Summary of Chapter 5.3

Vocabulary:
lipid: one of a class of water-avoiding compounds
hydrophobic: water fearing
fat: organic compound consisting of a three-carbon back (glycerol) attached to three fatty acids
saturated fat: fat in which all three fatty acids chains contain the maximum possible number of hydrogen atoms
unsaturated fat: fat with less than the maximum number of hydrogens in one or more of its fatty acid chains
steroid: lipid molecules with four fused carbon rings
cholesterol: steroid molecule present in the plasma membranes of animal cells

Lipids include fats and steroids. Lipids are hydrophobic. Fats are stored for later use and the fatty tissues cushion your organs. All the carbon atoms in the fatty acid chains form single bonds with each other, and the rset of their bonds are with hydrogen atoms.

animal fats: lard and butter (both are saturated)

unsaturated fats: fruits, vegetables, fish, corn oil, olive oil, and other vegetable oils

Steroids circulate in your body as chemical signals. Cholesterol is the best-known steroid. Cholesterol has a bad reputation because high levels of cholesterol can increase risks of heart and blood vessel diseases.
Concept Checks:

1. What property do lipids share? Lipids share the property of being hydrophobic ( meaning water-avoiding ).

2. What are the parts of a fat molecule? A fat molecule consists of a three-carbon backbone called glycerol attached to three fatty acids that contain long hydrocarbon chains.

3. Describe two ways that steroids differ from fats. In the body, fats store energy for later use as fatty tissues cushion your organs and steroids circulate around your body as chemical signals. Fats are of glycerol attached to three fatty acids while a steroid is a lipid where the carbon skeleton forms four fused rings.

4. What does the term unsaturated fat on a food label mean? Unsaturated fat means that it contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains because some of the carbon atoms are double bonded to each other.