1. Transport Across the Cell Membrane http://www. youtube. com/watch

2. Cell Membrane Structure bilayer of phospholipids
with proteins imbedded
Functions:
1. Gatekeeper
2. Protects and controls the substances going in and out of the cell 2

3. Things they want to let in: Things they do not want to let out:
3. Cell membrane is Semi-permeable only allow certain things to pass through the membrane.
Things they want to let in:
Things they do not want to let out:
Things they DO NOT want to let in:
The cell tries to let in good things and keep out bad things. Often based on size…small things are allowed in and larger things are kept out or have to be pumped in.
sugar, oxygen, water
carbon dioxide, waste
viruses, bacteria

4. Question 1.
Which statement regarding the functioning of the cell membrane of all organisms is not correct?
The cell membrane forms a boundary that separates the cellular contents from the outside environment.
The cell membrane forms a barrier that keeps all substances that might harm the cell from entering the cell.
The cell membrane controls the movement of molecules into and out of the cell.
The cell membrane is capable of receiving and recognizing chemical signals.

5. Question 2.
In the given diagram of a single-celled organism, that arrows indicate various activities taking place.
Which systems perform these same activities in humans?
Respiratory, nervous and endocrine
Excretory, respiratory, and reproductive
Digestive, circulatory, and immune
Respiratory, excretory, and digestive

6. Receptor Molecules-“cell receptors”
Communication between cells to maintain homeostasis
Protein molecules on the surface of the membrane with specific shapes.
Certain chemicals (i.e. hormone) will match up with shape on the cell membrane signaling that cell to produce a desired product
Target cell is the cell that is a correct match and is influenced by that hormone or enzyme
Click on image

7. Question 3. Cellular communication is illustrated in the diagram below
Information can be sent from
Cell A to Cell B because cell B is able to recognize signal 1
Cell B to Cell A because cell B is able to recognize signal 2
Cell B to Cell A because cell A is able to recognize signal 1
Cell A to Cell B because cell A is able to recognize signal 2

8. Question 4.
Which substance are found on cell surfaces and respond to nerve and hormone signals?
Vitamins and minerals
Subunits of DNA
Receptor molecules
Starches and simple sugars

9. Question 5.
Hormones and secretions of the nervous system are chemical messengers that
Store genetic information
Extract energy from nutrients
Coordinate system interactions
Carry out the circulation of materials

10. Question 6.
In multicelluar organisms, cells must be able to communicate with each other. Structures that enable most cells to communicate with each other are known as
Chloroplasts
Pathogenic agents
Receptor molecules
Antibiotics

11. TRANSPORT ACROSS THE CELL MEMBRANE http://www. youtube. com/watch
Passive Transport
No energy required (ATP)
Includes diffusion, osmosis, and Facilitated Diffusion (carrier proteins “help” molecules across the membrane ie. Like a revolving door)
Active Transport
Energy required
Requires ATP

12. Diffusion http://www.youtube.com/watch?v=SSS3EtKAzYc
molecules move from an area of high concentration to an area of low concentration
Molecules tend to “spread out”
Requires NO energy
Substances that may diffuse:
Oxygen, carbon dioxide, amino acids, water
Click on image

13. Facilitated Diffusion (uses protein carriers)
Many cell membranes have special channels (carrier proteins) that allow molecules to cross it.
These channels help or facilitate diffusion to happen.
Like regular diffusion, will ONLY occur if there is a higher concentration of molecules on one side of the membrane.
Let’s see!

14. Osmosis Water molecules move from HIGH to LOW concentration
Low High
Water molecules move from HIGH to LOW concentration
across a SEMI-PERMEABLE membrane
Only certain molecules, like water, can move freely across the membrane
They want to BALANCE OUT a solution
Therefore, water moves OPPOSITE of other molecules
water
Watch How osmosis works;

15. salt moves out to balance
Example of Osmosis #1
Condition #1: More Water outside of cell
Inside cell = 98% Water, 2% salt
Outside cell = 100% Water, 0% salt
Water moves into cell,
salt moves out to balance
CELL SWELLS or
BURSTS!

16. salt moves in to balance
Example of Osmosis #2
Condition #2: More water inside of cell
Inside cell: 98% Water, 2% Salt
Outside cell: 95% Water, 5% Salt
Water moves out of cell,
salt moves in to balance
CELL SHRIVELS!

17. Basic Rule for Determining types of Osmostic conditions…..
"Salt absorbs"
If the area outside the cell has more salt – then water will be “pulled” out of the cell
Watch the animation

18. Osmotic Pressure
Cells behave differently when placed in different solutions!
This is due to OSMOSIS!
Most cells are ~ 98% water!
Three types of osmotic pressure:
Hypotonic
Hypertonic
Isotonic

19. Isotonic - "ISO" means the same

20. Hypotonic (Hypo = below)
Solution outside of cell has MORE water, less of other materials (i.e., salt)
Therefore, solution is below strength (hypo)
Examples
Animal cells may burst
“contractile vacuoles”
remove excess water

21. Let’s see…Hypotonic Condition
Cell is placed in 100% water
Solution outside of cell has MORE water, less of other materials (i.e., salt)
Therefore, solution is below strength (hypo)
100%
Water ENTERS cell
98%
CELL
SWELLS!

22. HYPERTONIC – “Hyper = above”
Solution outside of cell has LESS water, more of other materials (i.e., salt)
Therefore, solution is above strength (hyper)
Water moves out of cell - Cell will shrink (Plasmolysis) or die, plants wilt
Why is it dangerous to drink sea water?
Why does pouring salt on a slug kill it?

23. Let’s see….Hypertonic Condition
Cell is placed in 95% water
Solution outside of cell has LESS water, more of other materials (i.e., salt)
Therefore, solution is above strength (hyper)
Water LEAVES cell
95%
98%
CELL
SHRINKS!

24. Isotonic - "ISO" means the same
Solution outside of cell has SAME water, same amount of other materials (i.e., salt)
Therefore, solution is equal strength (iso)

25. Let’s see….Isotonic Condition
Cell is placed in 98% water
Solution outside of cell has SAME water, same amount of other materials (i.e., salt)
Therefore, solution is equal strength (iso)
Water moves equally;
Equilibrium exists
98%
CELL
STAYS
THE SAME!
98%

26. Water relations and Cell shape in blood cells
HYPOTONIC
HYPERTONIC

27. Water relations in a plant cell.
hypotonic
Hypertonic

28. Active Transport
Low High
Sometimes, materials will move across the cell membrane AGAINST a concentration gradient.
LOW HIGH
THIS REQUIRES ENERGY!!! Just like pulling something uphill!
Cells get this energy from ATP (Adenosine Triphosphate)
ATP 28

30. Types of Active Transport
Endocytosis - Taking “in” large molecules by the cell
Phagocytosis = “phood”, taking in food particles
Pinocytosis = liquid substances
Exocytosis
Removing large particles (waste) from the cell
Endocytosis
Exocytosis