2. So, What IS a Cell?
A cell is the basic unit of structure and function in all living things.
It needs water and nutrients to survive.
It is found in all living things: bacteria, plants, and animals.
It is NOT found in non-living things.

3. Which ones would have cells?

4. Which ones would have cells?

5. How Cells Were Discovered…
1665 Robert Hooke: Looked at a slice of cork through a microscope and discovered tiny boxes which he called “cells.”

6. How Cells Were Discovered…
1673 Anton von Leeuwenhoek: looked at pond scum through a microscope and discovered single-celled organisms called protists.
Amoeba, an example of a protist

7. How Cells Were Discovered…
1838 Matthias Schleiden: studied plants and concluded that all plant parts were made of cells.
Tomatoes:

8. How Cells Were Discovered…
1839
Theodor Schwann:
studied animals and concluded that all animal tissues are made of cells.
Pueblan Milk snake
Clown fish
Grizzly bear

9. How Cells Were Discovered…
1858 Rudolf Virchow: discovered that cells could only come from other cells.

10. ABC’s of the “Cell Theory”
With all these discoveries, Schwann and Virchow came up with the cell theory:
All organisms are made of cells
The cell is the Basic unit of all living things
All cells Come from existing cells
1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

11. How Big are Cells?
Most cells are so tiny that you have to use a microscope to see them.
1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

12. Why are cells so tiny? Because of the surface area-to-volume ratio:
Cells take in nutrients and get rid of wastes through their outside surface.
BUT the volume (space inside) grows faster than the surface area (the cell’s surface).
1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

13. Why are cells so tiny?
If the volume becomes too big, the cell cannot survive because….
it can’t get enough nutrients in &
can’t get rid of wastes fast enough.
Therefore, a cell only grows to a certain size.
1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

14. Balloon Analogy for Cell Size
If you blow into a balloon, the volume increases.
Eventually, the balloon’s surface
cannot stretch anymore.
When this happens, the balloon
cannot continue to exist and will pop.
Likewise, if a cell’s volume increases too much, the cell’s surface will not be able to get nutrients in or wastes out fast enough and it will die.

15. A few cells are big
Some cells are big because they don’t need to take in nutrients or get rid of wastes.
Ie. Chicken egg is a cell
1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

16. Prokaryotes 1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

17. Eukaryotes 1 & 2: building block/legos
3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

18. Prokaryotic Cell (Prokaryote)
Eukaryotic Cell (Eukaryotes)
No nucleus
2 types: bacteria &
archebacteria
Smallest cells
Organelles:
DNA & ribosomes
only
Use flagellum (tail)
to move
Most prokaryotes are
Unicellular (only 1 cell)
Have a nucleus
Examples:plants, animals, and humans
Largest cells (10x larger than bacteria cells!)
DNA in nucleus
Many organelles
Most eukaryotes are multi-cellular (made of more than 1 cell)
*DNA
ribosomes, * cell membranes
cytoplasm