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• These compounds are composed largely of carbon and hydrogen
– They are not true polymers
– They are grouped together because they do not mix with water
3.8 Lipids include fats, which are mostly energy-storage molecules
Figure 3.8A
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• Fats are lipids whose main function is energy storage
– They are also called triglycerides
• A triglyceride molecule consists of one glycerol molecule linked to three fatty acids
Figure 3.8B
Fatty acid
LE 5-11b
Ester linkage
Fat molecule (triacylglycerol)
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• The fatty acids of unsaturated fats (plant oils) contain double bonds
– These prevent them from solidifying at room temperature
• Saturated fats (lard) lack double bonds
– They are solid at room temperature
Figure 3.8C
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds
• Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds
• Unsaturated fatty acids have one or more double bonds
• The major function of fats is energy storage
LE 5-12a
Saturated fat and fatty acid.
Stearic acid
LE 5-12b
Unsaturated fat and fatty acid.
Oleic acid
cis double bondcauses bending
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• Fats made from saturated fatty acids are called saturated fats
• Most animal fats are saturated
• Saturated fats are solid at room temperature
• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Phospholipids are a major component of cell membranes
• Waxes form waterproof coatings
• Steroids are often hormones
3.9 Phospholipids, waxes, and steroids are lipids with a variety of functions
Figure 3.9
LE 5-13
Structural formula Space-filling model Phospholipid symbol
Hydrophilichead
Hydrophobictails
Fatty acids
Choline
Phosphate
Glycerol
Hyd
rop
ho
bic
tai
lsH
ydr o
ph
ilic
hea
d
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Anabolic steroids are usually synthetic variants of testosterone
• Use of these substances can cause serious health problems
3.10 Connection: Anabolic steroids and related substances pose health risks
Figure 3.10
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Paper Lipid Synthesis Activity: Using the paper folding diagram for lipid, do the following…
1. What two compounds are needed to synthesize a lipid?
2. How many carbon atoms does glycerol contain?
3. Place an asterisk(s) (*) on the glycerol molecule to indicate the location where a dehydration synthesis could occur to synthesis a triglyceride.
4. How many fatty acid molecules are found on the folding diagram? Number each fatty acid molecule on the paper. Identify each as a saturated or unsaturated fatty acid.
5. How does cholesterol’s structure differ from a triglyderide?
6. What would need to draw on the folding diagram if you wanted to make a phospholipid?
If time permits, construct (3) additional questions and answer them.