The Cell Membrane

The Cell Membrane

The cell membrane is the barrier that separates the inside of the cell from the outside. The cell membrane is made up of phospholipids,proteins, and other macromolecules. The phosopholipids make up a bilayer. It contains hydrophilic and hydrophobic molecules. The proteins in the cell membrane are located within the phospholipid bilayer. These proteins determine certain funtctions of the cell membrane. There are three types of proteins.

Peripheral Integral Transmembrane

-loosely bound -penetrate lipid bilayer -transport proteins

-on the surface of the cell -across entire membrane -channels,permeases

-identity markers

Nonpolar amino acids - hyrophobic

polar amino acids - hydrophilic

Antigens are markers of a cell and can tell cells apart. It rejects foreign cells, and lets certain cells enter.

Diffusion - is the movement from high concentration to low ( an easy way of thining of it would be H comes before L in the alphabet). Fats and other lipids can get through the phospholipid bilayer directly by diffusion, other larger molecules such as starch can not get into the cell directly.

Facilitated Diffusion (facilitated=with help, open channel=fast transport). Diffusion of hydrophilic molecules. From High to Low.

Active Transport- diffsuion against concentration. Low to High. ATP is needed.

Osmosis = diffusion of water. High to Low. The survival rate of a cell counts on a balance of water loss and uptake. Determined by amount of solute, and water.

Hypertonic=more solute, and less water.EX-shellfish, plant cells

Hypotonic=less solute, and more water. EX- paramecium

Isotonic=equal solute, and equal water. EX-blood cells in blood