1. Lipids

2. Lipids long-term energy storage do not consist of polymers
insoluble in polar substances
structural components of cells –
ex. phospholipids are the major building block in cell membranes
"messengers" (hormones)

3. Lipid Construction
Lipids are composed of three fatty acids covalently bonded to a 3-carbon glycerol
The fatty acids are composed of CH2 units, and are hydrophobic/not water soluble

4. (a) Dehydration reaction in the synthesis of a fat
Fats
Fats
Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids H O H H H H H H H H H H H H H H H H
O H C OH
Glycerol
Fatty acid
(palmitic acid) HO O
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
Figure 5.11
(b) Fat molecule (triacylglycerol)

5. (a) Saturated fat and fatty acid
Saturated fatty acids
Have the maximum number of hydrogen atoms possible
Have no double bonds
(a) Saturated fat and fatty acid
Stearic acid
Figure 5.12

6. Saturated Fats

7. (b) Unsaturated fat and fatty acid
Unsaturated fatty acids
Have one or more double bonds
(b) Unsaturated fat and fatty acid
cis double bond
causes bending
Oleic acid
Figure 5.12

8. Unsaturated Fat

9. Saturated refers to the "saturation" of the molecule by hydrogen atoms
The presence of a double C=C covalent bond reduces the number of hydrogens that can bond to the carbon chain, hence the application of the term "unsaturated“.
Fatty acids can be saturated (meaning they have as many hydrogens bonded to their carbons as possible) or unsaturated (with one or more double bonds connecting their carbons, hence fewer hydrogens).
Fat - solid at room temperature (saturated)
Oil - liquid (unsaturated)

10. Phospholipids Phospholipids Have only two fatty acids
Have a phosphate group instead of a third fatty acid

11. (a) Structural formula (b) Space-filling model
Phospholipid structure
Consists of a hydrophilic “head” and hydrophobic “tails”
CH2 O P CH C
Phosphate
Glycerol
(a) Structural formula
(b) Space-filling model
Fatty acids
(c) Phospholipid
symbol
Hydrophobic tails
Hydrophilic
head
Hydrophobic
tails –
Hydrophilic head
Choline +
Figure 5.13
N(CH3)3

12. The structure of phospholipids
Results in a bilayer arrangement found in cell membranes
Hydrophilic
head
WATER
Hydrophobic
tail
Figure 5.14

13. Cholesterol and steroids
Steroids - lipids characterized by a carbon skeleton consisting of four fused rings HO
CH3
H3C
Figure 5.15

15. One steroid, cholesterol
Is found in cell membranes
Is a precursor for some hormones HO
CH3
H3C
Figure 5.15

16. Cholesterol
Excess cholesterol in the blood has been linked to atherosclerosis, hardening of the arteries.

17. Functions of Fats and Oils
Long term energy storage
Animals convert excess sugars (beyond their glycogen storage capacities) into fats
Plants store excess sugars as starch, although some seeds and fruits have energy stored as oils - corn oil, peanut oil, palm oil, canola oil, and sunflower oil
Fats store six times as much energy as glycogen.

18. Insulation - heat retention
Cushion – protection (body organs, fetus)
Structural components of cells - Phospholipids and glycolipids – cell membranes
Phospholipids are modified so that a phosphate group (PO4-) is added to one of the fatty acids.
The addition of this group makes a polar "head" and two nonpolar "tails".
Waxes – cuticle -waxy layer covering the leaves and stems of many land plants; and protective coverings on skin and fur of animals
Hormones – body regulation