1. 4.1 Cell Theory
Biology, I

2. Cells
Cells: smallest unit of matter that can carry on all of the processes of life

3. Cells
The Cell Theory: developed by theories of Hooke, Schleiden, Schwann, and Virchow
Every living organism consists of one or more cells
The cell is the structural and functional unit of all organisms. A cell is the smallest unit of life.
All living cells come from pre-existing cells
Cells contain hereditary material, which they pass to their offspring

4. Cells
With better microscopes, scientists observed that some cells contained specialized structures
Organelles: cell parts that perform a specific job or function for the cell
Found in eukaryotic cells such as plant and animal cells

5. Cells 1. Nucleus 2. Ribosomes 3. DNA 4. Cell membrane 5. Organelles
Two Cell Types
Eukaryotic cells: cells with a membrane-bound nucleus and organelles
Ex: plant and animal cell
1. Nucleus
2. Ribosomes
3. DNA
4. Cell membrane
5. Organelles
6. Cytoplasm

6. Cells 2. DNA 3. Cell membrane 1. Ribosomes 4. Cell wall 5. Cytoplasm
Two Cell Types
Prokaryotic cells: cells with no membrane-bound nucleus or organelles (except ribosomes)
Ex: bacteria
2. DNA
3. Cell membrane
1. Ribosomes
4. Cell wall
5. Cytoplasm

7. Cells – The Inner life of a Cell
Left: Colorized micrograph of a prokaryotic cell of the bacterium.
Right: Colorized micrograph of a eukaryotic cell of the green algae.

8. Contrasting (Differences) between cells
Cell Type
Nucleus?
Membrane-bound Organelles?
Unicellular or Multicellular?
Prokaryotic: No
Unicellular
Eukaryotic:
Yes
Multicellular

9. Structures found in all cells
Despite being so different, prokaryotic & eukaryotic cells have some structures in common:
BOTH Prokaryotic and Eukaryotic cells contain:
Cell membrane
Cytoplasm
DNA
Ribosomes

10. How big is too big? Constraints on cell size
Why are cells so small?
They are limited by how quickly the cell can gain materials
Rate at which materials are exchanged depends on the size of the cell membrane (surface area of the cell)
Rate at which materials are used (oxygen, water) or produced (waste) depends on the volume of the cytoplasm
The cell can’t use materials faster than it can get them 

11. How big is too big? Constraints on cell size
What happens to the surface area & volume as a cell gets bigger?
The volume gets larger quicker than the surface area
The cell USES materials faster than it can get them
Cell DIES

12. Ideal cell size? What is the ideal cell size?
Small
Cells should have a large surface area-to- volume ratio