1. Date: November 17, 2016
Aim #26: How can the process of diffusion and the structure of the cell membrane help the cell to maintain homeostasis?
HW:
Daily Review of class notes.
Castle Learning GRADED QUIZ due TONIGHT by 10:30PM
Unit 3 Test Tuesday 11/22 (period 5) Wednesday 11/23 (period 1)
Do Now:
Which type of transport requires energy?
Which type of transport does not?
Which type of transport moves from High to Low?
Which type of transport moves from Low to High?

2. Aim #26: How can the process of diffusion and the structure of the cell membrane help the cell maintain homeostasis?

3. 1) What is diffusion?
The net movement of particles from where they are more concentrated to where they are less concentrated.
2) What do we mean when we say concentration?
The amount of a particular substance

4. It’s all about concentration

5. 3) The reason diffusion occurs is because molecules are always…
MOVING

6. Why are particle always moving?
ENERGY
Particles are in constant motion because they have
energy

7. 4) What is the end result of diffusion?
The number of particles are now evenly distributed
This is called: Dynamic Equilibrium

8. YES Dynamic Equilibrium
At this point, the number of particles have spread
themselves out equally throughout the beaker.
5) Are the particles still moving after dynamic equilibrium has been reached?
YES

9. An illustration of diffusion:

10. 6) What are the two conditions for diffusion to occur?
There must be a concentration
gradient
2) There must be no barrier blocking
the movement of particles.

11. What is a concentration gradient?
The difference in concentration
between a region of high
concentration and a region of
lower concentration.
Does this picture illustrate a concentration gradient?

12. What do we mean by a barrier?
Will diffusion take place?
YES
Will diffusion take place now? NO
The particles must be free to move down their
concentration gradient in order for diffusion to
occur.

13. Does diffusion take place across the cell membrane?
Yes, the cell is:
Selectively Permeable

14. Why do some things get through the cell membrane?
Small molecules are more likely to get through the cell membrane compared to big molecules

15. Cell Membranes are: Selectively Permeable
A selectively permeable membrane allows some
substances to cross the membrane more easily
than others and blocks the passage of other
substances altogether.

16. 8) What is facilitated diffusion?
transport proteins help move materials from high to low concentration

17. 9) What is the main job of the cell membrane?
Cell membranes helps organisms maintain _____________ by controlling what substances may enter or leave cells
To stay alive, a cell must exchange materials such as food, water, & wastes with its environment
HOMEOSTASIS
Blank = homeostasis