CAIE A-Level Biology M.1 Prefixes, Units, Symbols and Standard Form

Practise converting biological measurements between prefixes, selecting valid units and expressing very large or small quantities in standard form.

[Maximum number: 1]

Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.

When viewed in longitudinal section (LS), smooth muscle cells are elongated and taper at both ends. This is known as a fusiform shape. Each cell has a central nucleus, which also appears elongated.

Fig. 1.1 is a diagram of a smooth muscle cell to show the fusiform shape.

Fig. 1.1

A student used a microscope fitted with a calibrated eyepiece graticule to estimate that the length of one smooth muscle cell was 250 micrometres $(\mu \mathrm{m})$ .

The smallest object the student can see without the use of a microscope is 0.2 mm in length.

Explain whether the student would be able to see a cell of length $250 \mu \mathrm{~m}$ without the use of a microscope.

yes, qualified ; e.g.

$0.2 \mathrm{~mm}=\underline{200 \mu \mathrm{~m}}$

0.2 mm / smallest student can see, is less than 0.25 mm

$250 \mu \mathrm{~m}=\underline{0.25 \mathrm{~mm}}$ $250 \mu \mathrm{~m}$ / cell length, is longer than $200 \mu \mathrm{~m}$

the cell is $50 \mu \mathrm{~m}$ longer (than 0.2 mm )

the cell is 0.05 mm longer (than 0.2 mm )

Marking guidance:

allow if converted to standard form ( $2 \times 10^{-4} \vee 2.5 \times 10^{-4} \mathrm{~m}$ )

must have units

must include numerical values

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M.1—Prefixes, units, symbols and standard form question 1