Discovering Cells

Pages 50-57

Cells are the basic unit of structure and function in all living things.

• All living things are made of cells• All life processes happen in cells– Getting oxygen, getting rid of waste, obtaining

food, growing, etc.

• Cells are small, can’t be seen with the eye.

First Observations of Cells• 1590-The invention of the

microscope by Hans Janssen.• This invention makes it

possible for people to discover and learn about cells

• In class we use a COMPOUND LIGHT MICROSCOPE – this is a scope with more than one lens that uses light to focus

Robert Hooke• English scientist and English scientist and inventorinventor

• One of the first people to observe cells

• 1663 he observed the cells of a slice of cork through a compound microscope he built himself

• Hooke called them cells because they reminded him of tiny rectangular rooms

Anton van Leeuwenhoek• Amateur scientist who

made his own lenses and constructed simple microscopes

• First person to spot tiny single-celled organisms that we call bacteria. He first noticed these organisms on teeth scrapings.

• Called them animacules.

Once cells were seen, the cell theory was developed.• Shleiden and Schwann’s observations that all plants

were made of cells and all animals were made of cells led to:

“All living things are made of cells.”• Virchow proposed that new cells are formed ONLY

from cells that already exist. This led to:“All cells come from cells.”

• As more cells were viewed using microscopes, it became believed that:

“Cells are the basic unit of structure and function in all living things.”

Advancements in Microscopy• Scanning Electron

Microscopes (SEM)– Use a beam of electron

INSTEAD of light to produce a magnified image.

– The resolution of SEM is MUCH BETTER than that of a light microscope

– Can magnify a specimen up to 150,000 times its size.