This document discusses key concepts about cell membranes and transport. It explains that cell membranes are semi-permeable and regulate movement of molecules in and out of cells. Small molecules can pass through via diffusion down their concentration gradient, while larger molecules require channel proteins. Water transport occurs via osmosis. The direction of osmosis depends on the solution concentrations inside and outside the cell. Active transport requires energy and moves molecules against their concentration gradient.

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.