Lipids: Fats & Oils
AP Biology
AP Biology
Lipids
energy storage
AP Biology
2006-2007
Lipids
 Lipids are composed of C, H, O
 4 groups:
fats
 oils
 waxes
 steroids

 Do not form polymers
big molecules made of smaller subunits
 not a continuing chain

AP Biology
Lipids
Six functions of lipids:
1. Long term energy storage
2. Protection against heat loss
(insulation)
3. Protection against physical shock
4. Protection against water loss
5. Chemical messengers (hormones)
6. Major component of membranes
(phospholipids)
AP Biology
Fats store energy
 Function:

energy storage
 2x energy of
carbohydrates
cushion organs
 insulates body

 think whale blubber!
AP Biology
Why do humans
like fatty foods?
Fat subunits
 Structure:

glycerol (3C alcohol) + fatty acid
 fatty acid =
long “tail” with COOH group at “head”
dehydration synthesis
AP Biology
Fatty Acid Structure
•Carboxyl group (COOH) forms the acid.
•“R” group is a hydrocarbon chain (chain of hydrogens and carbons).
A Representative Fatty Acid
Carboxyl
Group
Hydrocarbon
Group
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
AP Biology
Unsaturated
Fatty Acid
Saturated
Fatty Acid
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
mono-unsaturated?
poly-unsaturated?
AP Biology
Saturated vs. unsaturated
saturated
unsaturated
AP Biology
Waxes
• Ear wax – protection from foreign materials/ invaders
(such as insects)
• Wax coating on leaves – forms a barrier to keep water
in leaves
AP Biology
Steroids
 Cholesterol

Found in cell membranes – keeps them
flexible
 Hormones (chemical messengers)
AP Biology
Quiz
1.
2.
3.
4.
5.
6.
7.
8.
What are the four types of lipids ?
Name as many functions of lipids as possible (6).
What is the difference in saturated & unsaturated ?
How could you tell the difference in saturated &
unsaturated by looking at an item ?
What is healthier, saturated or unsaturated fats ?
Lipids contain more energy than carbs, so why are
carbs are primary energy source ?
What is the monomer & polymer of lipids ?
Structurally, how do you tell the difference in carbs
& lipids ?
AP Biology
Answers
1. Fats, oils, waxes, & steroids
2. Energy storage, insulation, protection from water loss,
3.
4.
5.
6.
7.
8.
protection against physical shocks, chemical
messengers, component of cell membranes
C=C double bonds are in unsaturated
Saturated are solid at room temp., unsaturated are liquid
at room temp.
unsaturated
Lipids are harder to break down, because they are
insoluble in water
Technically, there are not monomers & polymers
Both contain C,H, & O, but in carbs they are in a 1:2:1
ratio
AP Biology