How are cells classified?
There are two categories of cells.  One is called the Prokaryote ( "pro" rhymes with "low") which is a very primitive "lower" form of cell.  This would include all cells that do not have membrane bound organelles such as those in bacteria.  Eukaryotes are more advanced in that they have a nucleus and other membrane bound organelles.  .
Let's Start at the beginning...click on the triangle!!

Plant cells are different from animal cells in that they:
....have rigid cell walls.
....have chloroplasts.
....have a single large water vacuole.
Plant cells have a cleavage plate when they divide whereas animal cells have a cleavage furrow.  Click on the plant cell and virtually microdissect a plant cell.
Welcome to the Zone...click here to learn all there is to know about cells and their parts. Take the virtual tour!!
Got a question about cells? Click on the "?" send it to the teacher!!
The cell membrane is more than just the boundary of the cell. It regulates the passage of materials into and out of the cell.  Click on the molecule to the left to learn more about this organelle.
Discover how genetic information is stored in your cells.  This information is the reasons cells with different functions look different and behave differently.  Learn all about mitosis, or cell division by clicking on the gene at left.  Mitosis is cell division resulting in two identical daughter cells.  It has five stages: interphase, prophase, metaphase, anaphase, and telophase.
Now that you have studied all about the cell, see if you can answer the following questions.  Thinking caps on....lets go!
1.  Why are there so many small cells in an organism instead of a single large cell?

2.  What tells a cell it is time to divide?

3.  Why don't animal cells need the rigid cell wall that plants cells have?

4.  What role does cytoplasm play in maintaining homeostasis in the cell.

5.  Name the organelle that has earned the following nickname:

powerhouse

suicide sac

"9 + 2"

6.  What is the role of cyclosis or streaming within a cell?

7.  What is the largest single cell from an animal in the world?

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3, 2002

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Keeping in balance with its environment: OSMOSIS
When a cell is put into an environment where there is more salt on the outside of the cell than on the inside, water begins to move into the cell to try and get the concentration diluted so that it is the same inside as out (ISOTONIC).  This condition when there is too much salt inside is called HYPOTONICITY, and when there is too much salt outside, it is called Hypertonicity.  If the salt concentration is so high inside that so much water  comes in that  it bursts, this is called PLASMOPTYSIS.  (study hint: pop rhymes with mop in plasmoptysis!)  When there is so much salt outside of the cell that all the water leaves the cell to dilute it, this cell shrinkage is called PLASMOLYSIS.  This balance of water is very important to the cell...in plant cells there has to be enough water in the cell to maintain pressure on its rigid cell wall.  Plants wilt or go limp when there is not enough water left in the cell to do this.  Celery gets crisp once wilted if you cut off the bottom and put it in water. Why?  Because the water goes back into the cell and restores the pressure on the wall. If salmon lay there eggs in fresh water when they are supposed to be laid in salt water, what do you thing will happen? What do you think would happen if human blood cells which are normally in a salty solution were put into distilled water?  This balance of solute and solvent is very important to living cells.
Time to test yourself
Click on the professor to see how many questions you can answer correctly!