Cell Membrane |
Prokaryotic and Eukaryotic Cells |
RNA's Role |
The Role of the Endoplasmic Reticulum and the Golgi Apparatus |
Energy Capture and Storage |
Macromolecules | What Determines the Eukaryotic Cell's Shape?
|What Determines the Eukaryotic Cell's Shape?|
|CA GR 9-12 Biology 1.j.|
A few Instructions back, you learned about prokaryotic and eukaryotic cells. You learned that eukaryotic cells are the cells that complex organisms (like us) are made of. And you learned that one of the main differences between the two kinds of cells is their structure. A eukaryotic cell always has a nucleus and organelles, while a prokaryotic cell doesn't.
We will now talk about what gives eukaryotic cells their shape, the
cytoskeleton. The cytoskeleton doesn’t just give these cells their
shape. It is also involved in cell movement.
We should probably remind you here that the three parts of a eukaryotic cell
are the membrane, the nucleus and the cytoplasm (the “cell fluid” in between the
membrane and the nucleus).
Three main fibers make up the cytoskeleton, those are:
We’ll tell you a little bit about each of them.
Remember actin and another protein called myosin, these filaments will come into play when we talk about muscle contraction in a later lesson.
These microtubules act as a scaffold to determine the cell’s shape and provide a set of “tracks” for cell organelles and vesicles to use inside the cytoplasm. They also help the flagella help the cell move (remember vesicles and flagella from previous Instructions?). The cilia and flagella are actually made up of these microtubules.
They also help with a kind of cell division called mitosis, which you’ll be learning more about in an upcoming instruction. They also help with a kind of cell division called mitosis, which we will discuss more in an upcoming instruction.
Intermediate Filaments The intermediate filaments are about 20nm in diameter and provide tensile strength for the cell. Tensile means stretching, so what these intermediate filaments do is help the cell stretch and contract. That's kind of like flexing the muscle in your arm to show how strong you are. These filaments are made up of fibrous proteins instead of globular like the other two fibers.
Experiments for Home and Classroom
This is fascinating, and ambitious, web site that invites students to
virtual tours of cells and all their structures -- including the
cytoskeleton and its component parts (with helpful worksheets for
guidance along the way). Tours are available in English, Spanish, French
and Russian. Start with the Instruction page. Note: this cell tour was
also suggested in a previous Instruction. Click:
To begin the tour, return to the home page at:
You have now completed Lesson 1 on Cell Biology and are ready to
do the Problem and Test sections.