Chapter 4: A Tour of the Cell

 Introduction to the microscope:  The importance of the invention.  "Seeing is Believing."

The microscope played a significant role in realization that living things were made up of cells. 

This realization lead to the Cell Theory:

1) All living things are made of one or more cells,
2) Cells come from pre-existing cells,
3) Nothing less than a cell can show the properties of life.

In 1665 Robert Hook used an early microscope to look at a thin slice of cork, the dead cells of oak bark. What he saw looked like rooms, which he called cells.  The microscope was developed from eyeglass markers ideas in the late 1500 who realized that using several glass lenses magnified things.

The Light Microscope allows light to pass through a specimen and uses two lenses to form an image.  Light waves are scattered as they pass through material.  Therefore light microscopes can magnify up to about 1000t times.

Electron Microscopes use beams of electrons focused my magnetic fields. These offer higher resolutions than light microscope.  These are used to only examine non-living cells and tissues.  The samples are chemically preserved so that they can be examined in a vacuum. The electrons are placed in a vacuum to prevent them from being scattered.

Electron Microscopes: How They Work