1. MOVEMENT THROUGH THE MEMBRANE Bubble Lab
Section 7-3

2. The cell membrane Function: Selective permeability
Regulates what enters and leaves the cell. Provides protection and support
Selective permeability
Some substances can pass across the cell membrane and others can’t

3. Structure
Phospholipid Bilayer (Fluid Mosaic Model): a double-layer sheet that makes up nearly all membranes.

4. Components of the lipid bilayer
Polar Head
Hydrophilic
“Water Loving”
Lipid Tails
Hydrophobic
“Water Fearing”

5. Why is the lipid bilayer important?
Tough, flexible structure
Strong barrier between the cell and its environment

6. What does it do for the cell?
Allows only certain materials in or out at certain times.
Ions
Glucose
Water
Electrolytes

7. Other membrane structures
Protein molecules
Form channels and pumps that help to move material across the membrane

8. Other Membrane Structures
Carbohydrate molecules
Act like ID markers for the cell
Basis for blood typing: the antigens on the blood cells (A, B, AB) are carbohydrate chains

11. Components of plasma membrane: 2 layers of phosphlipids
Cells live in fluid environments, with water inside and outside the cell.
Components of plasma membrane:
2 layers of phosphlipids
Polar head and nonpolar tail
Integral proteins
Peripheral proteins
Cholesterol
Carbohydrates 11

12. Proteins: Peripheral proteins On inside surface
Proteins:
Peripheral proteins
On inside surface
Held in place by cytoskeletal filaments
Integral proteins
Embedded in membrane, can move laterally 12

13. Cholesterol - strengthens the plasma membrane.
Cholesterol - strengthens the plasma membrane.
Carbohydrates:
Glycoproteins – proteins with carbohydrates attached
Glycolipids – phospholipids with carbohydrates attached 13

14. Functions of membrane proteins
Some help to transport materials across the membrane.
Channel Protein – allows certain molecules or ions to cross membrane freely
Carrier Protein – interacts with certain molecule or ions to help move it across membrane 14

15. Some proteins aid in cell recognition
Glycocalyx - In animal cells, the carbohydrate chains of cell recognition proteins are collectively called this 15

16. Cell recognition protein
Foreign carbohydrate chains are why transplanted tissue is often rejected by the body 16

17. Building A Membrane
Using the materials provided to you, build a model of a cell membrane.
Make a key explaining what pieces represent the Polar Head, Lipid Tails, Protein Molecules, and Carbohydrate Molecules
Have your teacher check your model before you eat it!

18. Diffusion
Definition: The movement of molecules from an area of higher concentration to an area of lower concentration, until equilibrium is reached.
Concentration?
Mass of Solute/Volume of solution (g/L)
Diffusion of Molecules

19. More molecules = More collision
What causes diffusion?
Diffusion is caused by the constant movement and collision of molecules.
More molecules = More collision
The collision cause the molecules to spread out.

20. Diffusion in Cells
Molecules are able to diffuse through the cell membrane and allow the cell to function.
Facilitated Diffusion – some molecules need help from protein channels to cross the cell membrane.
Animation

21. Osmosis (A special kind of diffusion)
Osmosis is the diffusion of water molecules through a selectively permeable membrane.
Selectively Permeable - Osmosis

22. Osmosis
Isotonic – concentration is the same on both sides of the membrane (equilibrium)
Hypertonic – the solution with a greater concentration
Hypotonic – the solution with the lesser concentration.

23. Osmosis Practice
The cytoplasm of Elodea cells is composed of about 70% water molecules and 30% other kinds of molecules.
What happens when the Elodea cells are put into a liquid that is
a. 50 percent water.
b. 70 percent water.
c percent water .

24. Active Transport
Moving down a concentration gradient is like riding a bike down a hill. It doesn’t require energy
Osmosis and diffusion are examples of passive transport!
Moving up a concentration gradient is like riding up a hill. IT REQUIRES ENERGY.

25. Active Transport
Active Transport: is the movement of materials through a cell membrane using energy.
Molecules move from low concentration to high concentration.
Proteins use ATP to pump ions and small molecules against concentration gradient.

26. Types of Active Transport
Endocytosis – the process of taking material into the cell by means of infoldings of the cell membrane.
Phagocytosis – extension of the cytoplasm surround and engulf the particle
Pinocytosis – similar to phagocytosis, but cells take up liquid instead of particles.

27. Types of Active Transport
2. Exocytosis
Large molecules move from inside the cell to outside the cell.
Contractile Vacoule – an organelle that constantly pumps H2O out of the cell.
Animation

28. Specialized Cells
Cells with a specific structure and function and are found in multi-celled organisms.
We have blood cells, brain cells, bone cells, liver cell, skin cells, etc.

29. We are all made of cells
Organ
System
Organs
Tissues
Cells

30. Tissue
Definition: A group of similar cells working together.
Examples

31. Organs
Definition: A groups of tissues working together to perform a specific job.

32. Organ Systems
Definition: Many organs working together to do a specific job.
Can you name all 10 organ systems?

33. 7.3-7.4 Wrap up Questions Explain Diffusion Explain Osmosis
What does selectively permeable mean?
What is facilitated diffusion?
Are phospholipids the only molecules in a cell membrane?
What is active transport?
What are tissues, organs, and organ systems? Give Examples

34. = cell 10% salt 10% salt 20% salt 10% salt 10% salt 20% salt = cell
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker?
= cell
10% salt
10% salt
20% salt
10% salt
20% salt
10% salt
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker?

35. = cell 10% salt 10% salt 20% salt 10% salt 10% salt 20% salt
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic. Label the net flow of water and state what will happen to the cell in each beaker?

36. Cell membrane reading questions
Compare and contrast integral and peripheral proteins.
What are the differences between the two types of transport proteins discussed in the article (use figure 7.10 to help you)
Why are proteins so essential to keeping your cells hydrated?
Explain how diffusion relates to a concentration gradient.