AQA GCSE Scale and Size of cells (Biology)
Scale and size of cells
Most Scientists use units of micrometers (μm) when measuring cells.
The following are in order of size, smallest on the left, largest on the right.
Converting units
You can use the diagram below to help you to convert the units
These are all compared against 1 meter.
In the case of “centi”, 1 meter = 100cm.
A centi is 10-2 of a meter, or 0.01 of a meter. This means that 1/100th of a meter is a centimeter. We already know this because 1 m = 100cm.
| Name of Prefix | Symbol | Scientific notation | Value |
|---|---|---|---|
| centi | c | 10-2 | 0.01 |
| milli | m | 10-3 | 0.001 |
| micro | μ | 10-6 | 0.000001 |
| nano | n | 10-9 | 0.000000001 |
Standard form
Standard form is a way of writing very large numbers or very small numbers in an easier format.
In biology we often use it for writing very small numbers.
Using Standard form to write large numbers
If we need to write 1 million, this would be 1,000,000 as a number.
When written in standard form it will be 1 x 106. The 6 means that the decimal point has moved 6 places to the left!
Using Standard form to write very small numbers.
If we need to write 0.000001 in standard form, we need to move the decimal place 6 places to the right.
Orders of Magnitude
Order of magnitude refers to the scale or size of a value in powers of ten.
If one value is 10 times bigger than another → it’s 1 order of magnitude larger
If it’s 100 times bigger → 2 orders of magnitude larger
If it’s 1,000 times bigger → 3 orders of magnitude larger, and so on
If a covid virus is 0.1μm, and an animal cell is 10μm. Then the animal cell is 100 times larger than the covid virus. This means that the animal cell is 2 orders of magnitude larger than the covid virus.
Practice Question
1.State the approx size in μm of an animal cell
2.A cell has a size of 100μm. Convert the 100μm into cm.
3. Write these numbers in standard form
3a. 120,0000
3b. 0.00000016
4. A plant cell has a size of 100μm, whilst a bacterial cell has a size of 1μm. How many orders of magnitude larger is the plant cell compared to the bacterial cell.