1. Chapter 5: The Structure and Function of Large Biological Molecules

2. Overview: The Molecules of Life
All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids
Macromolecules are large molecules composed of thousands of covalently connected atoms
Structure and function are related!!!!
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3. Concept 5.1: Macromolecules are polymers, built from monomers
A polymer is a long molecule consisting of many similar building blocks
These small building-block molecules are called monomers
Three of the four classes of life’s organic molecules are polymers:
Carbohydrates
Proteins
Nucleic acids
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4. Hydrolysis= addition of water to separate a polymer
Fig. 5-2 HO 1 2 3 H HO H
Condensation/dehydration reaction=two monomers bond together through the loss of a water molecule
Short polymer
Unlinked monomer
Dehydration removes a water
molecule, forming a new bond
H2O HO 1 2 3 4 H
Longer polymer
Hydrolysis= addition of water to separate a polymer
(reverse of dehydration reaction)
(a) Dehydration reaction in the synthesis of a polymer HO 3 H
Enzymes= proteins that speed up the reaction without being consumed in the reaction 1 2 4
Figure 5.2 The synthesis and breakdown of polymers
Hydrolysis adds a water
molecule, breaking a bond
H2O HO 1 2 3 H HO H
(b) Hydrolysis of a polymer

5. Concept 5.2: Carbohydrates serve as fuel and building material
Carbohydrates include sugars and the polymers of sugars
Ratios: 1 carbon: 2 hydrogen: 1 oxygen
Monosaccharides=single sugars (glucose (C6H12O6) , fructose, galactose)
Polysaccharides=polymers composed of many single (monomer) sugar building blocks (starch, glycogen, cellulose)
Have storage and structural roles
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6. Aldoses Glyceraldehyde Ribose Glucose Galactose Ketoses
Fig. 5-3
Trioses (C3H6O3)
Pentoses (C5H10O5)
Hexoses (C6H12O6)
Aldoses
Glyceraldehyde
Ribose
Glucose
Galactose
Figure 5.3 The structure and classification of some monosaccharides
Ketoses
Dihydroxyacetone
Ribulose
Fructose

7. Figure 5.4 Linear and ring forms of glucose
(a) Linear and ring forms
Figure 5.4 Linear and ring forms of glucose
(b) Abbreviated ring structure
Figure 5.4 Linear and ring forms of glucose

8. (a) Dehydration reaction in the synthesis of maltose
Fig. 5-5
A disaccharide is formed when a dehydration reaction joins two monosaccharides . This bond is called a glycosidic linkage
1–4
glycosidic
linkage
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
1–2
glycosidic
linkage
Figure 5.5 Examples of disaccharide synthesis
Glucose
Fructose
Sucrose
(b) Dehydration reaction in the synthesis of sucrose

9. Energy storage polysaccharides of plants and animals
Fig. 5-6
Energy storage polysaccharides of plants and animals
Chloroplast
Starch
Mitochondria
Glycogen granules
0.5 µm
1 µm
Figure 5.6 Storage polysaccharides of plants and animals
Amylose
Glycogen
Amylopectin
Starch: a plant polysaccharide
made of glucose monomers- stored
In chloroplasts and plastids
(b) Glycogen: an animal polysaccharide.
Stored in the liver and muscle cells in
humans

10. Fig. 5-7
The polysaccharide cellulose is a major component of the tough wall of plant cells
(a)  and  glucose
ring structures
 Glucose
 Glucose
Figure 5.7 Starch and cellulose structures
(b) Starch: 1–4 linkage of  glucose monomers
(b) Cellulose: 1–4 linkage of  glucose monomers
Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ
The difference is based on two ring forms for glucose: alpha () and beta ()

11. Cell walls Cellulose microfibrils in a plant cell wall Microfibril
Fig. 5-8
Cell walls
Cellulose
microfibrils
in a plant
cell wall
Microfibril
10 µm
0.5 µm
Cellulose
molecules
Figure 5.8 The arrangement of cellulose in plant cell walls
Glucose
monomer

12. Some microbes use enzymes to digest cellulose. Herbivores,
Enzymes that digest starch by hydrolyzing  linkages can’t hydrolyze  linkages in cellulose
Cellulose in human food passes through the digestive tract as insoluble fiber
Some microbes use enzymes to digest
cellulose. Herbivores,
from cows to termites, have
symbiotic relationships with
these microbes
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13. Fig. 5-10
Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods and cell walls of fungi
(a)
The structure
of the chitin
monomer.
(b)
Chitin forms the
exoskeleton of
arthropods.
(c)
Chitin is used to make
a strong and flexible
surgical thread.
Figure 5.10 Chitin, a structural polysaccharide

