Homeostasis = internal balance Transport = movement of materials Wastes move out of the cell Food and water move into the cell. Cells need to constantly moves molecules across membrane to try to reach equilibrium (equal balance). Never truly reached.

Cell Membrane Phospholipid bilayer. Has Proteins embedded within it. Semi or Selectively Permeable (only certain molecules are allowed to pass)

Terms you need to know.. Solute = the substance BEING dissolved –Sugar –Salt Solvent = the liquid doing the dissolving –water

(Solvent)

Passive Transport Movement of materials WITHOUT energy (ATP)! Move from high concentration to low concentration Types of PASSIVE transport Diffusion Facilitated Diffusion Osmosis

Passive Transport moves.. Small molecules Uncharged molecules (do not have a + or -) Water Gases –Oxygen –Carbon Dioxide

riding a bike down a hill, no energy is needed. Passive Transport is like….

So…does Passive Transport require energy to move molecules in or out of the cell? NO!

Diffusion Type of PASSIVE transport (no energy) Movement of molecules across the membrane down the concentration gradient. –High to a low concentration. –“Spreading Out” of molecules –Always trying to reach “equilibrium” (molecules evenly spread out)

Rate of diffusion is driven by kinetic energy ~The more KE, the faster the rate of diffusion ~Temperature (hot is faster than cold) ~Motion

Equilibrium Molecules are balanced equally inside and outside of cell. The cell is always trying to reach/maintain this! (since molecules are always in motion)

Osmosis Type of PASSIVE transport (no energy) The diffusion of WATER molecules across a membrane. Movement of water from area of high water concentration to an area of low water concentration. Always trying to reach “equilibrium” (molecules evenly spread out)

What causes the water to move? Concentration gradient of solutes –A difference of solute concentration between the inside and outside of a cell “Solutes Suck” –Water will move to the area with the greater solute concentration

Diffusion of water Example: Sugar and water. Sugar = solute (being dissolved) Water = solvent (doing the dissolving_

Based on the concept of osmosis, what would you expect to happen in this setup? A.No movement of water will occur. B.Water will move in both directions equally. C.The net movement of water will be from side B to side A. D.The net movement of water will be from side A to side B.

SOLUTES SUCK!!!!

Osmosis Notes Hypotonic solution – concentration of solutes is greater inside the cell than outside. –Water enters cell. Cell swells, gets bigger Isotonic solution – the concentration of solutes is the same inside and outside of cell. –Equal water moving in as out. Hypertonic solution – concentration of solutes is greater outside the cell than inside. –Water leaves cell. Cell shrinks, gets smaller

Imagine that the membrane shown below is impermeable to the solute molecules but permeable to water. Which way will water flow? A.left to right B.right to left

Facilitated Diffusion Type of PASSIVE transport (no energy) Diffusion of a substance across the membrane with the help of a protein embedded in a membrane. Movement is assisted Still moving molecules from high to low

Active Transport REQUIRES ATP!!! (energy) Takes work from cell’s mitochondria Movement of molecules across the membrane against (up) the concentration gradient From LOW to HIGH concentration Types of Active Pumps (proteins) Endocytosis Exocytosis = ENERGY

Active Transport moves… very LARGE molecules Charged molecules (ions) –Na+ –K+ –Cl-

Movement of squares (low to high concentraion )

Active Transport is like… riding a bike up a hill, ENERGY is required.

Types of Active Transport Sodium Potassium (Ion) Pump This is where the concentration is moving “low to high concentraion” Uses proteins in membrane to “pump” ions against concentration gradient Ions are elements with a charge ( + or - )

Exocytosis (type of active transport) Movement of large molecules OUT of the cell Molecules surrounded by bilayer vesicle (from Golgi) Membrane absorbs bilayer vesicle (seals back up) Large molecules pushed out

Endocytosis (type of active transport) Movement of large molecules INTO the cell. Membrane starts to make a inward fold (dip) Large molecules move into that opening/pocket Membrane surrounds the molecules with bilayer (creating a vesicle) Vesicle (molecules inside it) moves into the cell Membrane seals back up

Summary of Passive vs. Active Transport Passive NO energy High to Low Down the concentration gradient Diffusion Osmosis Facilitated Diffusion Active Requires energy (ATP) Low to High Up the concentration gradient Endocytosis Exocytosis

Summary of Passive vs. Active Transport Passive Can move…. Small molecules Uncharged molecules Water Gases –Carbon Dioxide –Oxygen Active Can move…. LARGE molecules Charged molecules (ions: Na+, K+, Cl-)

Summary of Passive vs. Active Transport What do both types of cell transport have in common (similarities)? Movement of molecules in/out of cell membrane Trying to reach equilibrium Helps cell maintain homeostasis – stable internal balance needed for the cell’s survival