Cell Structure

Plasma Membrane:

• Structure:

1. Single Membrane, phosopholipid bilayer
2. Integrated transported and receptor proteins

• Function:

1. Selective permeability allows osmosis and diffusion for small molecules and ions and keeps cell stability and structure
2. The integrated proteins allow the transportation of impermeable molecules and allow the cell to live.

Cell Wall:

• Structure:

1. Carbohydrate fibers that are held together by hydrogen bonds and polypeptide bonds that create a strong wall

• Function:

1. Protection of the cell and structural support in the plant, e.g. wood

Cytoskeleton:
The cytoskeleton system of the cell is a complex organization of dense fibers, actin filament, intermediate filament, and microtubules. These fibers help give structural support for the cell by keeping the cell a certain size and holding the nucleus and organelles in their designated areas. The system also moves the cell itself, the actin filament, and move objects in the cell.

Actin Filament:

• Strucuture:

1. Fibrous material of globular protein, actin
2. Double helix
3. Myosim

• Function:

1. Maintain cell shape by resisting tension, similar to steel rods in concrete
2. Creates the ability to have both cellular and inner cell movement by rotating
3. Myosin is the motor protein which is key in the transformation of ATP into mechanical energy which causes the actin to "slide"
4. The combination of Myosin and actin filament create 3 important jobs in the cell: cellular movement (actin acts as a muscle and causes contractions and other motions that create a 3 step process from motion), cell division (actin filament pinches the plasma membrane), and cytoplasmic streams in long or large cells in which diffusion will take to long.

Intermediate Filaments:

• Structure:

1. Defined by shape, not material, but are fibers configured into a large cable

• Function:

1. This filament acts purely as a beam which holds the cell in it's particular shape and helps keep the nucleus and other organelles in their assigned locations.

Microtubules:

• Structure:

1. a hollow tube of helices of a-Tubulin adn b-Tubulin dimer
2. kinesin
3. Centrosome
4. Centriole

• Function:

1. The microtubules act just like the actin filament, however the microtubules are larger in diameter. They give support to the cell and allow for movement of molecules and nutrients.
2. The kinesin is the motor protein in microtubules that moves objects around. But unlike myosin, kinesin moves when the ATP is added and the protein creates the mechanical energy by "walking" up and down the microtubules.
3. This is the center for which microtubules are created and grow from this region.
4. Still have an unknown reason.

• Microtubules also help in cell division by forming cell plates during plant cell division and form the new cell wall. They also move chromosomes during division, along with organelles.