14. 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
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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15. Fats
Fats are constructed from two types of smaller molecules: 1 glycerol and 3 fatty acids (triacylglycerol or triglyceride)
Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats
A fatty acid consists of a carboxyl group attached to a long hydrocarbon chain. These are nonpolar and hydrophobic
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16. 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)

17. Animal fats/solid at room temperature
Fig. 5-12
Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds.
Animal fats/solid at room temperature
Unsaturated fatty acids have one or more double bonds. Plant/fish fats/liquid at room temperature
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

18. 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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19. The major function of fats is energy storage
Store 2x’s as many calories/gram as carbohydrates
Fats also function in protection of vital organs and insulation
Humans and other mammals store their fat in adipose cells
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20. Fig. 5-13
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
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

21. Phospholipids are the major component of all cell membranes
Fig. 5-14
Figure 5.14 Bilayer structure formed by self-assembly of phospholipids in an aqueous environment
Hydrophilic
head
WATER
Figure 5.14 Bilayer structure formed by self-assembly of phospholipids in an aqueous environment
Hydrophobic
tail
WATER
Phospholipids are the major component of all cell membranes

22. 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
Estrogen and testosterone are steroid hormones
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

23. Table 5-1
Concept 5.4: Proteins have many structures, resulting in a wide range of functions
Table 5-1
Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances

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
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25. Figure 5.16 The catalytic cycle of an enzyme Substrate (sucrose)
Glucose
Enzyme
(sucrase) OH
H2O
Fructose
Figure 5.16 The catalytic cycle of an enzyme H O

26.  carbon Amino Carboxyl group group
Fig. 5-UN1
 carbon
Amino
group
Carboxyl
group
Amino acids are organic molecules with carboxyl and amino groups. Amino acids differ in their properties due to differing R groups

27. 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)

28. Amino acids are linked by peptide bonds
Fig. 5-18
Amino acids are linked by peptide bonds
A polypeptide is a polymer of amino acids
Peptide
bond
(a)
Side chains
Peptide
bond
Figure 5.18 Making a polypeptide chain
Backbone
Amino end
(N-terminus)
Carboxyl end
(C-terminus)
(b)

29. A ribbon model of lysozyme A space-filling model of lysozyme
Fig. 5-19
A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape
Groove
Groove
Figure 5.19 Structure of a protein, the enzyme lysozyme
(a)
A ribbon model of lysozyme
(b)
A space-filling model of lysozyme

30. A protein’s structure determines its function
The sequence of amino acids determines a protein’s three-dimensional structure
A protein’s structure determines its function
Antibody protein
Protein from flu virus
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31. Four Levels of Protein Structure
The primary structure of a protein is its unique sequence of amino acids
Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain
Tertiary structure is determined by interactions among various side chains (R groups)
Quaternary structure results when a protein consists of multiple polypeptide chains
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32. Figure 5.21 Levels of protein structure—primary structure
Secondary
Structure
Tertiary
Structure
Quaternary
Structure
 pleated sheet
+H3N
Amino end
Examples of
amino acid
subunits
 helix
Figure 5.21 Levels of protein structure—primary structure

33. Fig. 5-21a
Primary Structure
Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word
Primary structure is determined by inherited genetic information 1 5
+H3N
Amino end 10
Amino acid
subunits 15
Figure 5.21 Levels of protein structure—primary structure 20 25

34. Secondary Structure  pleated sheet Examples of amino acid subunits
Fig. 5-21c
Secondary Structure
 pleated sheet
Examples of
amino acid
subunits
 helix
Figure 5.21 Levels of protein structure—secondary structure
The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone
Typical secondary structures are a coil called an  helix and a folded structure called a  pleated sheet

35. Tertiary structure is determined by interactions between R groups, rather than interactions between backbone constituents
These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions
Strong covalent bonds called disulfide bridges may reinforce the protein’s structure
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36. Tertiary Structure Quaternary Structure
Fig. 5-21e
Tertiary Structure
Quaternary Structure
Tertiary structure is determined by interactions between R groups., (including: hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions).
Strong covalent bonds called disulfide bridges may reinforce the protein’s structure
Quaternary structure -two or more polypeptide chains form one macromolecule
Examples: Collagen has three polypeptides coiled like a rope
Hemoglobin has four polypeptides
Figure 5.21 Levels of protein structure—tertiary and quaternary structures

