1. Passive and Active Transport
Outcomes:
Identify the factors which influence the rate and direction of diffusion.
Identify how osmosis is related to diffusion and the value of osmosis to living organisms.
Examine the mechanisms of active transport by identifying and explaining the two processes.
Compare the similarities and differences between active and passive transport.
**Don’t have to write these out**
Passive and Active Transport
Unit 2- Cell Structure and Function

2. Cellular Transport
Cellular transport moves substances within the cell and moves substances into and out of the cell
There are 2 types:
Passive Transport
Active Transport

3. Passive Transport These types of transport do not require energy
Diffusion
Facilitated Diffusion
Osmosis

4. A) Diffusion
Remember from years before that particles in solids, liquids, and gasses are in constant random motion (Particle Theory of Matter)
Substances dissolved in water move constantly in random motion
The random motion of these particles creates DIFFUSION

5. The amount of a substance in a certain area is called CONCENTRATION
Substances diffuse from an area of higher concentration to an area of lower concentration
Watch the following video and draw the diagram on the next page:

6. Diagram of Diffusion

7. Diffusion occurs until there is an equal concentration of particles in an area/cell
The particles continue to move randomly, but there is no overall change- this is called DYNAMIC EQUILIBRIUM

8. Rate of Diffusion 3 main factors affect the rate that diffusion occurs
Concentration
When concentration is high, diffusion happens quickly because there are more particles to collide with each other
Temperature
When temperature increases, the particles collide more quickly
Pressure
When pressure increases, the particles collide more quickly

9. B) Facilitated Diffusion
While water can diffuse readily across a plasma membrane, most other substances need help
Happens through carrier and channel proteins

10. The CHANNEL PROTEINS in the plasma membrane of the cell are used to diffuse ions and small molecules across the cell membrane (draw the diagram below)

11. CARRIER PROTEINS are also used to move substances across a cell membrane by changing shape to help diffusion in a cell (Draw the diagram)

12. C) Osmosis
The diffusion of water across a selectively permeable membrane is OSMOSIS
Regulating the movement of water across the plasma membrane is an important factor in maintaining homeostasis
(draw the next diagram)

14. If the concentration of solute is higher on one side of the cell membrane, the water will move towards the higher solute concentration
This diffusion happens until dynamic equilibrium occurs

15. Isotonic Solution
When a cell is in a solution that has the same concentration of water and solutes is said to be in an ISOTONIC solution
Water moves into and out of the cell at the same rate and cells keep their normal shape

16. Hypotonic Solution
If a cell is in a solution that has a lower concentration of solute, the cell is said to be in a HYPOTONIC solution
There is more water outside of the cell than inside the cell which causes water to move into the cell
The water moving into the cell creates osmotic pressure

17. In an animal cell, the water may enter the cell so much so that it bursts
A plant cell will not burst if there is a high osmotic pressure because the cell wall is very rigid

18. Hypertonic Solution
When the concentration of the solute outside of the cell is higher than inside
Water moves outside the cell
Animal cells may shrivel because of water loss
Plant cells wilt because the water vacuole is empty

19. Draw the diagram:

20. Video Explanation

21. Active Transport
This happens when substances have to move from an area of lower concentration to an area of higher concentration
This process makes sure that cells have the proper amount of substances inside of them
These forms of cellular transport REQUIRE the use of ENERGY by the cell
Pumps (carrier proteins)
Endocytosis/Exocytosis

22. A) Pumps (Carrier Proteins)
Carrier proteins can move substances against a concentration gradient
Some pumps move one type of substance in one direction across the plasma membrane
Other pumps move two substances in both directions across the plasma membrane

23. Sodium Potassium Pump This is a common type of pump
moves 3 sodium ions out of the cell
moves 2 potassium ions into the cell
ATP (a form of energy) breaks down into ADP to do this
Video demonstration

25. B) Endocytosis & Exocytosis
Particles that are too large to travel through the plasma membrane leave or enter the cell differently

26. Endocytosis
ENDOCYTOSIS is when a cell surrounds something outside of the cell
The cell membrane pinches off and leaves the substance inside the cell
The substance is now in a vesicle to travel throughout the cell

27. Exocytosis
Is when substances leave the cell by vesicles joining the plasma membrane to expel the substance