1. Unit 1: Cell Biology Section a: Cell Structure and Function
National 4/5 Biology
Unit 1: Cell Biology
Section a: Cell Structure and Function

2. We are learning to: Work out the size of cells using two calculations:
Total magnification
Conversion of millimetres to micrometres

3. Total Magnification Total magnification =
magnification of x magnification of
objective lens eye piece
Example
- if eyepiece has a magnification of x5 and objective lens has magnification of x40. Total magnification is 200x
(5 x 40)

4. Total magnification calculations
Calculate the total magnification for the following:
Eyepiece is 5x and objective lens is 25x
Eyepiece is 5x and objective lens is 50x
Eyepiece is 5x and objective lens is 250x

5. Cell size 1 millimetre (mm) = 1000 micrometres (um)
Therefore a field of view of 2mm diameter = 2000 micrometres
So if 10 cells are going across the diameter
each cell will be 200 micrometres (2000/10 = 200)

6. Calculations How wide are the cells in micrometres? 2mm = 2000um
3 cells across field of view
2000/3 = um

7. Calculations 2 How long are the onions cells in micrometres?
5mm
5mm = 5000um
5 cells across the field of view
5000/5 = 1000um

8. Calculations 3
The following slide has been magnified 100x. How long is one cell?
5mm = 5000um
5 cells in field of view
5000/5 = 1000um
1000/100 = 10um

9. Your turn!
In pairs come up with two examples for your class mates to work out
Remember you are the teacher you have to know the answer
If you want to make it more difficult show the working with an error that they have to spot!

10. For fun Using plasticine Build models of a plant or animal cell
Label the structures and state their functions
Extra:
State how the cell you have chosen is similar or different to the three other types of cell you have studied