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CAIE A-Level Biology A2 P5.2 Planning Experimental Methods Questions

Use these questions to justify comparison groups and reference controls, keep starting conditions consistent, and sequence practical techniques so the evidence can test a stated hypothesis.

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • Vary the independent variable across clear comparison treatments and include suitable control or baseline groups.
  • Standardise conditions and use a reference endpoint so treatments begin comparably and changes can be judged.
  • Sequence sampling and analytical techniques so the resulting comparison can test the stated hypothesis.

CAIE A-Level Biology A2 P5.2 Planning Experimental Methods Questions question 1

[Maximum number: 4]

The light dependent stage of photosynthesis in a suspension of isolated chloroplasts can be investigated using the Hill reaction.

Dichlorophenolindophenol (DCPIP) can be used to follow the process. DCPIP is a blue dye which turns colourless when it is reduced by accepting hydrogen and electrons.

 oxidised DCPIP → reduced DCPIP  blue → colourless \begin{array}{clc} \text { oxidised DCPIP } & \rightarrow & \text { reduced DCPIP } \\ \text { blue } & \rightarrow & \text { colourless } \end{array}

Explain the reasons for:
the colour standard tube A
covering the beaker containing the chloroplast-DCPIP mixture with foil.

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