Unit 6 Cell Transport Part 2

Facilitated Diffusion  Carrier protein in the cell membrane is needed to help move a specific molecule across  Facilitated means to help or make easier  Carrier protein acts like a gate and increases the rate of transport of certain substances  Does not require energy because molecules are moving down the concentration gradient

Glucose moves in and out of the cell this way

Active Transport  Movement of a substance against the concentration gradient from low to high concentration  Movement of molecules that can't cross the cell membrane  Energy is needed and work is done for this type of transport  This is one of the most important uses of our cell energy!

Channels and Carrier Proteins

Ion Channels

Active Transport of Sodium and Potassium

What if I am too large to cross the Cell Membrane?

Endo- and Exo-cytosis Movement of very large molecules (food, waste) into (endo) and out (exo) of the cell The large molecule is enclosed in a "packet" To move into – part of cell membrane surrounds molecule to form a "packet", then pinches off the cell membrane, entering the cell To move out – a "packet" (the molecule surrounded by a membrane) fuses/merges with the cell membrane – molecule released outside the cell

Exocytosis and Endocytosis Exocytosis Exo = Out leaves the cell Endocytosis Endo = In enters the cell