1. Cell Transport

2. Structure of Cell Membrane
Because of its’ structure, it is selectively permeable, meaning it only allows certain substances in and out (like a bouncer at a night club)
The cell membrane is a lipid bilayer, meaning it is made of two layers of lipid.

3. Ways in Which Materials Enter and Leave the Cell

4. Passive Transport vs. Active Transport
Weeee!!!
Passive transport – transport of materials from a higher to lower concentration. Energy is not required for this to occur.
Active transport – transport of materials from a lower to higher concentration. Energy is needed for this to occur.
high
low
This is gonna be hard work!!
high
low

5. 3 Types of Passive Transport:

6. 1. Diffusion
Transport of substances (other than water) from areas of high to low concentration.
Diffusion occurs until the molecules equal on both sides. This is called equilibrium.

7. Diffusion Through Cell Membranes
CO2
CO2
Molecules tend to diffuse across a cell membrane until equilibrium is reached (the same amount of solutes on both sides).
For example:
The capillary to the right is returning blood to the lungs. It has a high concentration of carbon dioxide. The air sacs in the lungs have a lower concentration of carbon dioxide.
Which way will the carbon dioxide go?
CO2
CO2
CO2
CO2
CO2
CO2
Capillary (bloodstream)
air sacs

8. Examples of Diffusion:
Perfume spreading from one area across the room
Kool Aid powder spreading in water to make Kool Aid
Oxygen going into body cells

9. 2. Facilitated Diffusion
Diffusion of large molecules with the aid of carrier proteins, located in the cell membrane, from high to low concentration
Facilitated diffusion occurs for very large molecules such as glucose, ions, and proteins.

10. Examples of Facilitated Diffusion:
Snake venom being release from the special cells that make it
Glucose going into the cell so it can be broken down
Ions going into and out of muscles so they can contract
Ions going into and out of nerve cells so they can send an impulse

11. 3. Osmosis
The diffusion of water across a selectively permeable membrane (high to low concentration)

12. Notice the water rises on the left side of the tube, as water moves from right to left.
The sugar concentration is higher on the left, so water moves through the membrane until the solutions are about equal in terms of sugar concentration

13. Types of Solutions or Environments for a Cell:
3 Situations for Osmosis…Which way will the water go?

14. Isotonic Solutions:
There is an equal concentration of water and solutes both in and outside the cell.
Water moves equally in both directions.
Ideally, this is the state a cell wants to be in.

15. Hypotonic Solutions:
The environment around the cell has a higher concentration of water than the cell.
Water moves into the cell.
The cell begins to swell, and may burst.

16. Hypertonic Solutions:
The cell has a higher concentration of water than its surroundings.
Water moves out of the cell.
The cell begins to shrink, and may shrivel and die if it continues.

17. Hypertonic, Hypotonic, or Isotonic?
A balloon has a higher salt concentration than its environment. Water diffuses into the balloon faster, swelling it until the salt concentrations in and out are equal.

18. Answer: HYPOTONIC
Most freshwater fish have a special organ that pumps out the excess water as it rushes into their body. If they did not have some way to combat this, their cells will burst (cytolysis) and the fish would die.

19. Hypertonic, Hypotonic, or Isotonic?
A balloon has a lower salt concentration than its environment. Water diffuses out of the balloon, shrinking it until the salt concentrations in and out are equal.

20. Answer: HYPERTONIC
Fish living in the ocean must have a way to deal with the high salt environment of the ocean, or their cells would shrivel (plasmolysis) and the fish would die. Most ocean fish have high salt concentrations in their body to keep that from happening.

21. Hypertonic, Hypotonic, or Isotonic?
A water-filled balloon has the same salt concentration as its environment. The water diffuses in and out at the same rate. The balloon, therefore, stays the same size.

22. Answer: ISOTONIC
Jellyfish have a high salt concentration inside their body, equaling that of its salt water environment. If it did not have this trait, it would dry up (plasmolysis).

23. Is this plant in a hypertonic, hypotonic, and isotonic environment?
Answer: Hypertonic
Which way did the water go, into or out of the cell?
Answer: Out of the cell
What happened to the plant cells? Did they shrink or burst?
Answer: they shrank

24. Is this plant in a hypertonic, hypotonic, and isotonic environment?
Answer: Hypotonic
Which way did the water go, into or out of the cell?
Answer: into the cell
What happened to the plant? Did the cells burst or shrink?
Answer: they burst

25. Is this plant in a hypertonic, hypotonic, and isotonic environment?
Answer: isotonic
Which way did the water go?
Answer: in and out equally
Why is the plant happy?
Answer: It’s in the type of environment it wants to be in.

26. Question:
How do cells deal with the problem of water rushing into or out of the cell?

27. 1. Cells Are Surrounded by Blood:
Animal cells are bathed in blood.
Blood has a certain amount of proteins, sugars, salts, and other solutes that equal that of the cell.
Why aren’t your body cells surrounded by pure water?

28. Example 1:
When receiving an IV in a hospital, they are pumping fluids with certain concentrations of water, salts, proteins, etc. into your body.
Why do you think IV’s contain these substances, rather than pure water?
What type of environment would your cells be in, if the IV’s did contain pure water?

29. Answer:
Hypotonic

30. Example 2:
When you engage in physical activity, it is recommended that you drink water, rather than coke or other sugary drinks.
What could happen to your body if you do not drink water during physical activity on a hot day?
What type of environment are you creating for your cells?

31. Answer:
Hypertonic

32. 2. Plant Cells Have Cell Walls to Hold them Together
The cell walls of plants help keep the plant’s shape in times of too much or too little water.
High Pressure with High Water
Low Pressure with Low Water

33. Is the pressure of the cell wall high or low?
What type of environment do you think these plant cells are in?
Is the pressure of the cell wall high or low?
What type of environment do you think these plant cells are in?

34. Think About It…
Plants wilt when the pressure of the cell wall on the plant cell (increases / decreases).
A wilted plant will regain its shape when the amount of water (increases / decreases).

35. 3. Some Cells Have Contractile Vacuoles
Some organisms, such as the paramecium, have contractile vacuoles to pump out excess water.

36. Think About It…
If the paramecium did not pump out the excess water it would (shrink / pop)
If the paramecium were placed in a salt water environment it would (shrink / pop).

37. Active Transport
Transport of substances from high to low concentrations. This requires energy.

38. Active Transport There are two types:
Endocytosis – takes materials into the cell (low to high concentration)
Exocytosis – materials exit the cell (low to high concentration)

39. Types of Endocytosis

40. Examples of Endocytosis
Macrophage (white blood cell) engulfing bacteria
Amoeba engulfing food.