CHAPTER 3 CELLS3.1 Cell Theory

KEY CONCEPT Cells are the Basic unit of life.

Discovery of Cells

• The cell theory grew out of the work of many scientists and improvements in the microscope.

• A cell is the smallest unit capable of carrying out life functions

• More was learned about cells as microscopes improved.

• The cell theory is a concept of biology.

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

Wacky theory of cell history• Cell Theory

Discovery of Cells

• Zacharias Jannsen

• Man who invented the compound microscope

Discovery of Cells

• Robert Hooke• In 1665 he used a

microscope to look at a thin slice of cork

• Responsible for naming cells after looking at cork

• Named them after the chambers that monks lived in

Discovery of Cells

• Anton van Leeuwenhoek

• In 1674, first scientist to observe and describe living cells from looking at pond water

• Called them

Animalcules

The Cell Theory

• Matthias Schleiden• German Scientist• 1838, concluded all

plants are made of cells• Cofounded the Cell

Theory

The Cell Theory

• Theodore Schwann• German Zoologist • 1839, concluded all

animals were made of cells

• Cofounder of cell theory

The Cell Theory

• Rudolph Virchow• German Scientist• 1855, concluded all cells

come from other cells• Cell Division

Cell Theory

• 3 major principles of the Cell Theory1. All organisms are

made of cells

2. All existing cells are produced from other living cells

3. The cell is the most basic unit of life

• There are two types of cells: Prokaryote and Eukaryote• All cells share certain characteristics.

• Cells tend to be microscopic.• All cells are enclosed by a membrane which regulates the flow of

materials into and out of the cell.• All cells are filled with cytoplasm – a jelly like

substance containing dissolved molecules

like proteins and minerals.

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

There are two types of Cells: Prokaryotes and Eukaryotes• Prokaryotes

• Do not have a nucleus.• DNA in cytoplasm• Do not have membrane-bound

organelles• Single celled organisms• Less complex

Ex Bacteria

cell membrane

cytoplasm

There are two types of Cells: Prokaryotes and Eukaryotes• Eukaryotes

• Have a nucleus.• DNA in nucleus• Eukaryotic cells have

membrane-bound organelles.• Single or Multicellular• More complex and

Specialized Ex. Most plant and

animal cells

nucleus

cell membrane

organelles