Plant tissue gains 4% mass at 0.20 mol/dm³ sugar and loses 4% at 0.40 mol/dm³. Assume a linear relationship between these points.
.1
Estimate the concentration giving zero net mass change.
[2 marks]
.2
Explain what zero net change means and how to improve the estimate.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A class plans to investigate how light intensity affects photosynthesis using pondweed, a lamp, a ruler, a water bath and a gas-collection syringe.
Plan an investigation that produces valid, repeatable rate comparisons.
[6 marks]
5 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A flask of yeast and glucose releases 18 cm³ carbon dioxide in 6 minutes at 30 °C and 3 cm³ in 6 minutes at 60 °C. A student says yeast respires fastest at any higher temperature.
.1
Calculate the ratio of the rate at 30 °C to the rate at 60 °C, expressed as a number of times.
[2 marks]
.2
Evaluate the student's claim.
[3 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
Equal masses of fat are mixed with equal lipase concentrations at 37 °C. A has large droplets at pH 3; B has large droplets at pH 8; C has small droplets at pH 8. This lipase works best near pH 8.
.1
Explain why B should digest fat faster than A.
[2 marks]
.2
Explain why C should be faster than B and relate this to bile.
[2 marks]
4 marksHigher
Spec and skills
Original practice question
Answer and supported method checks
A model of hormonal contraception keeps oestrogen and progesterone at concentrations that inhibit FSH and LH.
.1
Explain how this model reduces the chance of pregnancy.
[3 marks]
.2
Explain why this hormone model does not predict protection from sexually transmitted pathogens.
