Opening Questions
• Do you think the organelles that are found in the cell move around the cell or stay in one place in the cell?
• If you think they move…how do they?

Learning Outcomes
• Tell what molecules make up the cytoplasm.
• List the important parts of the cell that are found in the cytoplasm.
• Distinguish between cytoskeleton proteins and motor proteins.
• Discuss why the cytoplasm is a major part of every cell.

A.


The cytoplasm is found between the plasma
(cell) membrane and the nucleus

It is MADE UP of organic substances and water.






1. C YTOSKELETON

The cytoskeleton
MADE UP OF protein filaments, motor proteins, and microtubules


These fibers extend from the nucleus to the cell(plasma) membrane

Gives shape and allows the cell and organelles to move.

Cytoskeleton

1. Microtubules

2. Protein Filaments

A. Intermediate

B. Actin

3. MotorProteins

A.

B.

C.

2. Tubules of the
Cytoskeleton
 a. microtubules
 b. intermediate filaments
 c. actin filaments

B and C are PROTEIN
FILAMENTS

A . M ICROTUBULES

Microtubules are small hollow cylinders composed of 13 chains of proteins.

Their assembly is controlled by a structure called a centrosome.


The centrosome is a structure that is found very near the nucleus.

Microtubules are said to radiate out from the centrosome.


This pattern of microtubules helps to maintain a cell’s shape.

It also serves as a track system (like train tracks) in which organelles and materials move throughout the cell.


A centriole is a structure that comes in pairs and is said to work closely with the centrosome.

The centrioles in the cell play a very important role in cell division (discuss later in the year)

B . I NTERMEDIATE
F ILAMENTS

They are called intermediate because they are medium in size.
(between microtubules and actin filaments)

They are rope like chains of proteins.


The intermediate filaments are found mainly between the nuclear envelope (membrane) and the plasma (cell) membrane.


The proteins that make up these filaments are unique to the cell they are found in.

Example

Intermediate fibers made up of keratin give strength to skin cells.

C . A CTIN F ILAMENTS

Actin filaments are long filaments.

They are the largest of the three filaments

They are said to be made up of a globular protein.


These proteins tend to twist around each other in a helical manner.

The actin filaments form a complex web just under the plasma(cell) membrane.


The web supports the cell and projections that may come of the membrane.

3. Major Motor Proteins of the Cytoskeleton
• a. myosin
• b. kinesin
• c. dynein

Help move organelles around the cell.
Help move materials in and out of cell.

• Myosin works hand and hand with the actin filaments to help with movement in the cell.
• They are helpful when the cell engulfs a large molecule.
• (pinocytosis or phagocytosis)

• Myosin hand the actin filaments also are used by the cell to pinch the original cell into two new cells during cell division.

A process known as cytokinesis.

• Myosin is also used by muscles cells
• When muscles contract, myosin pulls actin filaments to the middle of the cell

• Finally kinesin and dynein are motor proteins that help move organelles around the cell…
• They attach to the organelle..unattach and then reattach to the organelle further down a microtubule.

• They also perform the same way when moving material to and from the Golgi Apparatus

• 1. Helps give cell its shape.
• 2. Moves things for the cell.
• 3. Holds organelles.

• The cytoplasm is ONE of the
THREE major parts of the cell.
• It is made up of organic molecules (motor proteins/microtubules) and water
• Found floating and moving around it are organelles

• Protein filaments and Motor
Proteins together in the cytoplasm to give the cell shape and move organelles and materials around the cell.

• These are the main reasons that the cytoplasm is considered ONE of the
THREE major parts of every cell.