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