TYPES CELL
TRANSPO
RT
ACROSS THE C
ELL MEMBRANE
CELL MEMBRANE STRUCTURE • Phospholipid Bilayer• Proteins (peripheral and integral)• Carbohydrates
FUNCTIONS OF THE CELL MEMBRANE Protective barrier that regulates transport in
& out of cell (selectively permeable) Provide anchoring sites for filaments of
cytoskeleton Contains the cytoplasm (fluid in cell) Maintain homeostasis (balance between
inside and out)
FLUID MOSAIC MODEL FLUID- because individual phospholipids and
proteins can move around freely within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.
WATER AND THE MEMBRANEPolar heads are hydrophilic “water loving”
Nonpolar tails are hydrophobic “water fearing”
HOW THINGS ENTER AND LEAVE THE CELL
3 different waysPass directly through the membraneThrough a transport/ channel proteinTransport Vesicles
TYPES OF TRANSPORTPassive Transport-(no energy required)DiffusionOsmosisFacilitated DiffusionActive Transport (energy required)EndocytosisEctocytosis Sodium /Potassium Pump
DIFFUSION• Requires no energy and is a passive
movement. • Molecules move from an area of high
concentration to an area of low concentration.
• Examples: Oxygen and water going in, carbon dioxide going out.
DIFFUSION OF LIQUIDS
DIFFUSION ANIMATIONShttp://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html
OSMOSIS
• Diffusion of WATER across a membrane
• Moves from HIGH water potential (low solute) to LOW water potential (high solute)
• No Energy Required
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
OSMOSIS CONDITIONS
Isotonic solutions When the amount of solutes is equal inside and outside of
cell (cell will stay the same)
Hypotonic solution When solutes outside are lower than inside cell (cell will
swell) * more water outside
Hypertonic solution When solutes outside are higher than inside cell (cell will
shrink) * more water inside cell
CELL SHRIVEL AND BURSTING • If a cell has too much water inside, it
will burst open or lyse. (cytolysis)• If a cell has more water outside the cell,
it will shrivel. (plasmolysis)
OSMOSIS IN RED BLOOD CELLS
Isotonic Hypotonic
Hypertonic
FACILITATED DIFFUSION• Occurs when substances
are not able to pass directly through the membrane. (glucose)
• They enter the cell with the aid of transport proteins.
• It occurs along the concentration gradient and does not require energy.
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html
FACILITATED DIFFUSION
TRANSPORT PROTEINS• Channel proteins
are embedded in the cell membrane & have a pore for materials to cross
• Carrier proteins can change shape to move material from one side of the membrane to the other
ACTIVE TRANSPORT• Requires energy • Substances cannot pass directly
through the cell membrane. • Moves against the gradient from
LOW to HIGH Concentrations. • The proteins pump molecules
through the cell membrane. REQUIRES ENERGY in the form of ATP.
ACTIVE TRANSPORTSome molecules that are pumped across
the membrane includeSodium, Potassium, and Calcium Ions
ACTIVE TRANSPORT
SODIUM-POTASSIUM PUMP
Most common example of active transport.
Uses energy to pump sodium and potassium ions through the membrane.
3 Na in; 2 K out
ENDOCYTOSIS/ EXOCYTOSIS• If the molecules are too large to pass through
the membrane, they must use a vesicle to enter and exit. BULK TRANSPORT
• Endocytosis – Big stuff entering • Exocytosis- Big stuff leaving