Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings These compounds are...

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• 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

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• 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

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• 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

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• 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.