CELL TRANSPORT

Homeostasis and Transport Homeostasis – the stable internal conditions of a living thing; maintaining a stable internal environment

Maintaining a Balance Cells must keep the proper concentration of nutrients and water and eliminate wastes. Cells die without homeostasis. The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things.

Passive Transport Molecules move along a concentration gradient – the difference in concentration of the molecules in a space. 3 Types of transport: Diffusion, osmosis and facilitated diffusion

Diffusion Diffusion – the random movement of molecules from an area of high concentration to an area of low concentration until dynamic equilibrium is reached Perfume, food coloring, O2, CO2

Osmosis The diffusion of water across a selectively permeable membrane, from an area of higher concentration to an area of lower concentration until dynamic equilibrium is reached.

3 types of solutions/cell environments The direction of osmosis is determined by the type of solution a cell is in: Hypertonic – the concentration of solute molecules is higher outside the cell than inside, Hypotonic – the concentration is higher inside than outside, or Isotonic – the concentration is the same

Cells in ISOTONIC solution

Cells in HYPOTONIC solution

Cells in HYPERTONIC solution

Facilitated Diffusion A process in which substances move down their concentration gradient across the plasma membrane with the help of transport (carrier) protein molecules. Examples: Sugars and amino acids

Active Transport Movement of molecules and ions against the concentration gradient Moves in the direction of Low  High Energy is used Example: Transport proteins bind to ions, used energy to change shape, flipping ion into cell.

CELL TRANSPORT PASSIVE ACTIVE DIFFUSION OSMOSIS FACILITATED DIFFUSION

Diffusion Osmosis Facilitated diffusion Active transport Takes energy? With or against the concentration gradient? Requires a protein? What kind of molecules

Cell Membrane Organized as double layer of phospholipids called a lipid bilayer.

Cell Membrane Phospholipids have a hydrophilic head and a hydrophobic tail Hydrophillic – water “loving” Hydrophobic – water “fearing” These interactions results in a selectively permeable membrane This helps determine what substances enter and leave the cell

Cell Membrane Proteins are also embedded in the lipid bilayer of the cell membrane This helps recognize substances, which can pass through the cell