June 2018

Question 1

1.3. Some types of cell contain special proteins called chaperones. They’re mostly found on the ER.
Describe the role of chaperone proteins. (2)

Answer 1

(1) they bind to hydrophobic groups
(2) to prevent incorrect hydrophobic interactions / allow protein to be correctly folded

Question 2

1.4. A protein in a eukaryotic cell may have a different shape from a protein in a bacterium even though they’re coded for by an identical gene. Why? (1)

Answer 2

(1) bacteria don’t have ER

Question 3

2.2. Exp=effect of temp. on the permeability of membranes in beetroot cells.
Explain why as the temp increases, the colour of the liquid becomes darker. (3)

Answer 3

(1) because the membrane’s permeability increases
(2) as the phospholipids/proteins = gain KE and move more
(3) Betanin/red pigment = gains KE and diffuses faster

Question 4

2.4. Exp=effect of temp. on the permeability of membranes in beetroot cells.
The student repeated the experiment at 100°C and found that the colour of the liquid was the same as the colour at 85°C. Why? (2)

Answer 4

(1) the membrane is destroyed/ disrupted/ denatured
(2) max. amt of pigment diffused into liquid / conc. of pigment has reached equilibrium

Question 5

2.5. Exp=effect of temp. on the permeability of membranes in beetroot cells.
Suggest one suitable control group for this experiment. (1)

Answer 5

(1) boiled beetroot cubes

Question 6

2.6. Exp=effect of temp. on the permeability of membranes in beetroot cells.
All of the beetroot pieces were cut to the same shape and size. Why? (2)

Answer 6

(1) keep the SA:V ratio the same / constant
(2) to ensure the only variable affecting the Rate of diffusion is temp.

Question 7

3.2. State 2 ways in which the structure of mitochondrial DNA is different from the structure of DNA inside the nucleus. (2)

Answer 7

(1) it’s shorter
(2) has no introns

Question 8

3.3. Explain one way, other than using DNA, in which genetic diversity could be measured. (2)

Answer 8

(1) the amino acid sequence of a protein
(2) the greater the number of differences in the sequence, the greater the GD

Question 9

3.4. Studying the Genetic diversity of parasitic flatworms is important in reducing the number of deaths caused by schistosomiasis. Why? (1)

Answer 9

(1) to develop medicine to treat the disease.

Question 10

5.6. Explain how the structure of cellulose is related to its role in plant cell walls (3)

Answer 10

(1) forms long / straight / unbranched chains
(2) forming microfibrils/ many hydrogen bonds between chains
(3) provide rigidity / strength/ support

Question 11

6.3. Exp= the effect of pH on the rate of browning of apples.
Explain why having a colour standard is an improvement to the exp. (2)

Answer 11

(1) to compare pieces of apple at diff. pHs to the standard
(2) so that there’s more consistency

Question 12

8.4. Fireflies that have a flash length between 0.7 and 0.8 seconds are less likely to pass their alleles on to the next generation (they’re a small population). Why? (2)

Answer 12

(1) these males are more likely to accidentally mate/form hybrids with females of a different species
(2) hybrids are non-fertile