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1
Chapter 5
The Structure and Function of
Macromolecules
2
Root Words• con- = together (condensation reaction: a
reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water)
• di- = two (disaccharide: two monosaccharides joined together )
• glyco- = sweet (glycogen: a polysaccharide sugar used to store energy in animals)
• hydro- = water; -lyse = break (hydrolysis: breaking chemical bonds by adding water)
3
More Roots• macro- = large (macromolecule: a large
molecule)• meros- = part (polymer: a chain
made from smaller organic molecules)• mono- = single; -sacchar = sugar
(monosaccharide: simplest type of sugar)poly- = many (polysaccharide: many monosaccharides joined together)
• tri- = three (triacylglycerol: three fatty acids linked to one glycerol molecule)
4
The Molecules of Life
• Overview:– Another level in the hierarchy
of biological organization is reached when small organic molecules are joined together
– Atom ---> molecule --- macromolecule
5
Macromolecules– Are large molecules composed of
smaller molecules– Are complex in their structures
Figure 5.1
6
Macromolecules
•Most macromolecules are polymers, built from monomers• Four classes of life’s organic molecules are polymers
– Carbohydrates– Lipids– Proteins– Nucleic acids
7
– Is a long molecule consisting of many similar building blocks called monomers
– Specific monomers make up each macromolecule
– E.g. amino acids are the monomers for proteins
Polymer
8
The Synthesis and Breakdown of Polymers
• Monomers form larger molecules by condensation reactions called dehydration synthesis
(a) Dehydration reaction in the synthesis of a polymer
HO H1 2 3 HO
HO H1 2 3 4
H
H2O
Short polymer Unlinked monomer
Longer polymer
Dehydration removes a watermolecule, forming a new bond
Figure 5.2A
9
The Synthesis and Breakdown of Polymers
• Polymers can disassemble by– Hydrolysis (addition of water
molecules)
(b) Hydrolysis of a polymer
HO 1 2 3 H
HO H1 2 3 4
H2O
HHO
Hydrolysis adds a watermolecule, breaking a bond
Figure 5.2B
10
• Although organisms share the same limited number of monomer types, each organism is uniquely based on the arrangement of monomers into polymers
• An immense variety of polymers can be built from a small set of monomers
11
Carbohydrates
• Serve as fuel and building material
• Include both sugars and their polymers (starch, cellulose, etc.)
12
Sugars
• Monosaccharides– Are the simplest sugars– Can be used for fuel– Can be converted into other
organic molecules– Can be combined into polymers
13
• Examples of monosaccharides
Triose sugars(C3H6O3)
Pentose sugars(C5H10O5)
Hexose sugars(C6H12O6)
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
HO C H
H C OH
H C OH
H C OH
H C OH
HO C H
HO C H
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
C OC O
H C OH
H C OH
H C OH
HO C H
H C OH
C O
H
H
H
H H H
H
H H H H
H
H H
C C C COOOO
Ald
oses
Glyceraldehyde
RiboseGlucose Galactose
Dihydroxyacetone
Ribulose
Keto
ses
FructoseFigure 5.3
14
• Monosaccharides– May be linear– Can form rings in aqueous solution
H
H C OH
HO C H
H C OH
H C OH
H C
O
C
H
1
2
3
4
5
6
H
OH
4C
6CH2OH 6CH2OH
5C
HOH
C
H OH
H
2 C
1C
H
O
H
OH
4C
5C
3 C
H
HOH
OH
H
2C
1 C
OH
H
CH2OH
H
H
OHHO
H
OH
OH
H5
3 2
4
(a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5.
OH3
O H OO
6
1
Figure 5.4
15
• Disaccharides–Consist of two monosaccharides
–Are joined by a glycosidic linkage
16
Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide.
Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose.Notice that fructose,though a hexose like glucose, forms a five-sided ring.
