A Level Edexcel Biology B – Core Practicals Exam Questions with Complete Solutions (Updated
2025/2026)
Justify how would you set up a respirometer to measure the rate of anaerobic respiration in
yeast? -in boiling tube put 5 cm3 of yeast
-5 cm3 of glucose solution so yeast has supply of glucose for respiration
-thin later of vegetable oil to provide barrier to oxygen
-draw coloured liquid to the end of the tube as the coloured liquid will move away as CO2 is
produced
What are the type of pigments found in chloroplasts? Primary pigments and accessory
pigments:
-carotene (orange)
-phaeophytin (grey)
-xanthophyll (yellow)
-chlorophyll a (blue-green)
-chlorophyll b (yellow-green)
What is the purpose of having accessory pigments? plants have additional pigments (besides
chlorophyll) so they can gather energy from more wavelengths of light
Why is sodium hydrogen carbonate added to pondweed in a beaker when measuring the effect
of different wavelengths of light on photosynthesis? provides pondweed with a source of
carbon dioxide
Outline an investigation to find the effects of different wavelengths on the rate of
photosynthesis 1. place piece of pondweed in a beaker of water
2. cover one side of beaker with aluminium foil so that light can only enter the beaker from the
other side
3. add half a spatula of sodium hydrogen carbonate to water and leave for 5 minutes
,4. position bench lamp close to beaker with a colourless filter between the lamp and beaker.
This will be a white light control. Allow pondweed to adjust for 5 minutes.
5. fill the capillary tubing of the photosynthometer with water
6. place funnel end of tubing into beaker of water and add the pondweed, positioning it with
the cut end at the top in the funnel opening.
7. as bubbles of oxygen begin to form and pass into the capillary tube, start the stop clock. After
suitable time draw up any oxygen produced into syringe. Record volume of gas produced
8. Replace the filter with another filter or a different colour and leave for five minutes
9. Refill capillary tube using syringe and then begin recording again
What are the control variables when investigating the effect of wavelength of light on
photosynthesis? -light intensity
-temperature
-amount of sodium hydrogen carbonate
-time allowed for gas collection
What is the purpose of chromatography? to separate different components in a sample.
State the factors affecting the rate of migration of different pigments -solubility
-affinity for the paper
-mass
What is the formula for Rf value? Rf value = Distance travelled by substance / Distance
travelled by solvent
What is the purpose of finding the Rf value of a pigment? -experimental Rf value can be
compared to Rf value in a data base to identify the pigment
-the standard value should be using the paper and the solvent
, What is standard deviation? a computed measure of how much scores vary around the mean
score
What is a serial dilution? used to obtain a series of solution whose concentrations differ by
known amounts
Why do we measure initial rate of reaction? Reaction can be controlled, as when reaction starts
substrate concentration will decrease fast
What does catalase catalyse? break down of hydrogen peroxide to water and oxygen gas
What does copper sulphate do to catalase? acts as a non completive inhibitor slowing
production of oxygen
What effect will higher concentrations of copper sulphate have on a downward displacement of
water experiment, measuring oxygen produced from hydrogen peroxide and catalase? higher
concentrations will cause less oxygen production as copper sulphate inhibit the activity of
catalase so less oxygen is broken down
What are the four factors that affect enzyme activity? -enzyme concentration
-substrate concentration
-pH
-temperature
Why do higher trypsin concentrations cause the colorimeter to decrease in absorbance faster?
higher trypsin concentrations means more enzymes available making collisions with
substrate more likely, this breaks down protein in milk, causing it to lose its white colour faster,
therefore less light is absorbed by solution
2025/2026)
Justify how would you set up a respirometer to measure the rate of anaerobic respiration in
yeast? -in boiling tube put 5 cm3 of yeast
-5 cm3 of glucose solution so yeast has supply of glucose for respiration
-thin later of vegetable oil to provide barrier to oxygen
-draw coloured liquid to the end of the tube as the coloured liquid will move away as CO2 is
produced
What are the type of pigments found in chloroplasts? Primary pigments and accessory
pigments:
-carotene (orange)
-phaeophytin (grey)
-xanthophyll (yellow)
-chlorophyll a (blue-green)
-chlorophyll b (yellow-green)
What is the purpose of having accessory pigments? plants have additional pigments (besides
chlorophyll) so they can gather energy from more wavelengths of light
Why is sodium hydrogen carbonate added to pondweed in a beaker when measuring the effect
of different wavelengths of light on photosynthesis? provides pondweed with a source of
carbon dioxide
Outline an investigation to find the effects of different wavelengths on the rate of
photosynthesis 1. place piece of pondweed in a beaker of water
2. cover one side of beaker with aluminium foil so that light can only enter the beaker from the
other side
3. add half a spatula of sodium hydrogen carbonate to water and leave for 5 minutes
,4. position bench lamp close to beaker with a colourless filter between the lamp and beaker.
This will be a white light control. Allow pondweed to adjust for 5 minutes.
5. fill the capillary tubing of the photosynthometer with water
6. place funnel end of tubing into beaker of water and add the pondweed, positioning it with
the cut end at the top in the funnel opening.
7. as bubbles of oxygen begin to form and pass into the capillary tube, start the stop clock. After
suitable time draw up any oxygen produced into syringe. Record volume of gas produced
8. Replace the filter with another filter or a different colour and leave for five minutes
9. Refill capillary tube using syringe and then begin recording again
What are the control variables when investigating the effect of wavelength of light on
photosynthesis? -light intensity
-temperature
-amount of sodium hydrogen carbonate
-time allowed for gas collection
What is the purpose of chromatography? to separate different components in a sample.
State the factors affecting the rate of migration of different pigments -solubility
-affinity for the paper
-mass
What is the formula for Rf value? Rf value = Distance travelled by substance / Distance
travelled by solvent
What is the purpose of finding the Rf value of a pigment? -experimental Rf value can be
compared to Rf value in a data base to identify the pigment
-the standard value should be using the paper and the solvent
, What is standard deviation? a computed measure of how much scores vary around the mean
score
What is a serial dilution? used to obtain a series of solution whose concentrations differ by
known amounts
Why do we measure initial rate of reaction? Reaction can be controlled, as when reaction starts
substrate concentration will decrease fast
What does catalase catalyse? break down of hydrogen peroxide to water and oxygen gas
What does copper sulphate do to catalase? acts as a non completive inhibitor slowing
production of oxygen
What effect will higher concentrations of copper sulphate have on a downward displacement of
water experiment, measuring oxygen produced from hydrogen peroxide and catalase? higher
concentrations will cause less oxygen production as copper sulphate inhibit the activity of
catalase so less oxygen is broken down
What are the four factors that affect enzyme activity? -enzyme concentration
-substrate concentration
-pH
-temperature
Why do higher trypsin concentrations cause the colorimeter to decrease in absorbance faster?
higher trypsin concentrations means more enzymes available making collisions with
substrate more likely, this breaks down protein in milk, causing it to lose its white colour faster,
therefore less light is absorbed by solution
