Pearson International A Level Biology Core Practical 18: Investigate amylase production in germinating cereal grains

This core practical is part of Pearson's practical-learning programme. The method below is one defensible implementation, not a confidential instruction sheet. Centres may adapt equipment while preserving the scientific purpose, controls, measurements and safety requirements.

Aim and scientific principle

Compare amylase activity in matched cereal grains at defined germination stages using a standardised starch assay.

Begin by translating the title into a testable question. Identify what is deliberately changed, what is measured directly, what is calculated and what must remain controlled. Predict a relationship only after naming the mechanism. A prediction without a reason is weak; a reason without measurable variables cannot guide a practical design.

Apparatus and setup

Use matched germinating and non-germinated cereal grains, extraction buffer, balance, mortar and pestle, pipettes, starch agar or a standardised starch solution, iodine reagent, incubator or water bath and measuring equipment. Select instruments by range and resolution. Include a heat-inactivated extract or buffer control to identify non-enzymic starch loss.

Before collecting results, check zero readings, calibration, leaks, alignment or sterility as relevant. Record the instrument resolution beside the first raw-data table. If a digital device displays more digits than its underlying accuracy supports, do not treat every digit as equally certain.

Method

1. Germinate matched grain groups for defined times or under the specified treatment, alongside a non-germinated control.
2. Homogenise equal grain mass with equal buffer volume and clarify extracts consistently.
3. Apply equal extract volumes to identical starch assays and incubate for the same time at controlled pH and temperature.
4. Add iodine where required, measure the cleared area or residual starch response and compare independent grain groups.

Plan the analysis before starting. This reveals whether an additional measurement is needed for a derived quantity and prevents a completed experiment from lacking a mass, length, concentration, background or calibration value. A method should be detailed enough for another trained student to reproduce, while avoiding decorative steps that do not affect validity.

Variables and controls

• Independent variable: germination time or cereal-grain condition.
• Dependent variable: cleared-zone area, residual starch response or another calibrated measure of amylase activity.