(a)
(b)
H
HO
H
HOH H
OH
O H
OH
CH2OH
H
HO
H
HOH
H
OH
O H
OH
CH2OH
H
O
H
HOH H
OH
O H
OH
CH2OH
H
H2O
H2O
H
H
O
H
HOH
OH
O H
CH2OH
CH2OH HO
OHH
CH2OH
HOH
H
H
HO
OHH
CH2OH
HOH H
O
O H
OHH
CH2OH
HOH H
O
HOH
CH2OH
H HO
O
CH2OH
H
H
OH
O
O
1 2
1 41– 4
glycosidiclinkage
1–2glycosidic
linkage
Glucose
Glucose Glucose
Fructose
Maltose
Sucrose
OH
H
H
Figure 5.5
17
Polysaccharides
• Polysaccharides– Are polymers of sugars– Serve many roles in organisms
18
Storage Polysaccharides
• Starch– Is a polymer
consisting entirely of glucose monomers
– Is the major storage form of glucose in plants
Chloroplast Starch
Amylose Amylopectin
1 m
(a) Starch: a plant polysaccharideFigure 5.6
19
• Glycogen– Consists of glucose monomers– Is the major storage form of glucose in
animals Mitochondria Giycogen granules
0.5 m
(b) Glycogen: an animal polysaccharide
Glycogen
Figure 5.6
20
Structural Polysaccharides
• Cellulose– Is a polymer of glucose
21
– Has different glycosidic linkages than starch
(c) Cellulose: 1– 4 linkage of glucose monomers
H O
O
CH2OH
HOH H
H
OH
OHH
H
HO
4
C
C
C
C
C
C
H
H
H
HO
OH
H
OH
OH
OH
H
O
CH2OH
HH
H
OH
OHH
H
HO
4 OH
CH2OH
O
OH
OH
HO41
O
CH2OH
O
OH
OH
O
CH2OH
O
OH
OH
CH2OH
O
OH
OH
O O
CH2OH
O
OH
OH
HO4
O1
OH
O
OH OHO
CH2OH
O
OH
O OH
O
OH
OH
(a) and glucose ring structures
(b) Starch: 1– 4 linkage of glucose monomers
1
glucose glucose
CH2OH
CH2OH
1 4 41 1
Figure 5.7 A–C
22
Plant cells
0.5 m
Cell walls
Cellulose microfibrils in a plant cell wall
Microfibril
CH2OH
CH2OH
OH
OH
OO
OHOCH2OH
O
OOH
OCH2OH OH
OH OHO
O
CH2OH
OO
OH
CH2OH
OO
OH
O
O
CH2OHOH
CH2OHOHOOH OH OH OH
O
OH OH
CH2OH
CH2OH
OHO
OH CH2OH
OO
OH CH2OH
OH
Glucose monomer
O
O
O
O
O
O
Parallel cellulose molecules areheld together by hydrogenbonds between hydroxyl
groups attached to carbonatoms 3 and 6.
About 80 cellulosemolecules associate
to form a microfibril, themain architectural unitof the plant cell wall.
A cellulose moleculeis an unbranched glucose polymer.
OH
OH
O
OOH
Cellulosemolecules
Figure 5.8
– Is a major component of the tough walls that enclose plant cells
23
• Cellulose is difficult to digest– Cows have microbes in their stomachs
to facilitate this process
Figure 5.9
24
• Chitin, another important structural polysaccharide– Is found in the exoskeleton of
arthropods– Can be used as surgical thread
(a) The structure of the chitin monomer.
O
CH2OH
OHHH OH
H
NH
CCH3
O
H
H
(b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emergingin adult form.
(c) Chitin is used to make a strong and flexible surgical
thread that decomposes after the wound or incision heals.
