Plant responses and the brain

Sample questions

Original practice questions written in the style of the exam.

1. Question 14 marks

   Explain how a plant shoot bends towards light coming from one side.

   Mark scheme

   • Auxin (IAA) is produced in the shoot tip (1)
   • Auxin moves to / accumulates on the shaded side of the shoot (1)
   • Auxin stimulates cell elongation on the shaded side (by causing H⁺ to be pumped into cell walls, loosening them) (1)
   • Cells on the shaded side elongate more than on the lit side, so the shoot bends towards the light (1)
2. Question 23 marks

   A doctor wants to find out which regions of a patient's brain are active while the patient speaks.

   Explain why functional magnetic resonance imaging (fMRI) is more suitable than computed tomography (CT) for this purpose.

   Mark scheme

   • fMRI detects changes in blood flow / oxygenated haemoglobin to active brain regions (1)
   • So it shows brain activity in real time while the patient carries out a task (1)
   • CT only shows structure from a single image (and exposes the patient to X-rays), not activity (1)