Cell+Wall+and+Cell+Membrane

= __Cell Wall and Cell__ __Membranes__  = =   = __//**Cell Wall**//__ __//**Cell Membrane**//__ >         
 * Function- Provides a protected framework for a plant cell to survive. Also allows plants to grow to great heights. It is the skeleton of a cell.
 * Structure- Cell Walls are made of a specialized carbohydrate **Cellulose**, which is a complex sugar. Contains **plasmodesmata**, small holes in the cell wall that allows nutrients, waste, and ions to pass freely into the cell.
 * Cell walls that contain cellulose are found in plant cells only. Bacteria, fungi, and protozoa all contain cell walls but are not made of the same substance.
 * Plant cells have a rigid, protective cell wall made up of polysaccharides. In higher plant cells, that polysaccharide is usually cellulose. The cell wall provides and maintains the shape of these cells and serves as a protective barrier. Fluid collects in the plant cell vacuole and pushes out against the cell wall. This turgor pressure is responsible for the crispness of fresh vegetables.
 * Function- Keeps all of the components of the cell inside.
 * Structure- Compounds called **proteins** and **phospholipids** make up most of the cell membrane. Scientists describe the organization of the phospholipids and proteins with the **fluid mosaic model**. That model shows that the phospholipids are in a shape like a head and a tail. The heads like water (**hydrophilic**) and the tails do not like water (**hydrophobic**). The tails bump up against each other and the heads are out facing the watery area surrounding the cell. The two layers of cells are called the bilayer.
 * Cell Membrane : Every cell is enclosed in a membrane, a double layer of phospholipids (lipid bilayer). The exposed heads of the bilayer are "hydrophilic" (water loving), meaning that they are compatible with water both within the cytosol and outside of the cell. However, the hidden tails of the phosopholipids are "hydrophobic" (water fearing), so the cell membrane acts as a protective barrier to the uncontrolled flow of water. The membrane is made more complex by the presence of numerous proteins that are crucial to cell activity. These proteins include receptors for odors, tastes and hormones, as well as pores responsible for the controlled entry and exit of ions like sodium (Na+) potassium (K+), calcium (Ca++) and chloride (Cl-).
 * The cell membrane (or __plasma membrane__) surrounds all living cells, and is the cell's most important organelle. It controls how substances can move in and out of the cell and is responsible for many other properties of the cell as well. The membranes that surround the nucleus and other organelles are almost identical to the cell membrane. Membranes are composed of phospholipids, proteins and carbohydrates arranged in a __fluid mosaic structure__, as shown in this diagram. (See Below)
 * **The proteins**  usually span from one side of the phospholipid bilayer to the other (__integral proteins__), but can also sit on one of the surfaces (__peripheral proteins__).
 *  Proteins that span the membrane are usually involved in transporting substances across the membrane
 * Proteins on the inside surface of cell membranes are often attached to the cytoskeleton and are involved in maintaining the cell's shape, or in cell motility.
 * Proteins on the outside surface of cell membranes can act as __receptors__ by having a specific binding site where hormones or other chemicals can bind.
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Movement Across Cell Membranes- Five Methods
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Lipid Diffusion
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Osmosis
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Passive Transport
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Active Transport
 * <span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 'Tahoma','sans-serif'">Vesicles

Links to Study Material: [|Cell Membrane Quiz] [|Cell Membrane Quiz #2] [|Diffusion Video] [|Crossword Puzzle] [|Cell Wall Information]

Bibliogrpahy: "Eucaryotic Cell Interactive Animation." __Cells Alive!__. 2006. 28 Oct 2008 <http://www.cellsalive.com/cells/cell_model.htm>. "Cell Membranes." __Biology4kids.com__. 2004. 28 Oct 2008 <http://www.biology4kids.com/files/cell_membrane.html>. "Cell Wall." __Biology4kids.com__. 2004. 28 Oct 2008 <http://www.biology4kids.com/files/cell_wall.html>. "The Structure of The Cell Membrane." __mcdowellscience.wikispaces.com__. 28 Oct 2008 < [| http://mcdowellscience.wikispaces.com/file/view/The+Structure+of+the+Cell+Membrane.doc]>.