3. Plasma Membrane of Plant and Animal
Cells
• It is selectively permeable
• Controls which substances are allowed across it
– only allowing certain substances to pass
4. Why is it selectively permeable?
• It regulates what can come in and leave the
cell:
– temperature, pH, blood glucose levels and water
balance
5. Movement Across the Membrane
Passive transport –no
energy used
• Diffusion: Substances
move from high
concentration to low
concentration
• Facilitated diffusion- the
substances move
through a transport
protein.
6. Active Transport
Active transport- movement against concentration
gradient (low to high) with the use of energy.
• Needed to
pump potassium
into the cell and
salt out
• Carrier protein
helps
7. Osmosis (not Jones)
• Water moves from area of
lower solute concentration to
area of higher solute
concentration
• No energy required
• Water never stops moving!
8. Water Regulation
• Isotonic- the concentration of solute inside
the cell is the same as outside the cell –
equilibrium
• Hypotonic- concentration of solute lower
outside the cell than inside the cell
• Hypertonic- concentration of solute is lower
inside the cell than outside the cell
