Chapter 5.3 Summary

Lipids include fat and steroids

• Characteristics of Lipids
• Lipids: water-avoiding compounds, eg. oil
• Hydrophobic: water-avoiding molecules
• Lipids are boundaries for containing aqueous contents
• Fats store energy in your body
• Fats
• Fat: A three-carbon backbone called glycerol attached to three fatty acids with long hydrocarbon chains
• Fat cushions organs and provides insulation
• Saturated fat: Fat where all three acid chains contain the maximum number hydrogen atoms (All carbons are single bonded)
• Most animal fats are saturated - solid at room temp
• Unsaturated fat: Less than max number of hydrogen because some carbons are double-bonded
• Fats in fruits, vegetable, and fish are usually unsaturated
• Saturated fat can promote buildup of plaque - lipid-containing deposits - which contributes to heart disease
• Steroids
• Steroid: A lipid whose carbon skeleton forms four fused rings
• Different from fats
• Steroids circulate in your body as chemical signals
• Cholesterol: Essential steroid found in cell membranes
• A starting point for producing other steroids

Concept Check 5.3

1) What property do lipids share?

All lipids are hydrophobic, meaning they avoid water.

2)What are the parts of a fat molecule?

A fat molecule consist of a three carbon backbone called glycerol attached to three fatty acids which contain long hydrocarbon chains.

3) Describe two ways that steroids differ from fats.

Unlike fats, steroids' carbon skeletons are formed by four fused rings. Instead of storing energy in the body, steroids travel around the body as chemical signals.

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

Unsaturated fat means the food contains fat with less than the maximum number of hydrogen atoms in in its fatty acid chains. Unsaturated fat is usually found in fruit, vegetable, and fish products such as corn oil, olive, oil, and other vegetable oils.