1. Concept 5.3: Lipids are a diverse group of hydrophobic molecules
Lipids are the one class of large biological molecules that do not form polymers
The unifying feature of lipids is having little or no affinity for water
Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds
The most biologically important lipids are fats, phospholipids, and steroids
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2. Fats
Fats are constructed from two types of smaller molecules: glycerol and fatty acids
Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon
A fatty acid consists of a carboxyl group attached to a long carbon skeleton
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3. Fatty acid (palmitic acid)
Fig. 5-11
Fatty acid
(palmitic acid)
Glycerol
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
Figure 5.11 The synthesis and structure of a fat, or triacylglycerol
(b) Fat molecule (triacylglycerol)

4. Fatty acid (palmitic acid) Glycerol
Fig. 5-11a
Fatty acid
(palmitic acid)
Glycerol
Figure 5.11 The synthesis and structure of a fat, or triacylglycerol
(a)
Dehydration reaction in the synthesis of a fat

5. Fat molecule (triacylglycerol)
Fig. 5-11b
Ester linkage
Figure 5.11 The synthesis and structure of a fat, or triacylglycerol
(b)
Fat molecule (triacylglycerol)

6. Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats
In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride
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7. Unsaturated fatty acids have one or more double bonds
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
Animation: Fats
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Structural formula of a saturated fat molecule Stearic acid, a
Fig. 5-12
Structural
formula of a
saturated fat
molecule
Stearic acid, a
saturated fatty
acid
(a) Saturated fat
Figure 5.12 Examples of saturated and unsaturated fats and fatty acids
Structural formula
of an unsaturated
fat molecule
Oleic acid, an
unsaturated
fatty acid
cis double
bond causes
bending
(b) Unsaturated fat

9. Structural formula of a saturated fat molecule Stearic acid, a
Fig. 5-12a
Structural
formula of a
saturated fat
molecule
Figure 5.12 Examples of saturated and unsaturated fats and fatty acids
Stearic acid, a
saturated fatty
acid
(a)
Saturated fat

10. unsaturated fatty acid Oleic acid, an cis double bond causes bending
Fig. 5-12b
Structural formula
of an unsaturated
fat molecule
Oleic acid, an
unsaturated
fatty acid
Figure 5.12 Examples of saturated and unsaturated fats and fatty acids
cis double
bond causes
bending
(b)
Unsaturated fat

11. Most animal fats are saturated
Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature
Most animal fats are saturated
Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature
Plant fats and fish fats are usually unsaturated
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12. A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen
Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds
These trans fats may contribute more than saturated fats to cardiovascular disease
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13. The major function of fats is energy storage
Humans and other mammals store their fat in adipose cells
Adipose tissue also cushions vital organs and insulates the body
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14. Phospholipids
In a phospholipid, two fatty acids and a phosphate group are attached to glycerol
The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Choline Hydrophilic head Phosphate Glycerol Fatty acids
Fig. 5-13
Choline
Hydrophilic head
Phosphate
Glycerol
Fatty acids
Hydrophobic tails
Hydrophilic
head
Figure 5.13 The structure of a phospholipid
Hydrophobic
tails
(a)
Structural formula
(b)
Space-filling model
(c)
Phospholipid symbol

16. Choline Phosphate Hydrophilic head Glycerol Fatty acids
Fig. 5-13ab
Choline
Phosphate
Hydrophilic head
Glycerol
Fatty acids
Hydrophobic tails
Figure 5.13 The structure of a phospholipid
(a)
Structural formula
(b)
Space-filling model

17. Phospholipids are the major component of all cell membranes
When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior
The structure of phospholipids results in a bilayer arrangement found in cell membranes
Phospholipids are the major component of all cell membranes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18. Hydrophilic head Hydrophobic tail WATER WATER Fig. 5-14
Figure 5.14 Bilayer structure formed by self-assembly of phospholipids in an aqueous environment
Hydrophobic
tail
WATER

19. Steroids
Steroids are lipids characterized by a carbon skeleton consisting of four fused rings
Cholesterol, an important steroid, is a component in animal cell membranes
Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease
For the Cell Biology Video Space Filling Model of Cholesterol, go to Animation and Video Files.
For the Cell Biology Video Stick Model of Cholesterol, go to Animation and Video Files.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20. Fig. 5-15
Figure 5.15 Cholesterol, a steroid

21. Proteins account for more than 50% of the dry mass of most cells
Concept 5.4: Proteins have many structures, resulting in a wide range of functions
Proteins account for more than 50% of the dry mass of most cells
Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

22. Table 5-1
Table 5-1

23. Animation: Structural Proteins
Animation: Storage Proteins
Animation: Transport Proteins
Animation: Receptor Proteins
Animation: Contractile Proteins
Animation: Defensive Proteins
Animation: Hormonal Proteins
Animation: Sensory Proteins
Animation: Gene Regulatory Proteins
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions
Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life
Animation: Enzymes
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25. Substrate (sucrose) Glucose Enzyme (sucrase) OH H2O Fructose H O
Fig. 5-16
Substrate
(sucrose)
Glucose
Enzyme
(sucrase) OH
H2O
Fructose
Figure 5.16 The catalytic cycle of an enzyme H O

26. Polypeptides are polymers built from the same set of 20 amino acids
A protein consists of one or more polypeptides
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27. Amino acids are organic molecules with carboxyl and amino groups
Amino Acid Monomers
Amino acids are organic molecules with carboxyl and amino groups
Amino acids differ in their properties due to differing side chains, called R groups
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

28. Fig. 5-UN1
 carbon
Amino
group
Carboxyl
group

29. Figure 5.17 The 20 amino acids of proteins
Nonpolar
Glycine
(Gly or G)
Alanine
(Ala or A)
Valine
(Val or V)
Leucine
(Leu or L)
Isoleucine
(Ile or I)
Methionine
(Met or M)
Phenylalanine
(Phe or F)
Trypotphan
(Trp or W)
Proline
(Pro or P)
Polar
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Glutamine
(Gln or Q)
Figure 5.17 The 20 amino acids of proteins
Electrically
charged
Acidic
Basic
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)

30. Nonpolar Glycine (Gly or G) Alanine (Ala or A) Valine (Val or V)
Fig. 5-17a
Nonpolar
Glycine
(Gly or G)
Alanine
(Ala or A)
Valine
(Val or V)
Leucine
(Leu or L)
Isoleucine
(Ile or I)
Figure 5.17 The 20 amino acids of proteins
Methionine
(Met or M)
Phenylalanine
(Phe or F)
Tryptophan
(Trp or W)
Proline
(Pro or P)

31. Polar Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C)
Fig. 5-17b
Polar
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Glutamine
(Gln or Q)
Figure 5.17 The 20 amino acids of proteins

32. Electrically charged Acidic Basic Aspartic acid (Asp or D)
Fig. 5-17c
Electrically
charged
Acidic
Basic
Figure 5.17 The 20 amino acids of proteins
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)