New
New
Year 10
Edexcel
Higher

# The size and scale of cells: including standard form

You can describe numbers and sizes of cells using appropriate units and standard form.

New
New
Year 10
Edexcel
Higher

# The size and scale of cells: including standard form

You can describe numbers and sizes of cells using appropriate units and standard form.

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## Lesson details

### Key learning points

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

### Common misconception

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.

### Keywords

• Million - 1,000,000, or one thousand thousand, or 10⁶.

• Billion - 1,000,000,000,000 or one million million, or 10¹².

• 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.

Video clips that show the size and scale from an atom to the whole universe can help pupils to understand the relationships and numbers involved.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
In which type of cell is the genetic material not enclosed within a membrane-bound nucleus?
eukaryotic cell
Q2.
Which piece of apparatus is used in science laboratories to view cells?
telescope
hand lens
magnifying glass
Q3.
In microscopy, what does the term magnification mean?
Correct answer: 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
Q4.
What is being described: "the distance at which two distinct points of a specimen can still be seen"?
magnification
brightness
microscopy
Q5.
On which part of a microscope is the specimen placed in order to view it?
Q6.
What is the purpose of the objective lenses on a light microscope?
to control the amount of light
to hold the microscope slide
to provide structural support

## Exit quiz

### 6 Questions

Q1.
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)
Q2.
How many nanometres are in a micrometre?
Correct Answer: 1000, one thousand, thousand
Q3.
A bacterial cell has a diameter of 3.2 µm. What is its diameter in nanometres?
32
320
3 200 000
Q4.
An nerve cell has a length of 3 mm. What is its length in nanometres?
$$3 \times 10^{-6}$$
$$3 \times 10^{-3}$$
$$3 \times 10^{3}$$
Correct answer: $$3 \times 10^{6}$$
Q5.
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