The size and scale of cells: including standard form | Combined science

Starter quiz

In which type of cell is the genetic material not enclosed within a membrane-bound nucleus?

prokaryotic cell ✓

eukaryotic cell
Which piece of apparatus is used in science laboratories to view cells?

telescope

hand lens

magnifying glass

microscope ✓
In microscopy, what does the term magnification mean?

making small objects appear larger in order to see more detail ✓

the brightness of the light source

the distance at which two distinct points of a specimen can still be seen

the size of the microscope stage
What is being described: "the distance at which two distinct points of a specimen can still be seen"?

magnification

brightness

resolution ✓

microscopy
On which part of a microscope is the specimen placed in order to view it?

'stage' ✓
What is the purpose of the objective lenses on a light microscope?

to adjust the magnification ✓

to control the amount of light

to hold the microscope slide

to provide structural support

to adjust the focus

Starting with the smallest, sort the units of measurement into increasing size order.

1

⇔

nanometres (nm)

2

⇔

micrometres (µm)

3

⇔

millimetres (mm)

4

⇔

metres (m)
How many nanometres are in a micrometre?

'1000' ✓
A bacterial cell has a diameter of 3.2 µm. What is its diameter in nanometres?

32

320

3200 ✓

3 200 000
An nerve cell has a length of 3 mm. What is its length in nanometres?

$3 \times 10^{-6}$

$3 \times 10^{-3}$

$3 \times 10^{3}$

$3 \times 10^{6}$ ✓
A xylem vessel has a diameter of 62 µm, a bacterium cell has a diameter of 0.31 µm. How many times bigger is the xylem vessel than the bacterium?

0.005

5

20

200 ✓
Calculate the magnification of a red blood cell with a length of 7 µm in an image measuring 14 mm.

'2000x' ✓

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Most animals and plants are made up of millions or billions of cells.
Cell numbers can be expressed in standard form.
Cells are usually too small to see with the unaided eye.
Comparison of sizes of eukaryotic and prokaryotic cells, and cell structures, in µm, nm, and in metres in standard form.

Pupils commonly convert units incorrectly, multiplying when they should divide or dividing when they should multiply.

It can help to relate the unit conversions in the lesson to an everyday example, e.g. pounds to pence.

Million - 1 000 000, or one thousand thousand, or 10⁶.
Billion - 1 000 000 000 or one thousand million, or 10⁹.
Standard form - A way of writing down very large or very small numbers easily; e.g. 1000 = 10³.
Micrometre (µm) - One millionth of a metre, or 1 m / 1 000 000, or 1 × 10⁻⁶ m.
Magnification - Making small objects appear larger in order to see more detail.