Chapter 5.3 Summary

- Oil's inability to mix with water is typical of the class of water-avoiding compunds called lipids.

- Water-avoiding molecules are said to be hydrophobic.

- Lipids act as a boundary that surrounds and contains the aqueous contents of your cells.

- A fat consists of a tree-carbon backbone called glycerol attached to three fatty acids, which contain long hydrocarbon chains.

- A saturated fat is a fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms.
- An unsaturated fat contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains because some of its carbon atoms are double-bonded to each other.

- A lipid molecule in which the carbon skeleton forms four fused rings

- Cholesterol is an essential molecule found in the membrances that surround your cells.

Concept checks 5.3

1. What property do lipids share?

water-avoiding molecules

2. What are the parts of a fat molecule?

glycerol

3. Describe two ways that steroids differ from fats.

They are different from fats in structure and function. Some steroids circulate in your body as chemical signals. Perhaps the best-known steroid is chloesterol. It is an essential molecule found in the membranes that surround your cells. It is also the starting point from which your body produces other steroids.

4. What does the term unsaturated fat on a food label mean?

Means that it contains less than the maximum number of hydrogen atoms in one or more of its fatty acid cahins.