1. Chapter 5
Lipids

2. Lipids Large biological molecules that do not form polymers
Have little or no affinity for water – hydrophobic
Consist mostly of hydrocarbons
Include fats, phospholipids, steroids, waxes, and certain pigments
Composed of a glycerol molecule and 3 fatty acids forming a triglyceride

3. Saturated Fats
No double bonds between the carbons; therefore, the carbons are said to be “saturated” with hydrogens
Include most animal fats
Are solid at room temperature – lard and butter
“hydrogenated vegetable oils” – such as peanut butter and margarine - are unsaturated fats that have been synthetically converted to saturated fats with the addition of hydrogen

4. Saturated Fats
A diet rich in saturated fats contributes to the cardiovascular disease, atherosclerosis

5. Unsaturated Fats Have one or more double bonds
Will have a “kink” in its tail where the double bonds occur
Fats from plants and fish
Usually liquid at room temperature (oils)
The kinks caused by the double bonds prevent the fat from solidifying at room temperature

6. Importance of Fats
Despite their negative “rap,” fats are important to living things
Major function is storing energy
1 gram of fat stores over twice as much energy as 1 gram of polysaccharide (i.e. starch)
In animals, fat also serves to cushion vital organs and fat under the skin insulates the body
In marine mammals, such as seals and whales, fat makes up blubber

7. Phospholipids Have only 2 fatty acid tails instead of three
A phosphate group is attached to the third hydroxyl group of the glycerol
The tails are hydrophobic and the head is hydrophilic

8. Phospholipids
In water, phospholipids arrange themselves so the hydrophobic tails do not touch water

9. Steroids A carbon skeleton consisting of four fused rings
Example: cholesterol
common component of animal cell membranes
precursor from which other steroids are synthesized (i.e. sex hormones)
too much in the blood can cause atherosclerosis