1. Introduction to Cells

2. What Are Cells?
The smallest biological unit that can perform all life processes
Allows living things to obtain and use energy, respond to environment, and to reproduce.

3. Your Turn
Draw and describe what you think a typical cell looks like.

4. Scientists and cells… Robert Hooke (1665)
looked at a slice of cork (dead plant cells) under the microscope.
He saw “little boxes” which he named cells.
His microscope only magnified 30x

5. Scientists and cells… Anton van Leeuwenhoek (1675)
Discovered living single-celled organisms in pond water
Observed bacteri`a
His microscope magnified 270x

6. Scientists and cells… Matthias Schleiden (1838)
Concluded that cells make up every part of a plant

7. Scientists and cells… Theodor Schwann (1839)
Discovered that animals are also made up of cells

8. Scientists and cells… Rudolph Virchow (1858)
Proposed that cells come only from the division of existing cells

9. Your Turn
How can you remember what each scientist discovered?

10. The Cell Theory There are three parts to the cell theory:
All living things are composed of one or more cells.
Cells are the basic units of structure and function in an organism.
Cells come only from the reproduction of existing cells.

11. Cell Diversity
Not all cells are alike…in our own body we have over 200 different cell types.
They differ by…
size
shape
internal organization

12. Size: Cell size is limited by a cell’s surface area-to-volume ratio
All substances that enter or leave a cell must pass through the surface of the cell

13. Your Turn Why do you think cells are so small?
Why do you think cells have different shapes?

14. Shape: A cell’s shape reflects its function
Larger cells often have shapes that increase the surface area
These differences (size and shape) enable different cells to perform highly specific functions in the body
Examples:
Skin cells are broad and flat to cover the body.
Nerve cells have long extensions (can be 10,000x longer than they are thick) that allow it send and receive nerve impulses.

15. Shape:

16. Internal Organization Cell Structures That All Cells Have In Common…
Cell Membrane
Cell’s outer boundary that acts as a barrier between the outside environment and inside of the cell
Cytoplasm
Includes the fluid (cytosol) and almost all of the structures that are suspended in it inside the cell

17. Internal Organization Cell Structures That All Cells Have In Common…
Ribosome
Structure on which proteins are made
DNA
The genetic material containing instructions for making proteins, regulates cellular activities, and enables cells to reproduce

18. Your Turn
List the 4 things that all cells have in common

19. Types of Cells : Prokaryotes
Unicellular (made of only 1 cell)
Simple structure
No nucleus
No membrane bound organelles
Example: bacteria

20. Types of Cells: Eukaryotes
Can be unicellular or multicelled
Able to carry out more specialized functions than prokaryotic cells
DNA is stored in a nucleus
Have membrane-bound organelles
Example = plant and animal cells

21. Your Turn
Compare and contrast prokaryotic and eukaryotic cells

22. Types of Cells : Prokaryotes
Organism that is a single prokaryotic cell
UNICELLULAR
Genetic material is a single loop of DNA
Ribosomes, enzymes, & DNA are free floating in the cytoplasm
No nucleus or other membrane bound organelles
Surrounded by a cell wall (outside of cell membrane) that provides structure and support
1st appeared about 3.5 billion years ago
Very simple and small
Example = bacteria

23. Types of Cells: Eukaryotes
Organism that is made up of one or more eukaryotic cells
Some are single cells, others are multicellular
Able to carry out more specialized functions than prokaryotic cells
DNA is stored in a nucleus
Have a membrane, cytoplasm, ribosome, a nucleus, AND membrane-bound organelles
1st appeared 1.5 billion years ago
More complex and relatively large
Example = plant and animal cells