OH
Figure 5.10 A–C
25
Lipids
• Lipids are a diverse group of hydrophobic molecules
• Lipids– Are the one class of large biological
molecules that do not consist of polymers– Share the common trait of being
hydrophobic
26
Fats– Are constructed from two types of smaller
molecules, a single glycerol and usually three fatty acids
– Vary in the length and number and locations of double bonds they contain
27
Fats– Are constructed from two types of smaller
molecules, a single glycerol and usually three fatty acids
– Vary in the length and number and locations of double bonds they contain
28
Fats• Are constructed from two types of smaller
molecules, a single glycerol and usually three fatty acids
29
Fats• Vary in the length and number and
locations of double bonds they contain
30
• Saturated fatty acids– Have the maximum number of
hydrogen atoms possible– Have no double bonds
(a) Saturated fat and fatty acid
Stearic acid
Figure 5.12
31
• Unsaturated fatty acids– Have one or more double bonds
(b) Unsaturated fat and fatty acidcis double bondcauses bending
Oleic acid
Figure 5.12
32
• Phospholipids– Have only two fatty acids– Have a phosphate group instead of
a third fatty acid
33
• Phospholipid structure– Consists of a hydrophilic “head”
and hydrophobic “tails”CH2
O
PO O
O
CH2CHCH2
OO
C O C O
Phosphate
Glycerol
(a) Structural formula (b) Space-filling model
Fatty acids
(c) Phospholipid symbol
Hyd
rop
hob
i c t
ails
Hydrophilichead
Hydrophobictails
–
Hyd
rop
hi li c
head
CH2 Choline+
Figure 5.13
N(CH3)3
34
• The structure of phospholipids– Results in a bilayer arrangement found
in cell membranes
Hydrophilichead
WATER
WATER
Hydrophobictail
Figure 5.14
35
Steroids
• Steroids– Are lipids characterized by a carbon
skeleton consisting of four fused rings
36
• One steroid, cholesterol– Is found in cell membranes– Is a precursor for some hormones
HO
CH3
CH3
H3C CH3
CH3
Figure 5.15
37
Proteins
• Proteins have many structures, resulting in a wide range of functions
• Proteins do most of the work in cells and act as enzymes
• Proteins are made of monomers called amino acids
38
• An overview of protein functions
Table 5.1
39
• Enzymes– Are a type of protein that acts as a
catalyst, speeding up chemical reactions
Substrate(sucrose)
Enzyme (sucrase)
Glucose
OH
H O
H2O
Fructose
3 Substrate is convertedto products.
1 Active site is available for a molecule of substrate, the
reactant on which the enzyme acts.
Substrate binds toenzyme.
22
4 Products are released.Figure 5.16
40
Polypeptides
• Polypeptides– Are polymers (chains) of amino
acids
• A protein– Consists of one or more
polypeptides
41
• Amino acids– Are organic molecules possessing
both carboxyl and amino groups– Differ in their properties due to
differing side chains, called R groups
42
Twenty Amino Acids
• 20 different amino acids make up proteins
O
O–
H
H3N+ C C
O
O–
H
CH3
H3N+ C
H
C
O
O–
CH3 CH3
CH3
C C
O
O–
H
H3N+
CH
CH3
CH2
C
H
H3N+
CH3CH3
CH2
CH
C
H
H3N+
C
CH3
CH2
CH2
CH3N+
H
C
O
O–
CH2
CH3N+
H
C
O
O–
CH2
NH
H
C
O
O–
H3N+ C
CH2
H2C
H2N C
CH2
H
C
Nonpolar
Glycine (Gly) Alanine (Ala) Valine (Val) Leucine (Leu) Isoleucine (Ile)
Methionine (Met) Phenylalanine (Phe)
C
O
O–
Tryptophan (Trp) Proline (Pro)
