Introduction to the Cell

1. All living things are composed of 1 or more cells.

2. In organisms, cells are the basic unit of structure & function

3. Cells are produced only from existing cells.

MICROSCOPES

1. Light Microscope

2. Electron Microscope (1950’s)

• Transmission Electron Microscope

• Scanning Electron Microscope

Light Microscope

• works by passing visible light through a thin section of specimen and then through glass lenses

• resolving power = 0.2 µm (size of small bacteria)

• magnification about 1000x

Advantages of using Light Microscope:1. Color image instead of monochrome

2. Larger field of view

3. Easily prepared sample material

4. Possible to observe living material & observe

movement

Electron Microscope (1950’s)

• uses electron beams

which have shorter

wavelengths of light

• resolving power = 0.2

nm (most cell

structures)

• magnification up to

40,000x

Advantages

Electron Microscope1. Transmission Electron Microscope – electrons transmitted through

specimen are focused and image is magnified using electromagnets

– used to study internal cell structure

2. Scanning Electron Microscope – electron beam scans the surface

of a spec.– useful for studying the surface of

specimen in 3-D.

PINHEAD

Moth wing scales; Madagascan moon moth, Argema mittrei

Disadvantages to EM…

• can only view dead cells (elaborate preparation)

• very expensive

zooxanthellae cells cultured from coral

Aiptasia pulchella in a Scanning Electron

Microscope

WE CAN ALSO STUDY CELLS BY...

• Cell Fractionation = disrupting cells to separate out cell organelles

• Centrifugation = spinning mixtures of cells and their parts at very high speeds; separates the components