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Cell Transport
Two groups of cell transport
 Passive and Active
 What do those terms mean? Discuss
 Passive transport
 Movement in and out of a cell that does NOT require cellular energy
 Active transport
 Movement in and out of a cell that DOES require cellular energy
Passive Transport
(Don’t write down yet – I’ll go over one at a time)
 Diffusion
 Osmosis
 Facilitated Diffusion
Diffusion
 What is diffusion?
 Diffusion: process in which molecules move from an area of high
concentration to low concentration
 Until “dynamic equilibrium” is reached. What is dynamic?
 Dynamic refers to constant movement – once equal, molecules
constantly move in/out at same rate
 Ex) Air freshener
 Diagram on the board
Facilitated Diffusion
 What does “facilitate” mean?
 Facilitated diffusion: process in which molecules move from an area
of high concentration to low concentration through protein channels
in a cell membrane
 Like a door to classroom (with a door monitor)
 Animation
Osmosis
 What is osmosis?
 Osmosis: DIFFUSION of water across a “semi-permeable membrane”
(selectively permeable) to reach equilibrium. What’s that?
 Semi-permeable membrane: a membrane that allows some, but not
all, molecules to pass through it
 Animation
 Diagram on the board
How solution concentration affects osmosis
 What is a “hypotonic” solution?
 Hypotonic: a solution that is LESS concentrated than the cell
 What will occur if a cell is placed in a hypotonic solution?
 Water will enter it
 Animal cells will rupture ”lysis”
 Plant, fungi, bacteria cells remain about the same size. Why?
 What is a “hypertonic” solution?
 Hypertonic: a solution that is MORE concentrated than the cell
 What will occur if a cell is placed in a hypertonic solution?
 Water will leave the cells
 Animal cells will shrink
 Plant, fungi, bacteria cells will stay about the same size. Why?
 What is an “isotonic” solution?
 Isotonic: a solution that has the same concentration as the cell
Let’s review the rest of the homework
Active Transport
(Don’t write down yet – I’ll go over one at a time)
 Active molecular transport
 Endocytosis
 Exocytosis
Active Molecular Transport (“Active diffusion”)
 What does “active molecular transport” suggest?
 Active Molecular Transport: Movement of materials through protein
channels in a cell membrane; these channels require energy to function
 Like facilitated diffusion – but it takes energy
 Like a door to classroom (with a door monitor that throws students in/out)
 Animation
Endocytosis
 Anyone heard of it?
 Endocytosis: the movement of the cell membrane that allows larger
particles to be captured and moved into a cell
 Animation
Exocytosis
 Guesses?
 Exocytosis: the movement of the cell membrane that allows larger
particles to be released from a cell
 Animation