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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