Types Cell transport across the cell 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 membrane Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing”

How things enter and leave the cell 3 different ways Pass directly through the membrane Through a transport/ channel protein Transport Vesicles

Types of transport Passive Transport-(no energy required) Diffusion Osmosis Facilitated Diffusion Active Transport (energy required) Endocytosis Ectocytosis 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 Animations http://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

Isotonic solutions Hypotonic solution Hypertonic solution 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_f acilitated_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 transport Some molecules that are pumped across the membrane include Sodium, 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