1. Lipids
energy storage

2. LIPIDS Elements Subunit Carbon Hydrogen Oxygen (no ratio) 1 glycerol
3 fatty acids
Fatty acids are hydrophobic: they repel water. (can be amphipathic)

3. Know These functional groups!1
Know These functional groups! 2 3 4 5

4. LIPIDS examples Fats, oils, waxes Myelin sheath Cell membrane
Steroid hormones

5. Lipids Lipids are composed of C, H, O Diverse group fat
long hydrocarbon chain
Diverse group
fats
phospholipids
steroids
Do not form polymers
big molecules made of smaller subunits
not a continuing chain
fat
Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

6. Remember: HO HO HO, we’re GLad Santa is coming!

7. dehydration synthesis
Fat subunits
Structure:
glycerol (3C alcohol) + fatty acid
fatty acid = long HC “tail” with COOH group at “head”
enzyme
Look at structure… What makes them hydrophobic?
Note functional group = carboxyl
dehydration synthesis

8. Building Fats Triacylglycerol 3 fatty acids linked to glycerol
ester linkage = between OH & COOH
BIG FAT molecule!!

9. Dehydration synthesis
enzyme
Pulling the water out to free up the bond
enzyme
enzyme

10. Why do humans like fatty foods?
Fats store energy
Long HC chain
polar or non-polar?
hydrophilic or hydrophobic?
Function:
energy storage
very rich
2x carbohydrates
cushion organs
insulates body
think whale blubber!
What happens when you add oil to water
Why is there a lot of energy stored in fats?
• big molecule
• lots of bonds of stored energy
So why are we attracted to eating fat?
Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage?

11. Fat Saturation (ewww...gross!)
Saturation means “full”, so what could they be full of?
Full of H atoms! And wherever there is a chemical bond, there is stored energy.

12. Saturated fats All C bonded to H No C=C double bonds
long, straight chain
most animal fats
solid at room temp.
contributes to cardiovascular disease (atherosclerosis) = plaque deposits
Mostly animal fats

13. Unsaturated fats C=C double bonds in the fatty acids plant & fish fats
vegetable oils
liquid at room temperature
the kinks made by double bonded C prevent the molecules from packing tightly together
Mostly plant lipids
Think about “natural” peanut butter:
Lots of unsaturated fats Oil separates out
Companies want to make their product easier to use:
Stop the oil from separating Keep oil solid at room temp.
Hydrogenate it = chemically alter to saturate it
Affect nutrition?
mono-unsaturated?
poly-unsaturated?

14. Saturated vs. unsaturated

15. So limit your intake of FAT, eat polyunsaturated fat (why
So limit your intake of FAT, eat polyunsaturated fat (why?) and avoid transfat.
Basically, trans fat is made when manufacturers add hydrogen to vegetable oil--a process called hydrogenation. Hydrogenation increases the shelf life and flavor stability of foods containing these fats.
And raises your LDL cholesterol level putting you at greater risk for heart disease!

16. Ester linkage
Triacyl glycerols =triglycerides, they remove the hydrophillic portion of carboxyl (-COOH)

17. Major Function of Fats
Energy storage: in adipose tissue for humans and other mammals
2X’s as much energy as carbs.
OTHER FUNCTIONS:
-cushions vital organs
(ex. kidney)
-buoyancy
-insulates body
(ex. polar bear)
-waxes (waterproof protection)

18. Human adipose cells swollen with fat!!!!!
As we gain and lose weight, they just swell and shrink.
Humans can grow more fat cells, but can never get rid of them!!
…Makes you think twice about those French fries!!!

19. Advantage of Carbohydrates for Energy Storage
Carbohydrates are more easily digested than lipids- so stored energy can be released more RAPIDLY
Carbohydrates are soluble in water, so they are easier to transport to and from storage sites

20. Advantage of Lipids for Energy Storage
Lipids contain MORE ENERGY per gram than carbs, so stores of lipids are lighter
Lipids are insoluble in water, they do not cause problems with osmosis in the cell

21. Advantage of Carbohydrates for Energy Storage
Carbohydrates are more easily digested than lipids- so stored energy can be released more RAPIDLY
Carbohydrates are soluble in water, so they are easier to transport to and from storage sites

22. It’s just like a penguin…
Phospholipids
Structure:
glycerol + 2 fatty acids + PO4
PO4 negatively charged
It’s just like a penguin…
A head at one end
& a tail at the other!

23. It likes water & also pushes it away!
Phospholipids
Hydrophobic or hydrophilic?
fatty acid tails = hydrophobic
PO4 = hydrophilic head
dual “personality”
It likes water & also pushes it away!
interaction with H2O is complex & very important!

24. Phospholipids in water
Hydrophilic heads attracted to H2O
Hydrophobic tails “hide” from H2O
can self-assemble into “bubbles”
bubble = “micelle”
can also form bilayer
early evolutionary stage of cell?
bilayer

25. Why is this important? Phospholipids create a barrier in water
define outside vs. inside
cell membranes

26. Phospholipids & cells Phospholipids of cell membrane
double layer = bilayer
hydrophilic heads on outside
in contact with aqueous solution outside of cell and inside of cell
hydrophobic tails on inside
form core
forms barrier between cell & external environment
Phospholipid bilayer
Note other molecules in membrane…
Tell them about soap!

27. Steroids ex: cholesterol, sex hormones 4 fused C rings
different steroids created by attaching different functional groups to rings
cholesterol
Steroid abuse link

28. Cholesterol Important cell component animal cell membranes
precursor of all other steroids
including vertebrate sex hormones
high levels in blood may contribute to cardiovascular disease

29. Cholesterol Important component of cell membrane
helps keep cell membranes fluid & flexible

30. From Cholesterol  Sex Hormones
What a big difference a few atoms can make!
Same C skeleton, different functional groups