37. Fig. 5-21f
Hydrophobic
interactions and
van der Waals
interactions
Polypeptide
backbone
Hydrogen
bond
Disulfide bridge
Figure 5.21 Levels of protein structure—tertiary and quaternary structures
Ionic bond
Figure 5.21 Levels of protein structure—tertiary and quaternary structures

38. Fig. 5-21g
Polypeptide
chain
 Chains
Iron
Figure 5.21 Levels of protein structure—tertiary and quaternary structures
Heme
 Chains
Hemoglobin
Collagen
Figure 5.21 Levels of protein structure—tertiary and quaternary structures

39. http://www.youtube.com/watch?v=swEc_sU Vz5I
UYQ

40. Sickle-Cell Disease: A Change in Primary Structure
A slight change in primary structure can affect a protein’s structure and ability to function
Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin
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41. Fig. 5-22
Normal hemoglobin
Sickle-cell hemoglobin
Primary
structure
Primary
structure
Val
His
Leu
Thr
Pro
Glu
Glu
Val
His
Leu
Thr
Pro
Val
Glu 1 2 3 4 5 6 7 1 2 3 4 5 6 7
Exposed
hydrophobic
region
Secondary
and tertiary
structures
Secondary
and tertiary
structures
 subunit
 subunit    
Quaternary
structure
Normal
hemoglobin
(top view)
Quaternary
structure
Sickle-cell
hemoglobin    
Function
Molecules do
not associate
with one
another; each
carries oxygen.
Function
Molecules
interact with
one another and
crystallize into
a fiber; capacity
to carry oxygen
is greatly reduced.
Figure 5.22 A single amino acid substitution in a protein causes sickle-cell disease
10 µm
10 µm
Red blood
cell shape
Normal red blood
cells are full of
individual
hemoglobin
moledules, each
carrying oxygen.
Red blood
cell shape
Fibers of abnormal
hemoglobin deform
red blood cell into
sickle shape.

42. A denatured protein is biologically inactive
Fig. 5-23
A denatured protein is biologically inactive
Denaturation
Figure 5.23 Denaturation and renaturation of a protein
Normal protein
Denatured protein
Renaturation
The loss of a protein’s native structure is called denaturation
Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel

43. Fig. 5-24
Chaperonins are protein molecules that assist the proper folding of other proteins
Correctly
folded
protein
Polypeptide
Cap
Hollow
cylinder
Chaperonin
(fully assembled)
Steps of Chaperonin
Action: 2
The cap attaches, causing the
cylinder to change shape in
such a way that it creates a
hydrophilic environment for
the folding of the polypeptide. 3
The cap comes
off, and the properly
folded protein is
released.
Figure 5.24 A chaperonin in action 1
An unfolded poly-
peptide enters the
cylinder from one end.

44. Concept 5.5: Nucleic acids store and transmit hereditary information
The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene
Genes are made of DNA, a nucleic acid
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45. The Roles of Nucleic Acids
There are two types of nucleic acids:
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
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46. The Structure of Nucleic Acids
Nucleic acids are polymers
Polymer= polynucleotides
Monomer= nucleotides
Each nucleotide consists of:
nitrogenous base
pentose sugar
phosphate group
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47. (a) Polynucleotide, or nucleic acid (c) Nucleoside components: sugars
Fig. 5-27
In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose
5 end
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous
base
Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)
Purines
Phosphate
group
Sugar
(pentose)
5C
Adenine (A)
Guanine (G)
3C
(b) Nucleotide
Sugars
3 end
Figure 5.27 Components of nucleic acids
(a) Polynucleotide, or nucleic acid
Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring
Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring
Deoxyribose (in DNA)
Ribose (in RNA)
(c) Nucleoside components: sugars

48. Nucleotide Polymers
Nucleotides are joined by covalent bonds that form between the –OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next
These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages
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49. The DNA and RNA
A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix
One DNA molecule includes many genes
The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
RNA is single-stranded
The nitrogenous bases in RNA pair up and form hydrogen bonds: adenine (A) always with uracil (U), and guanine (G) always with cytosine (C)
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50. 5' end 3' end Sugar-phosphate backbones Base pair (joined by
Fig. 5-28
5' end
3' end
Sugar-phosphate
backbones
Base pair (joined by
hydrogen bonding)
Old strands
Nucleotide
about to be
added to a
new strand
3' end
Figure 5.28 The DNA double helix and its replication
5' end
New
strands
5' end
3' end
5' end
3' end

52. Fig. 5-UN2