1. Cellular Transport
Chapter 7.4

2. Pre-Thinking Power Write
Why is cell transport important?
What kinds of things do cells need?
Does this happen fast or slow?
What characteristic(s) of life are we maintaining?
“How” are substances able to cross a membrane?

3. Answers
Cells need a variety of substances to stay alive and they do this by transporting them across (thru) the membrane
Water, Ions, Glucose, O, Na, K
FAST!
Homeostasis, Metabolism
Substances are in constant motion and in contact with their environment

4. What is Passive Transport?
The movement across the cell membrane that does not require energy.

5. Diffusion
Movement of particles from an area of high concentration to an area of low concentration.

6. Concentration gradient – the process of particles, (solutes) moving through a solution from an area of higher concentration to an area of lower concentration.

7. Equilibrium – when the concentration of solute is the same throughout a system.

8. Examples
Quickly get out of your seats and most of you move towards the back of the room
3 of you move towards the front
Which part of the room has hi concentration and which part has lo?
What will students naturally do to alleviate this problem?

9. Equilibrium
Students should attempt to even out the sides of the room. Some will move and most will stay
When the concentration of students are equal on both sides, our room has maintained equilibrium.
Now, one from each side switch…still in equilibrium?

10. Discussion How does this relate to the cell?
Particles cross the membrane based on amount of substances inside the cell v. outside!
The natural flow (meaning without energy) will always be hi lo
Called “down the gradient”
This is the process of DIFFUSION!

11. But wait, doesn’t the membrane stop particles?
EXPLAIN: Cell Membrane is
selectively permeable
WHY: Polar heads and non-polar tails
EXPLAIN: What can cross?
Interior repels ions and polar molecules
So, small and non-polar molecules can diffuse across quickly and quietly!

12. Osmosis Movement of water across a membrane
Does not require energy (passive)
Movement is based on concentration of the environment
Hypotonic: Watery environment, little particles
Hypertonic: Lo water, lots of substances
Isotonic: equal to the cell environment
                                                    

13. Which way does the water go?
Hypotonic: In the Cell
Hypertonic: Out the Cell
Isotonic: Movement in and out is equal
WHY?
To maintain equilibrium!

14. What is the proper environment?
Hypotonic Isotonic Hypertonic

15. What about the ions and polar molecules?
Can enter, they just need a special door!
ION CHANNEL: transport protein with a polar pore through which ions can pass
Ions responsible for the
electrical charge in the
brain and heart

16. Facilitated Diffusion
Requires no energy, but it does require a transport protein
For big molecules that can’t slide through the membrane
Protein changes shape
and literally “swallows” the
molecule

17. Review Video