1. Section C: Lipids - Diverse Hydrophobic Molecules
CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES
HW 1-4
Section C: Lipids - Diverse Hydrophobic Molecules
1. Fats store large amounts of energy
2. Phospholipids are major components of cell membranes
3. Steroids include cholesterol and certain hormones
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

2. Properties of Lipids Lipids are NOT POLYMERS
Lipids are HIGHLY DIVERSE in STRUCTURE and FUNCTION
HYDROPHOBIC- Lipids have little or no affinity for water

3. USES OF FAT: INSULATION

4. Uses of Fat: Long-Term Energy Storage
FAT CONTAINS ABOUT 2X AS MUCH ENERGY PER GRAM AS SUGAR
“FAT RICH” Bear about to hibernate for winter
“Svelte” Spring Time Look
(After living off stored fat reserves over the winter)

6. Storing Energy in Plants vs Animals
Animals need to be light to move fast!
Fat = low density but high energy content, i.e. small mass and volume stores a lot of energy. (Optimize ratio of muscle to fat)
Plants are anchored in one place. Energy can be stored primarily in starch. Plants tend to have much lower fat content.

7. USES OF FAT: CELL MEMBRANES
(form compartments in cells)
HORMONES AND STERIODS – chemical regulation
VITAMIN STORAGE – some vitamins are only soluble in fat tissue.

9. STRUCTURE OF FATTY ACIDS
Hydrocarbon chain = Energy rich
Carboxylic Acid Group
Fatty Acids Can Vary in LENGTH AND SHAPE

10. What key bonding feature causes the shapes of these two fatty acids to be different?
The presence of double bonds can cause kinks in the hydrocarbon chain.

11. The kinks in a hydrocarbon chain are the result of the lack of free rotation around a C= C double bond

12. Link to Sigma and Pi Bonds (Show ethylene only)
Double bonds are formed by a sigma (straight-on overlap) and a pi bond (overlap of parallel p – orbitals)

13. Cis and Trans Isomers
Geometric isomers produced by double bond

14. Extension: Cis-Trans isomerization is a key part of the chemistry of vision
Link to Vision animation

15. H bonds to C at every possible position
Fig. 5-12
SATURATED FATS
All C-C single bonds
H bonds to C at every possible position
Structural
formula of a
saturated fat
molecule
Stearic acid, a
saturated fatty
acid
Video link sat vs unsaturated
(a) Saturated fat
UNSATURATED FATS
May contains kinks or bends due to lack of free rotation around C=C double bonds
Figure 5.12 Examples of saturated and unsaturated fats and fatty acids
Structural formula
of an unsaturated
fat molecule
Oleic acid, an
unsaturated
fatty acid
(b) Unsaturated fat
cis double
bond causes
bending

19. Cis and Trans Fatty Acids

20. Cis Fatty Acids Have Bent Shape; Trans-Fatty Acids are more linear

22. Carbons opposite sides of C=C bond
Carbons Same side of C=C bond

23. IB MEMORIZE THIS RXN FOR TEST!