Cell Membranes

Including:DiffusionOsmosis

Facilitated DiffusionActive Transport

Endo-, Pino-, and Exo- cytosis

Cell Membrane• Also called the plasma membrane, or

"phospholipid bilayer" • Is a selectively permeable lipid bilayer

found in all cells. – Selectively permeable means some

molecules are allowed to go through and some are not.

• It contains a wide variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes

Phospholipids… …are like fats except it has a phosphate

group in place of the fatty acid. This means that phospholipids have a hydrophilic head and hydrophobic tail and this is important because phospholipids self assemble in water into a bi-layer.

Fluid Mosaic Model

Diffusion

• The process bywhich molecules spread from areas ofhigh concentration, to areas of low

concentration.• No energy is required • When the molecules are even

throughout a space - it is called EQUILIBRIUM

Diffusion across a membrane

Osmosis• Osmosis is the

diffusion of water through a selectively permeable membrane down its concentration gradient

• From an area of high water concentration to an area of lower water concentration

Osmotic Pressure

The pressure required to prevent the passage of water through a semi-permeable membrane from a region of low concentration of solutes to one of higher concentration, by osmosis.

Cell walls create this pressure this prevents plant cells from breaking

Isotonic Solution

• A solution that has the same salt concentration as the normal cells of the body and the blood.

Hypertonic Solution

• A solution with a higher salt concentration than in normal cells of the body and the blood

Hypotonic Solution

• A solution with a lower salt concentration than in normal cells of the body and the blood.

Facilitated Diffusion…

…is the spontaneous passage of molecules or ions across a biological membrane passing through specific membrane transport proteins.

Active transport…

– requires energy – Uses membrane proteins – Goes from area of low concentration

to an area of high concentration

Endocytosis……is the process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing it with their cell membrane

• Two Types – Pinocytosis – Phagocytosis

Pinocytosis

• Movement of liquids into the cell

Phagocytosis… movement of solids into the cell

Exocytosis• …is a cellular process where cells

eject waste products or chemical transmitters (such as hormones) from the interior of the cell.

• Exocytosis is similar in function to Endocytosis but works in the opposite direction.