The cell membrane is selectively permeable, allowing some substances to pass through while restricting others. There are three main types of passive transport across the membrane: diffusion, osmosis, and facilitated diffusion. Active transport requires energy and transports substances against a concentration gradient using transport proteins. A cell can also use endocytosis to bring substances into the cell enclosed in a vesicle, and exocytosis to release the contents of a vesicle outside the cell.

1. Chapter 3 - Section 2
Moving
Cellular Materials

2. Selectively Permeable
A cell’s membrane is
selectively permeable. It
allows some things to
enter or leave the cell
while keeping other
things outside or inside
the cell.

3. The way in which substances move through a
cell membrane depends on:
1. the size of the particles
2. the path the substance takes through the
membrane
3. whether or not energy is used

4. • The movement of substances through the cell
membrane without the input of energy is
called:
passive transport
• There are 3 types of passive transport:
• diffusion
• osmosis
• facilitated diffusion

5. • Movement of solids, liquids, and gases from an area
where there is relatively more of them into an area
where there is relatively fewer of them is called
diffusion.
• This movement will continue until the relative number
of these molecules is equal in the two areas.
• When this occurs, equilibrium is reached and
diffusion stops.
diffusion

6. diffusion

7. diffusion

8. equilibrium

9. Food Colouring

10. Air Sac
in Lung
lots of O2

11. Air Sac little of O2
in Lung Red
lots of O2 blood cell

12. Air Sac little of O2
in Lung Red
oxygen
lots of O2 blood cell

13. lots of O2
Red
blood cell
skin cells
little O2

14. lots of O2
Red
blood cell
oxygen
skin cells
little O2

15. skin cells
lots of O2

16. skin cells
lots of O2

17. • Water molecules move by diffusion into and out of
cells.
• The diffusion of water through a cell membrane is called
osmosis.
osmosis

18. osmosis

19. water moves
across membrane
osmosis

20. equilibrium

21. • Losing water from a plant cell
causes its cell membrane to
come away from its cell wall.
• This reduces pressure against
its cell wall, and a plant cell
becomes limp.
• Why would a plant cell lose
water?
• The concentration of
substances (salt/sugar etc) is
greater outside of the plant
cell then inside it.

22. • If water around the cells would
move into them, the cells
would fill with water.
• Their cell membranes would
press against their cell walls.
• Pressure would increase, and
the cells would become firm.
• Why would water enter the
plant cell?
• The concentration of
substances inside the cell is
greater then outside the cell.

23. Carrots & Eggs

24. • Some substances pass easily through the cell
membrane by diffusion.
• Other substances, such as glucose molecules, are so
large that they can enter the cell only with the help of
molecules in the cell membrane called transport
proteins.
• This process, a type of passive transport, is known as
facilitated diffusion.
facilitated
diffusion

26. •3 types of Passive Transport:
•diffusion
•osmosis
•facilitated diffusion Review

27. • Sometimes a substance is needed inside a cell even
though the amount of that substance inside the cell is
already greater than the amount outside the cell.
• When an input of energy is required to move materials
through a cell membrane, active transport takes place.
active
transport

29. active
transport

30. active
transport

31. active
transport

32. The Process of Active Transport
1. The transport protein binds to the
needed particle.
2. Energy is used to move the particle
through the cell membrane.
3. The protein channel changes shape
and pushes the particle.
4. The particle is released by the
transport protein.
active
transport

33. • The roots of a plant already might
contain more mineral molecules
than the surrounding soil does.
• Normally the mineral molecules
move out of the root by diffusion
or facilitated diffusion. But there
are cases where the plant would
still need more minerals.
• The minerals would then need to
move across the membrane and
into the cell, from a low
concentration to a high
concentration.
• To do this energy is needed.

34. • Large protein molecules and
bacteria cannot enter a cell by
diffusion or by using the cell
membrane transport proteins.
• They can enter by being Endocytosis
surrounded by the cell membrane.
and
Exocytosis

35. • The cell membrane folds in on
itself, enclosing the item in a
sphere called a vesicle.
• This process of taking substances
into a cell by surrounding it with
the cell membrane is called
endocytosis.
• Some one-celled organisms take in
food this way.

38. • The contents of a vesicle can be released by a cell using
the process called exocytosis.
• The opposite process is called endocytosis.
• A vesicle’s membrane fuses with a cell’s membrane, and
the vesicle’s contents are released.
• Cells in your stomach use this process to release
chemicals that help digest food.

39. Turn to Page 81