1. The Characteristics of CELLS
Mod.A. U.1 L.1

2. What is a Cell? The smallest functional and structural unit of all
living organisms
All organisms are made up of cells.
An organism is any living thing.
“Cells” named by Robert Hooke

3. The Cell Theory Contributed to by various scientists:
Robert Hooke – In 1663 he observed a slice of cork under his microscope and called the compartments “cells” for the first time.

4. Anton van Leeuwenhoek – (1673) He looked at pond water under his microscope, and observed microscopic organisms, which he called “animalcules” meaning little animals- including bacteria.
Matthias Schleiden - (1838)
He observed plants, and concluded that all plants were made up of cells.

5. Theodor Schwann – In 1839, he similarly concluded that all animals were made up of cells.
5. Rudolf Virchow – In 1855, Virchow proposed that new cells formed only from existing cells.

6. The Cell Theory - states that:
All organisms are made up of one or more cells
The cell is the basic unit of (structure and function) life
All cells come from existing cells

7. Parts Common to ALL Cells
Cell Membrane –
Cytoplasm –
Organelles –
DNA –

8. Two Types of Cells: Compare
PROKARYOTIC EUKARYOTIC

9. Do not have a nucleus Have a nucleus Prokaryotic e.g. bacteria
Smallest and oldest cells
Do not have a nucleus
DNA is one long circular chain
No membrane-covered organelles
Have only ribosomes (no organelles)
Have a cell membrane and hard outer cell wall
Eukaryotic
e.g. all other cells of plants, animals, fungi, etc
Larger sizes and are more complex
Have a nucleus
Has more and linear DNA strands
Has membrane covered organelles
All have cell membranes, some have cell walls

10. Why are most cells small . . . ?
Size is limited by outer surface area
Take in food, pass out waste over whole surface area
As cells grow volume increases faster than surface area
Surface area not enough Cell too large
Calculate Surface area-to-Volume ratio
Smaller cells have larger S.A:Vol. ratio 
Larger cells have smaller S.A.:Vol. ratio 
1:1, 4:8 or 1:2, 9:27 or 1:3, 16:64 or 1:4