Paper 1 exam questions Flashcards
Explain why the scientists used the same restriction endonuclease enzymes on
each DNA sample.
Cut (DNA) at same (base) sequence / (recognition) sequence;
Accept: cut DNA at same place
2. (So) get (fragments with gene) R / required gene.
Accept: ‘allele’ for ‘gene’ / same gene
A scientist studied the growth of Salmonella.
(i) Salmonella was isolated from a mixed culture of bacteria, using streak plating
onto selective media.
Explain why this is a suitable method for isolating the Salmonella
medium allows only {Salmonella / certain bacteria} to grow
(1)
{culture / colonies / bacteria} is spread out on the {agar /
medium} (1)
because this separates out individual bacteria (1)
so that colonies are {discrete / separate / individual} (1)
so only one type of {bacteria / colony} can be picked up
Explain how, on a very hot day, the brain ensures that the water potential of
The blood remains constant.
sweating occurs causing loss of water from the blood (1)
* therefore the water potential of the blood falls (1)
* osmoreceptors are stimulated (1)
* causing the pituitary gland to secrete {antidiuretic hormone /
ADH} (into the blood) (1)
* causing the {collecting ducts / kidney tubules} in the kidney
to reabsorb more water (into the blood) (
Cysteine proteases are enzymes found in fruits such as pineapples.
When a protease enzyme is added to fat‑free skimmed milk, the milk turns from
cloudy to clear.
(a) Devise an investigation to find the optimum temperature for the activity of the
enzyme cysteine protease found in pineapples.
(6)
make extract of pineapple juice (1)
* same {volume of skimmed milk / volume of pineapple
juice extract} (1)
* {use colorimeter to measure changes in absorbance with
time / beaker over a black cross and time to disappear}
(1)
* calculation of initial rate (1)
* at a range of temperatures using a water bath (1)
* pH controlled using buffer (1)
