1. “Keeping it all Together”
Cell Membrane
“Keeping it all Together”

2. Cell Membrane
When you think about a membrane, imagine it is like a big plastic bag with some tiny holes.
That bag holds all of the cell pieces and fluids inside the cell and keeps any nasty things outside the cell. The holes are there to let some things move in and out of the cell.

3. Cell Membrane cont…
The cell membrane is what defines the cell and keeps its components separate from outside cells or organisms.

4. Cell membrane
The cell membrane is composed of a double layer of fat cells called a lipid bilayer in which membrane proteins are embedded.
The structure of the lipid bilayer prevents the free passage of most molecules into and out of the cell.

5. Cell Membrane
Fluid Mosaic Model:

6. Cell Membrane
The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer.
The cell membrane regulates what enters and leaves the cell.
Lipid bilayer

7. The Lipid Bilayer
The lipid bilayer is a universal component of all cell membranes
Its role is critical because its structural components provide the barrier that marks the boundaries of a cell.
The structure is called a "lipid bilayer" because it is composed of two layers of fat cells organized in two sheets.

8. Lipid Bilayer Structure
The structure of the lipid bilayer explains its function as a barrier
Lipids are fats, like oil, that are insoluble in water. There are two important regions of a lipid that provide the structure of the lipid bilayer.

9. Lipid Bilayer Structure cont…
Each lipid molecule contains a hydrophilic region or polar head region and a hydrophobic region or non polar tail region.
The hydrophilic region is attracted to aqueous water conditions while the hydrophobic region is repelled from such conditions

10. Phospholipids
The most abundant class of lipid molecule found in cell membranes is the phospholipid.

11. Basic Structure!!

12. Properties of Lipid Bilayer
Most important property is that it is highly impermeable.
Impermeable means it does not allow molecules to pass through it easily
Some molecules require the assistance of other structures.

13. Another Bilayer Property:
Another property of the bilayer is it’s fluidity.
The bilayer contains lipids and proteins
The bilayer's fluidity allows these structures mobility within the lipid bilayer

14. Quiz Checkpoint:
What is the main function of the lipid bilayer?

15. Answer to Question #1
The lipid bilayer acts as a barrier between the inside and outside of the cell. It is highly impermeable and does not allow most molecules to freely pass through it into or out of the cell.

16. Quiz Question #2
Why is the structure called a lipid bilayer?

17. Answer to Question #2
It is called a lipid bilayer because it is composed of two layers of fat, or lipid, molecules.

18. Quiz Question #3 – Fill in the Blank
A phospholipid molecule contains two distinct regions. The __________ region is attracted to water and the ___________ region is repelled from water.

19. Answers to Question #3
Hydrophilic; Hydrophobic

20. Membrane Proteins
While the lipid bilayer provides the structure for the cell membrane, membrane proteins allow for many of the interactions that occur between cells.

21. Membrane Proteins cont…
Membrane proteins perform various functions, and this diversity is reflected in the significantly different types of proteins associated with the lipid bilayer.

22. Classifying Membrane Proteins
Proteins are generally broken down into the smaller classifications of integral proteins, peripheral proteins, and transmembrane proteins…(type of integral)

23. Integral Proteins
Integral proteins are embedded within the lipid bilayer.
They cannot easily be removed from the cell membrane without the use of harsh detergents that destroy the lipid bilayer.
Integral proteins float rather freely within the bilayer, much like oceans in the sea.

24. Peripheral Proteins
Peripheral proteins are attached to the exterior of the lipid bilayer.
They are easily separable from the lipid bilayer, able to be removed without harming the bilayer in any way.
Peripheral proteins are less mobile within the lipid bilayer

25. Transmembrane Proteins
Lipid-bound proteins are located entirely within the boundaries of the lipid bilayer
Often act as “channels” for molecules to pass through the membrane!

26. The Cell Membrane

27. Membrane Transport
We have discussed how the lipid bilayer acts as an efficient barrier by only allowing a very small number of non-polar molecules to freely enter or exit a cell. While for the most part this selectivity is a valuable function and allows the cell to maintain its integrity, cells do need to move certain large, polar molecules such as amino acids, sugars, and nucleotides across their membranes. As a result, cell membranes require specific structures that allow for the transport of certain molecules.

28. Membrane Transport
There are a number of different ways that molecules can pass from one side of a cell membrane to the other
Some such means, like diffusion and osmosis, are natural processes that require no expenditure of energy from the cell and are called passive transport.

29. Passive Transport – Written notes 
Diffusion is the natural phenomenon in which nonpolar molecules naturally flow from an area of HIGH concentration to an area of LOW concentration. Diffusion DOES NOT require energy Figure 7-14 in text OSMOSIS is a similar process, but refers specifically to water molecules Figure 7-16 in text

30. Transport across the membrane: l

31. Draw this: Cytolysis & Plasmolysis
HYPOTONIC
Plasmolysis/
HYPERTONIC

32. Written Notes: Active Transport
Other methods of transport do require energy and are called ACTIVE transport.
In addition to these two forms of transport, there exist other forms of transport such as exocytosis and endocytosis which will be discussed later.
Moves materials from LOW to HIGH concentration gradient.

33. Checkpoint Quiz
QUESTION 1: The cell membrane is made up of a _____ bilayer. Carbohydrate Lipid Protein None of the Above

34. Quiz
QUESTION 2: All eukaryotic cells are surrounded by a cell membrane. True False

35. Quiz
QUESTION 3: The lipids in the bilayer have tails that are... Hydrophilic Hydrophobic

36. Quiz
Question 4: The heads of the lipids in the cell membrane are... Hydrophilic Hydrophobic

37. Quiz
QUESTION 5: Some molecules can pass through a cell membrane without help. True False

38. Quiz
QUESTION 6: You will also find proteins in the lipid bilayer. True False

39. Quiz
Question #7
When something can move through a cell membrane without using any energy (like diffusion) it is called ___________ transport.
With energy (like larger molecules) it is called ____________ transport.

40. Summary of Transport Passive: (NO ENERGY) Diffusion Osmosis
Facilitated Diffusion
(clip on facilitated diffusion)

41. Summary of Transport ACTIVE (Needs energy) Endocytosis: (in)
ACTIVE (Needs energy)
Endocytosis: (in)
Phagocytosis (food)
Pinocytosis (water)
Exocytosis: (out)
Waste
– CRASH COURSE – SUMMARY!!!!!