Write everything that is BLACK Section 3-1 “Cells” Write everything that is BLACK

KEY CONCEPT: Cells are the Basic unit of life.

Many scientists contributed to the cell theory. The cell theory grew out of the work of many scientists and improvements in the microscope. Many scientists contributed to the cell theory.

The Cell Theory: 1. All organisms are made of cells

2. All existing cells are produced by other living cells

3. The cell is the most basic unit of life

All cells share certain characteristics: Cells tend to be microscopic. All cells are enclosed by a membrane. All cells are filled with cytoplasm. cell membrane Bacterium (colored SEM; magnification 8800x) cytoplasm

There are two cell types: 1. Eukaryotic cells: Have a nucleus Have membrane- bound organelles Usually multi-cellular Example: plants, animals nucleus organelles cell membrane

2. Prokaryotic cells: Do not have a nucleus Do not have membrane-bound organelles Usually single-celled Example: bacteria cell membrane cytoplasm