Exam questions Flashcards
Give four reasons why a contemporary drug testing protocol is an improvement on the trial used by William Withering (4)
safe:
- due to pre drug trails on {cells/animals} before testing on humans
- more regulated legislation
valid:
- placebo is used as a comparison
- double blind trial is used
- control factors are used such as cohort, age, lifestyle
reliable:
- more people are tested on
- results are analysed statistically
Explain why some bacteria can grow rapidly in skin wounds (3)
- temperature is warm, increasing the rate of reactions in bacteria
- availability of energy source from blood/tissue
- availability of water for bacterial cell function
- oxygen for aerobic respiration to occur
Explain why healthy volunteers were given different doses of the drug or a placebo (2)
- to check for ay side effects
- use different dosages to determine a safe dose
Compare and contrast the modern drug testing protocol with that used by William Withering when he tested digitalis soup (3)
- both trials used different doses to determine a safe dose
- Withering did not use healthy volunteers whereas the modern trails do
- Withering did not use a placebo whereas the modern trials do
Explain why placebos are used to test the efficiency of new drug treatments (2)
- inactive substance used
- used as a control (comparison to actual drug)
- phycological effect of taking drug or placebo
Explain what is meant by a double blind trial (2)
- one set of patients given new drug other set are given the placebo
- nether patient nor doctor know which treatment given to the patients
- removes bias from the results
Describe and explain the procedures that must be followed before drugs can be tested on patients (3)
- test on animals or tissue cultures
- to test if the drug is toxic
- test on healthy volunteers
- to test for side effects
Describe the three clinical trail phases (3)
- phase I is tested on a small number of healthy volunteers
- phase II is tested on a small number of patients with the disease
- phase III the drug is tested on a large number of patients with the disease
- reference to {placebo/double blind trial} during phase II/III
State what is meant by the term tensile strength (1)
the force a fibre can withstand before breaking
Suggest why calcium ions affect the tensile strength of plant fibres (2)
- calcium pectate
- middle lamella
- holding together microfibrils in the cell wall
- fibres are stronger if cellulose microfibrils are held together more strongly
Explain the role of calcium ions in the structure of cell walls in plants (2)
- calcium needed for calcium pectate
- holds cellulose microfibrils in a matrix
- reference to middle lamella
Describe how to carry out an investigation to determine the concentration of calcium ions needed for the maximum yield of grain from wheat plants (5)
- control variables such as {source, age, size}
- range of 5 different calcium ion concentrations
- soil solution with same pH/concentrations of other mineral ions
- environmental control variables {temperature, light intensity, humidity}
- measure {mass of grain/yield}
- repeat 5 times at each concentration/calculate the mean
Explain how secondary thickening in the cell wall contributes to the physical properties of xylem vessels (3)
- provides greater tensile strength
- provides {extra rigidity/reduced flexibility}
- lignin provides waterproofing
- pits present for movement of water in/out of xylem
Explain what is meant by the term antimicrobial properties (1)
ability to {kill/slow the growth} of {bacteria/microorganisms}
Explain why the two halves of the Petri dish are not completely sealed with sticky tape (2)
- allows oxygen in
- oxygen is required for aerobic respiration by bacteria
- conditions not encouraging the growth of pathogenic bacteria
Suggest a suitable temperature for the safe incubation of the agar plates in a school laboratory. Give an explanation for your answer (2)
- appropriate temperature 25°C (20°C-30°C)
- above 37°C promotes the growth of pathogenic bacteria
Describe two aseptic techniques that should be used when working safely with bacteria (2)
- flame/disinfect the instruments
- autoclave used plates
- disinfect bench before and after working
Describe how the antimicrobial properties of the seeds of a plant could be tested
- extract made from the plants seeds
- agar plate with bacteria (E.coli)
- description of aseptic technique
- plant extract placed on microbiology discs
- control described (5mm discs used)
- incubate at 25°C for 24 hours
- look for zone of inhibition
- repeat experiment 5 times and calculate the mean
Explain what is meant by zone of inhibition (1)
area where there is no bacteria/bacteria not growing
Name three inorganic ions that could be contained in the fertilisers and explain how these would improve the yield of the crop plants (4)
- nitrate ions, calcium ions, magnesium ions
- nitrate ions used for {proteins/amino acids}
- proteins used for growth
- calcium ions to {strengthen cell walls}
- magnesium ions for chlorophyll production
- chlorophyll used for photosynthesis
Explain how calcium, nitrate and magnesium ions are used by plants (3)
- nitrate for the production of {amino acids/protein/DNA}
- calcium for {calcium pectate/middle lamella}
- magnesium for the production of chlorophyll
Explain the effects of a shortage of magnesium ions on a plant (3)
- limits the production of chlorophyll
- lack of {glucose} due to less photosynthesis
- stunted growth and yellow leaves
Describe the structure of plasmodesmata (2)
- pores in the cell walls between adjacent cells
- cytoplasm runs though the plasmodesmata
Describe the structure of a cellulose microfibril (4)
- contains beta glucose
- glucose molecules joined by condensation reactions
- only 1-4 glycosidic bonds
- every alternate beta glucose molecule is inverted
- {unbranched/straight} chain
- microfibril composed of 60-70 cellulose chains
- cellulose chains held together by hydrogen bonds
