What We Cannot See

Cells and Microscopes - More about these things in the subs ⬆

Quiz - microscopes and cells

Units and Lengths

Above is a chart of important sizes / lengths

Common units that we often use are millimetre, centimetre, metre and kilometres.

Micrometre and nanometre are often used when talking about microscopes and cells.

Useful Things

• The smallest object seen with the naked eye is 0.1 mm
• The smallest object seen with a light microscope is 0.2 μm
• The smallest object seen with an electron microscope is 0.1 nm

• 1 um = 1000 nm
• 1 um = 0.001 mm
• 1 mm = 1000 um
• 1 um = 1,000,000,000 km
• 1 m = 1000000 um
• 1 km = 1000 m
• 1 um = 0.000001 m
• 1 km = 1,000,000 mm
• 1 mm = 0.000001 km

Cells

An overview of Cells: textbook pg. 40-44 Science Quest 8, click here for the link

Good questions to do: pg. 44 1-2

Microscopes

• The smallest object seen with the naked eye is 0.1mm
• The smallest object seen with a light microscope is 0.2μm
• The smallest object seen with an electron microscope is 0.1nm

Microbes

Microbes can only be seen when using a powerful microscope because they are so small. There are 3 types of microbes: 

• Fungi
• Bacteria 
• Virus

Some microbes can cause disease and are often called germs but most microbes are very useful.

Fungi: 

• Can be single cells, often found joined together as a long chain
• Feed on dead and decaying plants and animals
• Example: Mould on stale bread
• Click here for a comic on The Rise of Yeast Cells
• Below is a picture of a yeast cell.

Bacteria:

• Single cells, lots of different shapes, rod shaped, round or spiral
• Take in food from where they are living. Some make harmful wastes
• Example: Bacteria in gut break down food
• Below is a picture of a bacterium (bacteria cell)

Virus:

• Single cells
• Do not feed or breathe. Can only live inside another living cell
• Example: Flu virus
• Below is a picture of virus cells