2. Cell Boundaries
 Every living cell exists in liquid
environment.
 There is liquid on the inside and outside
of a cell.
 One of the most important functions of
the cell membrane is to regulate the
movement of molecules from one side
membrane to the other side.

3. Semi-Permeable
Membrane
 Smaller
molecules can
pass through.
 Larger
molecules
cannot.

4. Diffusion
 Movement particles from high to low
concentration.
 Diffusion will occur until equlibrium is reached.
 This process does NOT require cellular energy
(ATP).

5. Osmosis
 Diffusion of water
across cell
membrane from
high to low
concentration.
 Water molecules
can very easily
pass through cell
membranes,
because they are
small.

6. Solution Concentrations
 The cytoplasm of a cell is solution of many
substances dissolved in water.
 A solution is mixture of two or more
substances.
 The substances dissolved in a solution are
called solutes.
 The concentration of solution refers to
amount of solute dissolved in liquid
(solvent).

7. Solution Solute Solvent

8. Environment of the Cell
 The solution concentration outside the
cell will determine the direction water
moves across the cell membrane.
 The terms hypotonic, hypertonic, and
isotonic are ADJECTIVES! They
describe the environment of the cell!!!

9. Hypertonic Environments
 Low concentration of water/High
concentration solutes outside cell.
 Water diffuses out of the cell and cell
shrinks.

10. Hypotonic Environments
 High concentration of water/Low
concentration solutes outside cell.
 Cells swell with water and may
explode.

11. Isotonic Environment
 Equal concentration of water/solutes
inside and outside the cell.
 Water will move equally in/out cell.

13. 96% Water, 4% salt
98% Water, 2% Salt
97% Water, 3% Salt
95% Water, 5% Salt
98% Water, 2% Salt
98% Water, 2% Salt

14. Osmotic Pressure
 Water pressure that builds up inside a cell due
to a hypotonic environment.
 If pressure is too high, what could happen?
 Osmotic pressure in plants = turgor pressure.
 Cell Wall helps to with stand turgor pressure.

15. Plasmolysis- loss of water
or “wilting” in plants

16. Facilitated Diffusion
 Some particles
are too large to
pass through the
membrane.
 They need help
from channel
proteins.
 This process
does NOT
require energy!
Glucose
Channel
Protein

17. Passive Transport
 Particles moving from high to
low concentration.
 Doesn’t require energy.

18. Active Transport
 Occasionally, particles need
to move “against the
concentration gradient.”
 Particles moving from low to
high concentration.
 Requires energy (ATP).

19. Endocytosis
 Type of active transport.
 Process of taking in large amounts of
food or liquid by means of active
transport.
1. Phagocytosis (cell eating) – Taking in
large clumps of food.
2. Pinocytosis (cell drinking) – Taking in
large amounts of liquid.

20. Exocytosis
 Type of active
transport.
 Forcing contents out
of the cell.
 Method of removing
large amounts of
waste from cell.