H3C
Figure 5.17
S
O
O–
43
O–
OH
CH2
C C
H
H3N+
O
O–
H3N+
OH CH3
CH
C C
HO–
O
SH
CH2
C
H
H3N+ C
O
O–
H3N+
C C
CH2
OH
H H H
H3N+
NH2
CH2
OC
C CO
O–
NH2 O
C
CH2
CH2
C CH3N
+
O
O–
O
Polar
Electricallycharged
–O O
C
CH2
C CH3N
+
H
O
O–
O– O
C
CH2
C CH3N
+
H
O
O–
CH2
CH2
CH2
CH2
NH3+
CH2
C CH3N
+
H
O
O–
NH2
C NH2+
CH2
CH2
CH2
C CH3N
+
H
O
O–
CH2
NH+
NHCH2
C CH3N
+
H
O
O–
Serine (Ser) Threonine (Thr)Cysteine
(Cys)Tyrosine
(Tyr)Asparagine
(Asn)Glutamine
(Gln)
Acidic Basic
Aspartic acid (Asp)
Glutamic acid (Glu)
Lysine (Lys) Arginine (Arg) Histidine (His)
44
Amino Acid Polymers
• Amino acids– Are linked by peptide bonds
45
Protein Conformation and Function
• A protein’s specific conformation (shape) determines how it functions
46
Four Levels of Protein Structure
• Primary structure– Is the unique
sequence of amino acids in a polypeptide
Figure 5.20–
Amino acid
subunits
+H3NAmino
end
oCarboxyl end
oc
GlyProThrGlyThr
Gly
GluSeuLysCysProLeu
MetVal
Lys
ValLeu
AspAlaValArgGly
SerPro
Ala
Gly
lle
SerProPheHisGluHis
Ala
GluValValPheThrAla
Asn
AspSer
GlyProArg
ArgTyrThr
lleAla
Ala
Leu
LeuSer
ProTyrSerTyrSerThr
Thr
Ala
ValVal
ThrAsnProLysGlu
ThrLys
SerTyrTrpLysAlaLeu
GluLleAsp
47
O C helix
pleated sheetAmino acid
subunitsNCH
C
O
C N
H
CO H
R
C NH
C
O H
C
R
N
HH
R C
O
R
C
H
NH
C
O H
NCO
R
C
H
NH
H
C
R
C
O
C
O
C
NH
H
R
C
C
ON
HH
C
R
C
O
NH
R
C
H C
ON
HH
C
R
C
O
NH
R
C
H C
ON
HH
C
R
C
O
N H
H C R
N HO
O C N
C
RC
H O
CHR
N HO C
RC
H
N H
O CH C R
N H
CC
N
R
H
O C
H C R
N H
O C
RC
H
H
C
RN
H
CO
C
NH
R
C
H C
O
N
H
C
• Secondary structure– Is the folding or coiling of the
polypeptide into a repeating configuration
– Includes the helix and the pleated sheet
H H
Figure 5.20
48
• Tertiary structure– Is the overall three-dimensional shape
of a polypeptide– Results from interactions between
amino acids and R groups
CH2CH
OH
O
CHO
CH2
CH2 NH3+ C-O CH2
O
CH2SSCH2
CH
CH3
CH3
H3C
H3C
Hydrophobic interactions and van der Waalsinteractions Polypeptid
ebackbone
Hyrdogenbond
Ionic bond
CH2
Disulfide bridge
49
• Quaternary structure– Is the overall protein structure that
results from the aggregation of two or more polypeptide subunits
Polypeptidechain
Collagen
Chains
ChainsHemoglobin
IronHeme
50
Review of Protein Structure
+H3NAmino end
Amino acidsubunits
helix
51
Sickle-Cell Disease: A Simple Change in Primary Structure
• Sickle-cell disease– Results from a single amino
acid substitution in the protein hemoglobin
52
Fibers of abnormalhemoglobin deform cell into sickle shape.
Primary structure
Secondaryand tertiarystructures
Quaternary structure
Function
Red bloodcell shape
Hemoglobin A
Molecules donot associatewith oneanother, eachcarries oxygen.Normal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen
10 m 10 m
Primary structure
Secondaryand tertiarystructures
Quaternary structure
Function
Red bloodcell shape
Hemoglobin SMolecules interact with one another tocrystallize into a fiber, capacity to carry oxygen is greatly reduced.
subunit subunit
1 2 3 4 5 6 7 3 4 5 6 721
Normal hemoglobin
Sickle-cell hemoglobin . . .. . .
Figure 5.21
Exposed hydrophobic
region
Val ThrHis Leu Pro Glul Glu Val His Leu Thr Pro Val Glu
53
What Determines Protein Conformation?
