The Cell Membrane; Active

& Passive Transport

The Cell Membrane• Gatekeeper• Regulates what comes in and out of the

cell - selectively permeable • Main components:

•Proteins-Play role in selective transport of materials and act as receptors of information containing molecules

•Phospholipids-play role in water absorption and secretion

Cell Wall• Found only in plant cells and

certain bacteria cells• Main function is support

Solutions• Mixtures of substances• Solute (salt or sugar) and solvent

(water)• Examples: salt + water; sugar +

water

Passive Transport

•Requires NO energy•Diffusion & Osmosis•Facilitated Diffusion –

carrier proteins “help” molecules across

the membrane

Diffusion•The movement of molecules

from an area of high concentration to an area of low concentration

•Molecules tend to “spread out”

•Requires no energy

Equilibrium

• When molecules are evenly spread throughout a space

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Osmosis•The diffusion of water across a membrane

•The cell membrane is selectively permeable

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Rule for Osmosis

If the area outside the cell has more salt – then water will be sucked out

of the cell

Cells In Different Solutions

Isotonic•Same amount of solute inside cell as outside of cell•Water moving out of cell is equal to water moving into cell

ISO = the same

Hypotonic•Cell may burst, or organelles called “contractile vacuoles” remove excess water•Water moving into cell faster than water moving out of cell

Hypo = less

Hypertonic•Cell will shrink or die, plants wilt•Water moving out of cell faster than water moving in

Hyper = more

ACTIVE TRANSPORT• Requires the cell to use energy• Proteins or Pumps found in the

membrane move materials across

Endocytosis

•Taking “in” large molecules by the cell

Exocytosis•Removing large particles (waste)

from the cell•Stuff “exits” the cell

http://www.esnips.com/doc/2dad912f-9dcc-4936-89d9-1ae32c6125d2/Chapter-6---Endocytosis-and-Exocytosis

Review

Passive Transport

Active Transport

No energy required

Energy required (ATP)

Examples: Diffusion and

Osmosis

Examples: Endocytosis and

Exocytosis