Cell Theory

The Cell Theory A Timeline

Late 1500’s

• Hans and Zacharias Janssen

• Dutch lens grinders, father and son • produced first compound microscope (2 lenses)

Late 1500’s

Robert Hooke ( 1665)

• Used light microscope to look at thin slices of plant tissues -- cork

• Looked empty, like monk’s chamber

• Called tiny chambers

“cells”

• Looked at pond water organisms

• First to see living microscopic organisms.

• Made careful sketches.

Anton von Leeuwenhoek (1673)

Matthias Schleiden -- 1838

• German Botanist (studied plants)

• Viewed plant parts under a microscope

• Discovered that plant parts are made of cells

• He concluded:

“All plants are

made of cells.”

Theodore Schwann -- 1839

• German scientist who studied animals - zoologist

• Saw that all animals he studied were cellular so concluded:

“All animals are made of cells.”

Rudolf Virchow - 1855• German physician

who studied cell reproduction

• “Where a cell exists, there must have been a preexisting cell.”

The Cell Theory• All living things are composed of one

or more cells.

• The cell is the basic unit of life in all living things.

• New cells are produced from existing cells.

Cell Similarities• Cells come in many shapes and sizes with different

duties but …• All are surrounded with a cell membrane• All cells have hereditary material (DNA)• All have cytoplasm and organelles. Cytoplasm

is the fluid within a cell which provides a safe environment for the organelles. Organelles are the structures within the cell that have specific duties to make the cell a functioning unit.

Two Types of Cells• Eukaryotic

• Are complex and of different types.

• Have a nucleus and many organelles.

• Contain more DNA due to different jobs within the cell. DNA is linear (in a line).

• Possess a cell membrane or a cell wall.

• All living things other than bacteria.

Two Types of Cells• Prokaryotic

• Contain no nucleus.• Have no membrane

covered organelles, but do have ribosomes to make protein.

• Possess circular DNA.

• Are bacteria.