AQA
A-Level
BIOLOGY
3.2a Cells
2.8-2.9 | Transport across Cell Membranes
Time allowed
60 minutes
MARK SCHEME
Score Percentage
/49 %
4.1 | CELL BIOLOGY | QUESTION PAPER 1 1
, .(a) Calculations made (from raw data) / raw data would have recorded initial and final
masses.
1
(b) Add 4.5 cm3 of (1.0 mol dm–3) solution to 25.5 cm3 (distilled) water.
If incorrect, allow 1 mark for solution to water in a proportion
of 0.15:0.85
2
(c) 1. Water potential of solution is less than / more negative than that of
potato tissue;
Allow Ψ as equivalent to water potential
2. Tissue loses water by osmosis.
2
(d) 1. Plot a graph with concentration on the x-axis and percentage change in
mass on the y-axis;
2. Find concentration where curve crosses the x-axis / where percentage
change is zero;
3. Use (another) resource to find water potential of sucrose concentration
(where curve crosses x-axis).
3
[8]
A-Level
BIOLOGY
3.2a Cells
2.8-2.9 | Transport across Cell Membranes
Time allowed
60 minutes
MARK SCHEME
Score Percentage
/49 %
4.1 | CELL BIOLOGY | QUESTION PAPER 1 1
, .(a) Calculations made (from raw data) / raw data would have recorded initial and final
masses.
1
(b) Add 4.5 cm3 of (1.0 mol dm–3) solution to 25.5 cm3 (distilled) water.
If incorrect, allow 1 mark for solution to water in a proportion
of 0.15:0.85
2
(c) 1. Water potential of solution is less than / more negative than that of
potato tissue;
Allow Ψ as equivalent to water potential
2. Tissue loses water by osmosis.
2
(d) 1. Plot a graph with concentration on the x-axis and percentage change in
mass on the y-axis;
2. Find concentration where curve crosses the x-axis / where percentage
change is zero;
3. Use (another) resource to find water potential of sucrose concentration
(where curve crosses x-axis).
3
[8]
