Summary AQA GCSE Biology Chapter B1 - Cell Structure and Transport

The World of the
Microscope
 Living things are made of cells
 Some of these cells are so small that you can only see them under a microscope




The Light Microscope
Developed Mid-17th century (continue to develop to present day)
Use To look at cells / Use sees both dead and alive specimens
Process Uses a beam of light to form an image of an object (SIMPLE TO USE)
Magnification Best can magnify around x2000, school microscopes can only magnify x700. Can
magnify live species
Price Relatively cheap
Mobility Can be used almost anywhere

, The Electron Microscope
Developed In the 1930s
Use Allows biologists to see and understand the subcellular structures inside a cell / Use can
only be used to see
Process Uses a beam of electrons to form an image
Magnification Can magnify up to x2,000,000. Transmission electron microscopes give 2D images
with  high magnification + resolution  Scanning electron microscope gives dramatic 3D
images with  lower magnification
Price Very expensive
Mobility Very large. Have to be kept in special temperature, pressure and humidity-controlled
rooms.


Calculating Magnification

Magnification of eyepiece lens x Magnification of objective lens
Example


If your




eyepiece lens is x4 and your objective lens is x10
The overall magnification is:
When labelling drawings
made using a microscope, 4 x 10 = x40
make it clear that the
magnification you give is the
magnification at which you
looked at the specimen.

, Magnifying & Resolving Power
Resolution – The ability to distinguish between two separate points


Resolving Power – The resolving power of a microscope
affects how much it can show.
The Resolving power of a:
- Light microscope is 200nm
- Scanning Electron microscope is 10nm
- Transmission Electron microscope is 0.2nm




Animal & Plants Cells
Animal Cells