| Relative size of micro-organisms. nanometre = 10-9 m | |
| 
 
 Medium sized molecule is of the order of 1 nanometer |  | 
| Cell membrane is about 10 nanometres thick |  | 
| Virus -smallest known reproducing organism. Size is of the order of 10-100 nanometres. |  | 
| Bacteria are bigger than viruses at about 1,000 to 3,000 nanometres. Bacteria are shown sitting on the point of a pin. |  | 
| The picture on the right shows viral particles infecting a bacterium. |  | 
| Relative size of white blood cell and bacteria (red) |  | 
| Red blood cell is about 10,000 nanometres wide. |  | 
| If a red blood cell was 1 metre wide how big would the following be relative to the red blood cell? A bacterium 3,000 nanometres long. | |
| A virus particle 100 nanomtres long | |
| A cell membrane 10 nanometres thick will be | |