A Closer Look at Cell Membranes

Fluid Moisaic Model

Mixed compositions of phospholipids, glycolipids, sterols and protein

Adhesion Proteins

Help one cell to adhere to another or to a protein.

Communication Proteins

Match up with identical proteins in the plasma membrane of an adjoinning cell.

Receptor Proteins
Cause target cells to change their activity.

Recognition Proteins

They project above the plasma membrane and identify a cell as nonself or self.

Passive Transport

Carries molecules and susbtances from a place of high concentration to a place of low concentration.

Active Transport

Carries molecules and substances from a place of low concentration to a place of high concentration.

Concentration Gradient

Difference in the number per unit volume of molecules of a substance between two adjoining regions.

Diffusion

Name for the net movement of like molecules or ions down a concentration gradient.

Electric Gradient

Difference in electric charge between adjoining regions.

Pressure Gradient

Difference in pressure exerted per unit volume between two adjoining cells.

Osmosis

Diffusion of water across a selectively permeable membrane, to a region where the water concentration is lower.

Hypotonic Solution*

Concentrations with lower solute.

Hypertonic solutions**

Ones having more solutes.

Isotonic Solute

Show no net osmotic movement.

***

Hydrostatic Pressure

Turgor Pressure that is released by any volume of fluid.

Osmotic Pressure

Measure of the tendency of water to follow its water concentration gradient and move into that flow.

Endocytosis

Small patch of plasma membrane balloons inwardsand pinches off the cytoplasm.

Exocytosis

Vesicles move to the cell surface, and then to the protein-studded lipid bilayer.

Phagocytosis

"Cell eating" Common endocytic pathway.