Cell Boundaries

Cell membrane thin, flexible barriers that surrounds all cells and separate some areas within cells

Cell membrane organelles are surrounded by cell membranes organelles are special structures in cells that perform a specific function (ex: mitochondria, chloroplasts, nucleus) organelles = little organs

Cell membrane composed of phospholipid bilayers

Plasma membrane cell membrane on the outside of the cell regulates (controls) what enters and leaves the cell provides protection and support sometimes just called THE cell membrane

Beginning Watching at 9:42 Phospholipid have two distinct ends CrashCourse Biology Episode #3 You Are What You Eat Beginning Watching at 9:42 Stop Watching at 10:27

Phospholipids Phosphate end Water Soluble Hydrophilic “Water Loving” Lipid end Water Insoluble Hydrophobic “Water Hating”

When placed in water, how will these molecules arrange themselves? into a hollow sphere water hating (insoluble) ends will "stick together"

When placed in water, how will these molecules arrange themselves? will form a bilayer to keep lipid ends away from water outside of the cell and away from the water inside the cell Outside the cell Inside the cell

Phospholipid bilayer as a Barrier The lipid portion in the center is very oil like. This oil like layer repels water, and water-soluble molecules. Most molecules inside or outside of the cell are water-soluble and cannot easily pass through this oil like layer. This layer thus forms a barrier to most molecules trying to pass in or out of a cell.

Membrane Proteins protein molecules embedded within the phospholipid bilayer They may form channels. If small enough, water-soluble molecules can cross the barrier through the protein channel. Other protein molecules are located on the inside or outside surface of the membrane and "transport" or move particular molecules across the membrane using energy.

Membrane Proteins

Cholesterol lipid embedded in the phospholipids of the cell membrane that prevents the membrane from becoming too solid or too fluid helps the cell membrane tolerate temperature changes

Membrane Carbohydrates serve as identifying markers on the outside of cells helps identify the cell and its function to other cells

Membrane Carbohydrates form many of the antigens on the outside surfaces of cells sometimes combine with proteins to form glycoproteins

Cell Wall found in plants, fungi, some protists, and prokaryotes provides a large amount of support and protection for the cell made of the carbohydrate cellulose in plants NOT a barrier to the movement of molecules

Summary Identify one similarity and one difference between a plasma membrane and a cell wall.