1. LIPIDS
L2 BIOLOGY

2. Do Now: Key words to look up
Phospholipids
Hydrophilic
Hydrophobic
Cholesterol
Proteins (in cell membrane)
Selectively permeable
Phospholipid bilayer
Fluid mosaic model
AS Biology. Foundation. Cell membranes and Transport

3. What are Lipids? Typical formula C51H98O6
Lipids include substances like fats, oils and waxes
Typical formula C51H98O6
What can you tell me about lipids from looking at this formula?

4. (also called a triglyceride)
Lipid Structure
one glycerol
three fatty acids
(also called a triglyceride)

5. GLYCEROL

6. FATTY ACIDS

7. LIPID=Glycerol +3 fatty acids

8. Two Types of Fatty Acids
SATURATED
The fatty acids are completely full of hydrogen atoms (no double bonds!)
UNSATURATED
There are one or more double bonds

9. Cont…
SATURATED FATS
Usually solid, fully hydrogenated – animal sources

10. Cont…
UNSATURATED FAT
Usually a liquid; not fully hydrogenated plant sources

11. SATURATED OR UNSATURATED?

12. Trans Fats: Bad in your diet!
Unsaturated, but the double bond between carbons is turned so they are now SOLID at room temperature
Considered “bad” fats (we create them artificially from liquid oils)
Margarine, creams in snacks foods

13. 3 functions of Lipids Major component of cell membranes.
Long term energy storage.
Protection.

14. 1. What types of substances are lipids?
2. What are the four parts that make up a lipid?
3. What is the difference between a saturated fat, unsaturated fat, trans fat?
4. How are lipids like proteins?
5. How are lipids different from proteins?

15. -Called a phospholipid bi-layer -What does this mean?
Cell Membranes:
Question: Can We live totally fat Free ?
Every cell is enclosed by a double layer of lipids: that is the cell membrane
-Called a phospholipid bi-layer
-What does this mean?

16. Cell (plasma) Membrane
Encloses the cell’s contents
Function: Regulates which particles (nutrients, wastes) can enter and exit the cell.
Also is way cells “communicate”
Selectively permeable
AS Biology. Foundation. Cell membranes and Transport

17. A Phospholipid Bilayer
Phospholipids can form:
BILAYERS
-2 layers of phospholipids with hydrophilic heads (on outside) and hydrophobic (fatty acid) tails protected inside.
The PHOSPHOLIPID
BILAYER is the basic
structure of membranes.
AS Biology. Foundation. Cell membranes and Transport

18. Properties of Cell Membranes
Basic structure is Phospholipid Bilayer.
Phospholipids have HYDROPHOBIC (non-polar) tails and HYDROPHILIC (polar) heads.
The fatty acid tails of phospholipids can be SATURATED (straight) or UNSATURATED (bent)
AS Biology. Foundation. Cell membranes and Transport

19. Plasma Membrane Structure
Building blocks are phospholipids…
Lipid with a polar phosphate group attached to one end.
AS Biology. Foundation. Cell membranes and Transport

20. Properties of Cell Membranes
Phospholipids act as a barrier to most water soluble substances
BUT, Phospholipids are only PART of the story…………
AS Biology. Foundation. Cell membranes and Transport

21. AS Biology. Foundation. Cell membranes and Transport
Fluid mosaic model
Cell membranes also contain cholesterol and proteins within the phospholipid bilayer.
This ‘model’ for the structure of the membrane is called the: FLUID MOSAIC MODEL
AS Biology. Foundation. Cell membranes and Transport

22. Why call it a Fluid Mosaic Model?
FLUID- because phospholipids and some proteins move around freely within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by scattered protein molecules in the membrane when viewed from above.
AS Biology. Foundation. Cell membranes and Transport

23. Visualizing structure and function
membrane animation
AS Biology. Foundation. Cell membranes and Transport

24. Functions of Proteins/Cholesterol in Cell Membrane
1. Proteins act as channels for substances to move in or out of cell.
2. Some act as membrane enzymes in chemical reactions.
3. Proteins help to stabilize the membrane. Cholesterol stabilizes and prevents ions from entering.
4. glycoproteins act as markers for cell communication or receptors that hormones & other proteins can bind.
AS Biology. Foundation. Cell membranes and Transport

25. Functions of components of cell membranes
Use the following headings to produce a table summarizing the functions of the different types of molecules found in the cell membrane. Use your notes to find the information.
Component Description Function
Phospholipids
Proteins
Cholesterol
AS Biology. Foundation. Cell membranes and Transport

26. AS Biology. Foundation. Cell membranes and Transport
Quick Quiz:
1. What is the main component of the cell membrane?
2. a. What does the word “hydrophobic” mean?
b. What does the word “hydrophilic” mean?
AS Biology. Foundation. Cell membranes and Transport

27. AS Biology. Foundation. Cell membranes and Transport
3. Name 1 function for proteins in the cell membrane.
4. What is the function of cholesterol in the cell membrane?
5 a. What do we call a protein with a carbohydrate (sugar) attached?
b. Name 1 function for these molecules in the membrane.
AS Biology. Foundation. Cell membranes and Transport