater in ventricle than artery
when a wave of electrical activity reaches the AVN, there is a short delay before a new wave leaves the AVN. explain the importance of this short delay. (2)
- allows ventricles to fill
- before ventricles contract
before reweighing the student blotted dry the outside of each potato cylinder. explain why. (2)
- water will affect the mass
- amount of water on cylinders varies
the student calculated the percentage change in mass rather than the change in mass. explain the advantage of this. (2)
- allows comparison
- cylinders have different starting masses
the student carried out several repeats at each concentration of sodium chloride. explain why the repeats were important. (2)
- allows anomalies to be identified
- makes mean more reliable
The vaccine is made from HPV types 16 and 18. explain why this vaccine may not protect against other types of this virus. (3)
- other HPV types have different antigens
- no memory cells for other types
- antibodies not complementary
3 injections of the vaccine are given. use your knowledge of immunity to suggest why. (3)
- More antigen;
- More memory cells;
- So antibodies produced quicker if infected
it will be many years before it can be shown that this vaccination programme has reduced cases of cervical cancer. suggest 2 reasons why. (2)
- cancer takes years to develop
- only teenagers vaccinated