A-level BIOLOGY Paper 3

A-level BIOLOGY Paper 3 Wednesday 21 June 2023 Morning Time allowed: 2 hours Materials For this paper you must have: • a ruler with millimetre measurements • a scientific calculator. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions in Section A. • Answer one question from Section B. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Show all your working. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for the questions are shown in brackets. • The maximum mark for this paper is 78. Section A Answer all questions in this section. You are advised to spend no more than 1 hour and 15 minutes on this section. box . Describe how stimulation of a Pacinian corpuscle produces a generator potential. [3 marks] Scientists investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip. The scientists applied two different pressures to the fingertip and recorded the changes in membrane potential of the Pacinian corpuscle’s sensory neurone. Figure 1 shows the scientists’ results. Figure 1 . Use Figure 1 to describe what is meant by the all-or-nothing principle. [2 marks] box . On Figure 1, from 0.6 ms to 4.0 ms, no new generator potential could be produced. What is this time period called? [1 mark] Turn over for the next question