A-Level Edexcel Biology AS SI Unit Prefixes

A-Level Edexcel Biology AS SI Unit Prefixes
Pearson Edexcel International Advanced Subsidiary/Advanced Level in Biology, Issue 2, February 2021Biology XBI11/YBI11

Review A-Level Edexcel Biology SI unit prefixes through graticule measurements, micrometre conversions, nanometre ratios and cell-structure sizes.

How this is tested

  • convert graticule measurements from metres to micrometres for pores or pith cells
  • compare ribosome and lysosome diameters by converting nm and µm before forming a ratio

Question 2(a)(i)

[Maximum number: 2]

Fibres from the stems of hemp plants are widely used in industry for their great tensile strength.

The relationship between tensile strength and fibre diameter was investigated.
The photograph shows a cross section of a part of a hemp fibre and an eyepiece graticule. The fibre bundle is made up of pith cells, some of which are shown here.

Figure for Question 2(a)(i) — Edexcel A-Level Biology AS

Each of the smallest units on the graticule is 3×10−6 m3 \times 10^{-6} \mathrm{~m}.

Calculate the width of the pith cell labeled A in micrometres ( μm\mu \mathrm{m} ).

Answer μm\mu \mathrm{m}