A Level Biology Paper 3 Exam with Questions and Answers – 100% Solved
Describe the graph that can be plotted from the results of this practical. - ✔✔✔-A bar chart of
zone of inhibition against antibiotic.
Explain the change in mass in the potato chips. - ✔✔✔-The potato chips with concentration
lower than the sucrose solution (higher water potential) lose mass as there is a net movement
of water out of the cells.
The potato chips with concentration higher than the sucrose solution (lower water potential)
gain mass as there is a net movement of water into the cells.
How are the results used to calculate the rate of respiration at each temperature? - ✔✔✔-Rate
= 1 / time taken for methylene blue to decolourise
How can a choice chamber be used to measure the favourable environment of a small
organism? - ✔✔✔-By setting up chambers in different quadrants with different environmental
conditions: dark + dry, dark + damp, light + dry, light + damp
Organisms will move to the quadrant they find favourable
How can Benedict's solution be used to measure the concentration of glucose in a solution? -
✔✔✔-Use a colorimeter to measure the absorbance of a series of solutions of known
concentrations to create a calibration curve. Compare the absorbance of an unknown sample to
the calibration curve.
How can the results be used to determine the relationship between the chosen factor and the
percentage cover? - ✔✔✔-Spearman's rank - correlation
How can the results of the practical measuring enzyme activity be used to find the initial rate of
reaction? - ✔✔✔-Plot your results on a graph of 'rate of reaction' against 'time'.
Draw a tangent at time = 0 to find the initial rate.
, A Level Biology Paper 3 Exam with Questions and Answers – 100% Solved
How can you compare the effectiveness of different antibiotics applied to the same bacteria? -
✔✔✔-Measure the diameter and calculate the area of the zone of inhibition (clear zone) on the
agar.
How can you increase the accuracy of the estimate of the unknown glucose solution? - ✔✔✔-
Increase the number of concentrations (at smaller intervals) for the calibration curve within the
range of concentrations that the unknown solution belongs in.
How is a calibration curve used to find the concentration of plant tissue? - ✔✔✔-Plot a
calibration curve of percentage change in mass against concentration. Find the x-intercept
where the plant tissue is isotonic to the sucrose solution.
How is a control set up in a practical measuring enzyme activity? - ✔✔✔-Replace the enzyme
solution with distilled water or boiled enzyme solution.
How is beetroot used to measure the permeability of cell membranes? - ✔✔✔-The higher the
permeability, the more red pigment that leaks out into the surrounding solution within a given
time. A colorimeter can be used to determine the absorbance, hence concentration of pigment.
How is light intensity controlled? - ✔✔✔-Adjust the distance of the lamp from the set up.
Perform the practical in a dark room so that the only light source is the lamp.
How is percentage cover calculated? - ✔✔✔-Use a quadrat with squares. Count how many
squares the required species is present in. Only count a square if more than half of the square is
covered. Calculate the percentage of squares the species is present in.
How is the control set up? - ✔✔✔-Fill a cuvette with chloroplast extract and distilled water.
How is the rate of reaction calculated from time? - ✔✔✔-Rate of reaction = 1/time
Describe the graph that can be plotted from the results of this practical. - ✔✔✔-A bar chart of
zone of inhibition against antibiotic.
Explain the change in mass in the potato chips. - ✔✔✔-The potato chips with concentration
lower than the sucrose solution (higher water potential) lose mass as there is a net movement
of water out of the cells.
The potato chips with concentration higher than the sucrose solution (lower water potential)
gain mass as there is a net movement of water into the cells.
How are the results used to calculate the rate of respiration at each temperature? - ✔✔✔-Rate
= 1 / time taken for methylene blue to decolourise
How can a choice chamber be used to measure the favourable environment of a small
organism? - ✔✔✔-By setting up chambers in different quadrants with different environmental
conditions: dark + dry, dark + damp, light + dry, light + damp
Organisms will move to the quadrant they find favourable
How can Benedict's solution be used to measure the concentration of glucose in a solution? -
✔✔✔-Use a colorimeter to measure the absorbance of a series of solutions of known
concentrations to create a calibration curve. Compare the absorbance of an unknown sample to
the calibration curve.
How can the results be used to determine the relationship between the chosen factor and the
percentage cover? - ✔✔✔-Spearman's rank - correlation
How can the results of the practical measuring enzyme activity be used to find the initial rate of
reaction? - ✔✔✔-Plot your results on a graph of 'rate of reaction' against 'time'.
Draw a tangent at time = 0 to find the initial rate.
, A Level Biology Paper 3 Exam with Questions and Answers – 100% Solved
How can you compare the effectiveness of different antibiotics applied to the same bacteria? -
✔✔✔-Measure the diameter and calculate the area of the zone of inhibition (clear zone) on the
agar.
How can you increase the accuracy of the estimate of the unknown glucose solution? - ✔✔✔-
Increase the number of concentrations (at smaller intervals) for the calibration curve within the
range of concentrations that the unknown solution belongs in.
How is a calibration curve used to find the concentration of plant tissue? - ✔✔✔-Plot a
calibration curve of percentage change in mass against concentration. Find the x-intercept
where the plant tissue is isotonic to the sucrose solution.
How is a control set up in a practical measuring enzyme activity? - ✔✔✔-Replace the enzyme
solution with distilled water or boiled enzyme solution.
How is beetroot used to measure the permeability of cell membranes? - ✔✔✔-The higher the
permeability, the more red pigment that leaks out into the surrounding solution within a given
time. A colorimeter can be used to determine the absorbance, hence concentration of pigment.
How is light intensity controlled? - ✔✔✔-Adjust the distance of the lamp from the set up.
Perform the practical in a dark room so that the only light source is the lamp.
How is percentage cover calculated? - ✔✔✔-Use a quadrat with squares. Count how many
squares the required species is present in. Only count a square if more than half of the square is
covered. Calculate the percentage of squares the species is present in.
How is the control set up? - ✔✔✔-Fill a cuvette with chloroplast extract and distilled water.
How is the rate of reaction calculated from time? - ✔✔✔-Rate of reaction = 1/time
