1. Movement through Cells
Inside Cell
Cell membrane
Movement through Cells
All organisms are made of cells
Cells are mostly liquid.
Surrounding the cells is also liquid.

2. Role of the Cell Membrane
The cell membrane separates the cell from the liquid it is bathed in.
a) It allows only certain particles to enters and leave the cell. Therefore the cell membrane is considered
____________________
Selectively Permeable
b) The cell membrane is made up of two parts:
___________________________
____________________________
protein channels
lipid bilayer

3. Role of the Cell Membrane
Large particles can only enter and exit the cell through the protein channels BUT
Small particles can enter and exit straight through the lipid bilayer!!

4. Particles of liquids + = solution
All particles of matter--atoms or molecules are constantly in motion.
In liquids, the molecules randomly move.*
A solution is made when particles of sugar, salt, or oxygen, etc. are dissolved in liquids +
= solution

5. What is a solution? Liquid mixture of 2 or more substances.
Water - solvent
The substance dissolved in the water - solute
Concentration =
mass of solute/volume of solvent
Concentration is similar to density.

6. Which beaker contains a more concentrated sugar
Problem:
Imagine you have a beaker filled with sugar water.
Imagine you add double the amount of sugar to the water.
Sugar
Which beaker contains a more concentrated sugar
solution?

7. Concentration of Solutions
Molarity (M) = unit of concentration used in biochemistry
The greater the molarity of a solution the greater the concentration.
0.25M sucrose solution (read as 0.25 molar) has half of the concentration of a 0.50M sucrose solution.

8. Particles in solution cross the cell membrane
Particles within an organism must continuously enter and exit the cell through the cell membrane using one of four processes:
Diffusion
Osmosis
Facilitated diffusion
Active transport

9. Diffusion
The movement of a substance (liquid or gas) from areas of high concentration to areas of low concentration.
The motion is random --eventually all particles spread out evenly throughout the solution = equilibrium.

10. Diffusion Demonstration
Food coloring (solute)+ water (solvent).
What do you think will happen over time in the solution? Discuss at table and draw on white board.

11. Diffusion
Once equilibrium is reached, the movement of particles continues, but it is equal in all directions.
Solution remains in equilibrium.
Particles remain equally spaced out.*
See molecular workbench and answer questions. (p1-6)

12. Diffusion Across a Cell Membrane
The cell membrane allows many types of particles (ions, atoms, molecules) to move in and out of the cell by diffusion.
But some types of molecules are not able to cross the membrane.
What determines whether a particle can cross the cell membrane?
Complete Worksheet to find out!

13. Diffusion Across a Cell Membrane
Design an experiment to test the effect of the size of a particle on its ability to diffuse. Your materials:

14. Conclusions for Diffusion:
Small particles diffuse __________ than large particles across a cell membrane
Only substances that can permeate the cell membrane can diffuse across it.
Diffusion occurs from areas of ________concentration of solute particles to areas of ________ concentration.
The movement of particles is always taking place.
faster
high
low
The cell expends NO ENERGY on the process of diffusion

15. Particles dissolved in water cross the cell membrane
Diffusion
Osmosis

16. Osmosis: A special type of diffusion
Diffusion of water through a selectively permeable membrane. Water diffuses from where there is less solute (sugar, salt, etc.) to where there is more solute.
Osmotic pressure is the force that is placed on a selectively permeable membrane due to the flow of water into one side more than the other.
 See molecular workbench and answer questions
OSMOTIC PRESSURE-placed on semipermeable membrane

17. Osmosis:
Osmosis results in equilibrium when the concentration of the solutions is equal on both sides of the membrane. A solution in equilibrium is also referred to as isotonic.

18. Osmosis
Inside cell
Outside cell
When solutions on both sides of the cell membrane do not have equal concentration they are described as hypotonic or hypertonic.
Hypotonic = lower concentration of solute
Hypertonic = higher concentration of solute
Overall Direction of Water flow

19. Osmosis in Animals
At your table: Draw a picture illustrating #1 and #2 below and answer the questions! Use arrows to show the movement of water.
1. What happens if blood cells are placed in a hypertonic (more concentrated) solution? (saltwater)*
2. What happens if blood cells are placed in a hypotonic (less concentrated) solution?
(distilled water)*

20. Osmosis in Animals

21. Osmosis in Animals
Under normal bodily conditions, blood is the liquid that surround the cells.
Blood has the same concentration of solutes as those inside the cell. This means that blood and cytoplasm are ______________________ to each other.
isotonic

22. Osmosis in Plants Healthy Plant
1) What happens if plant cells are placed in a hypertonic solution (example: salt water)? 2) What happens if plant cells are placed in a hypotonic solution (example: distilled water)? 3) What happens if plant cells are placed in an isotonic solution (example: water with minerals)?
Healthy Plant

23. Osmotic Pressure = Pressure created by water moving into a hypertonic cell.
A plant cell is filled with proteins, sugars, salts.
 The cytoplasm of plant cells is more concentrated than fresh water
 The plant cell is hypertonic relative to freshwater
Since freshwater is used to water plants (not blood), the plant cells fill up with water.

24. Osmotic Pressure = Pressure created by water moving into a hypertonic cell.
With your table answer the following question:
Why doesn’t a plant cell burst (like a blood cell) when placed in freshwater? (Hint: What is a MAJOR difference between plant and animal cells?)
Cell Wall is RIGID

25. Osmosis in one-celled organisms
In one-celled organisms the cell does not burst when in a hypotonic solution (for example pond water).
One-celled organisms have mini-pumps called contractile vacuoles. As water enters the cell, it is pumped out by this organelle.

26. Osmosis and Contractile Vacuoles*

27. Osmosis: The cell expends NO ENERGY on osmosis
Because osmosis is a special type of diffusion
The cell expends NO ENERGY on osmosis
Now: Complete Worksheet on OSMOSIS

28. Particles cross the cell membrane
Diffusion
Osmosis
Facilitated diffusion
Active transport

29. Facilitated Diffusion
Movement of specific molecules through protein channels in the cell membrane
The protein channels are specific to a type of particle. Example: glucose moves through a protein channel that is specific to glucose.

30. Facilitated Diffusion
The movement of particles is two ways but always from areas of high concentration (hypertonic) to areas of low concentration (hypotonic).
Cells use facilitated diffusion for substances such as salt, sugars and starches*.
The cell expends no energy on facilitated diffusion.

31. Particles cross the cell membrane
Diffusion
Osmosis
Facilitated diffusion
Active transport

32. Active Transport
Active Transport: Movement of material across the cell membrane in the OPPOSITE direction of diffusion.
During diffusion particles always moves in the direction of high concentration to low concentration (=concentration gradient).
During active transport particles move against the concentration gradient from low concentration to high concentration.

33. Complete Packet on Transport through a Cell Membrane
Active Transport
Because the flow of solute is from an area of LESS concentration to an area of MORE concentration the solute must be pumped by the cell*.  
See molecular workbench.
Complete Packet on Transport through a Cell Membrane
The cell EXPENDS ENERGY (found in molecules of ATP) on Active Transport

34. Connections to Daily Life
You will be assigned an article on a topic with a group of students. Read and discuss the article with your group and present the information to the class…as a poster, as a play, as a song, etc.
Topics
Facilitated diffusion, insulin and diabetes
Diffusion of oxygen into our lungs and emphysema
Diffusion and alcohol
Pregnancy and diffusion of nutrients between mother and fetus.