Practicals Flashcards
This frog can exchange gases across the surfaces of both the skin and the lungs.
A scientist investigated the percentage of the gases exchanged at each surface
Deduce why the skin and the lungs of this frog are involved in the exchange
of oxygen.
gas exchange by {skin/lungs} alone is insufficient / both surfaces are required for sufficient diffusion of oxygen because surface area : volume is too small
metabolic reactions would not be able to occur at required rate with one surface
Explain the advantages of using this type of frog with a translucent underside for the investigation of the percentage of the gases exchanged at each surface
transparent body / translucent skin means) heart is visible / monitoring of heart rate is non-invasive
aquatic animal therefore caffeine can diffuse from solution into frog through the skin
State and justify a suitable control for this investigation on effect of caffeine concentration on the heart rate of ghost shrimps
pond/plain water used
to compare with the caffeine solutions / to show normal/ resting / starting heart rate
state and justify variables relating to caffeine solution
temperature/ aeration of solution
temperature - cold may reduce hr
state and justify variables relating to ghost shrimp
same sex/age/size of shrimp
so caffeine would affect the ghost shrimp equally
explain an advantage to using ghost shrimp for the
transparent body - makes procedure non-invasive/ heart is visible
aquatic organism - can take in caffeine from solution
invertebrate - less likely to feel pain
Explain why betalain molecules cannot move through intact cell membranes.
too large to move through membrane
no carrier/channel proteins for betalains to move through
betalains are polar and are repelled by the hydrophobic fatty acid tails
explain how to devise a procedure on the effect of increasing the concentration of detergent.
use beetroot cores
soak in distilled water and pat dry to remove excess pigment
use range of detergent concentrations from 0% / 0.2%
control age of beetroot cores
use a colorimeter to measure absorbance
use a water bath to control temperature
same amount of time in solution
Name a piece of apparatus that would be used to measure the light
absorbance of a mixture.
colorimeter
Milk at the start of a feed does not contain any vitamin C. Milk at the end of a
feed can contain 10 mg of vitamin C per 100 cm3 of milk.
Milk samples were taken at different times during the course of one feed.
Devise a method to measure how the concentration of vitamin C changes during
the course of a feed
five samples of breast milk tested from different points of feed
titration of breast milk using DCPIP
standardisation of titration technique use of a calibration curve to determine the vitamin C content in each breast milk sample
repeat titration to achieve concordant results (for each time)
A method for pickling red onions is to immerse them in wine vinegar. This vinegar
contains ethanoic acid. The vinegar causes anthocyanin pigments to leave the onion
cells, entering the solution.
Explain why pickling in vinegar would result in anthocyanin pigments leaving the
onion cell
increased permeability of (cell surface) membrane
the low pH would denature proteins in cell surface membrane
as vinegar bonds in protein
vinegar could dissolve lipids in cell surface membrane
Devise an investigation that can be used to collect data on the vitamin C concentration of five fruit juices
titration using DCPIP
use same volume of fruit juice/DCPIP
control age of fruit juice
DCPIP changes from blue to colourless when it comes into contact with vitamin c
compare result with standardised vitamin C solution / use a calibration curve
explain advantages of using young zebrafish when investigating effect of caffeine on the heart rate
transparent body - so heart is visible/ procedure is non-invasive
aquatic organism - therefore can take in caffeine from solution
Give one reason why a different ethical issue has to be considered when using
zebrafish instead of Daphnia in this investigation.
zebrafish are vertebrates therefore they are more likely to
feel pain
The hydrolysis of collagen results in a decrease in pH. The indicator
phenolphthalein is pink at pH 8 and becomes colourless at lower pH values.
Devise an investigation to determine the effect of arazyme concentration on
the rate of hydrolysis of collagen.
at least five different concentrations of arazyme solution a controlled variable
measuring of the dependent variable time taken for phenolphthalein)
to decolourise replicates / repeats for each arazyme concentration to allow
calculation of mean values
A student investigated the following hypothesis:
‘The permeability of cell membranes in a red cabbage leaf is affected by the age
of the plant.’
Devise an investigation the student could use to test this hypothesis and collect
valid data
cabbage leaves of at least 5 differently aged plants used
all have same surface area
temperature of growing environment controlled
use a colorimeter to measure permeability
repeat each age to allow for calculation of each mean
Three males of the same age were given cups of coffee containing caffeine. Their
heart rates were measured 10 minutes after drinking the coffee.
Two hours later they were given cups of coffee with no caffeine and after 10 minutes
their heart rates were measured
describe how this investigation could be improved
need to take into account resting heart rate
include females in sample
include a range of ages in the sample
take into account previous coffee habits
heart rate is also affected by exercise so habits need to be taken into account