• Protein conformation Depends on the physical and chemical conditions of the protein’s environment
• Temperature, pH, etc. affect protein structure
54
•Denaturation is when a protein unravels and loses its native conformation(shape)
Denaturation
Renaturation
Denatured protein
Normal protein
Figure 5.22
55
The Protein-Folding Problem
• Most proteins– Probably go through several
intermediate states on their way to a stable conformation
– Denaturated proteins no longer work in their unfolded condition
– Proteins may be denaturated by extreme changes in pH or temperature
56
• Chaperonins– Are protein molecules that assist in the
proper folding of other proteins
Hollowcylinder
Cap
Chaperonin(fully assembled)
Steps of ChaperoninAction: An unfolded poly- peptide enters the cylinder from one end.
The cap attaches, causing the cylinder to change shape insuch a way that it creates a hydrophilic environment for the folding of the polypeptide.
The cap comesoff, and the properlyfolded protein is released.
Correctlyfoldedprotein
Polypeptide
2
1
3
Figure 5.23
57
• X-ray crystallography– Is used to determine a protein’s three-
dimensional structure X-raydiffraction pattern
Photographic filmDiffracted X-
raysX-ray
source
X-ray
beam
CrystalNucleic acid Protein
(a) X-ray diffraction pattern(b) 3D computer modelFigure 5.24
58
Nucleic Acids
• Nucleic acids store and transmit hereditary information
• Genes– Are the units of inheritance– Program the amino acid
sequence of polypeptides– Are made of nucleotide
sequences on DNA
59
The Roles of Nucleic Acids
• There are two types of nucleic acids– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)
60
Deoxyribonucleic Acid
• DNA– Stores information for the
synthesis of specific proteins– Found in the nucleus of cells
61
DNA Functions– Directs RNA synthesis (transcription)– Directs protein synthesis through RNA
(translation)
1
2
3
Synthesis of mRNA in the nucleus
Movement of mRNA into cytoplasm
via nuclear pore
Synthesisof protein
NUCLEUSCYTOPLASM
DNA
mRNA
Ribosome
AminoacidsPolypeptide
mRNA
Figure 5.25
62
The Structure of Nucleic Acids
• Nucleic acids– Exist as polymers called
polynucleotides
(a) Polynucleotide, or nucleic acid
3’C
5’ end
5’C
3’C
5’C
3’ endOH
Figure 5.26
O
O
O
O
63
• Each polynucleotide– Consists of monomers called nucleotides– Sugar + phosphate + nitrogen base
Nitrogenousbase
Nucleoside
O
O
O
O P CH2
5’C
3’CPhosphate
group Pentosesugar
(b) NucleotideFigure 5.26
O
64
Nucleotide Monomers
• Nucleotide monomers – Are made up of
nucleotides (sugar + base) and phosphate groups
(c) Nucleoside componentsFigure 5.26
CHCH
Uracil (in RNA)U
Ribose (in RNA)
Nitrogenous bases Pyrimidines
CN
NC
OH
NH2
CHCH
OC
NH
CHHN
CO
CCH3
N
HNC
C
HO
O
CytosineC
Thymine (in DNA)T
NHC
N C
CN
C
CH
N
NH2 O
NHC
NHH
C C
N
NH
C NH2
AdenineA
GuanineG
Purines
OHOCH2
HH H
OH
H
OHOCH2
HH H
OH
H
Pentose sugars
Deoxyribose (in DNA)Ribose (in RNA)OHOH
CH
CH
Uracil (in RNA)U
4’
5”
3’OH H
2’
1’
5”
4’
3’ 2’
1’
65
Nucleotide Polymers
• Nucleotide polymers– Are made up of nucleotides linked
by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next
66
Gene
• The sequence of bases along a nucleotide polymer– Is unique for each gene
67
The DNA Double Helix
• Cellular DNA molecules– Have two polynucleotides that spiral
around an imaginary axis– Form a double helix
68
• The DNA double helix– Consists of two antiparallel nucleotide
strands3’ end
Sugar-phosphatebackbone
Base pair (joined byhydrogen bonding)
Old strands
Nucleotideabout to be added to a new strand
A
3’ end
3’ end
5’ end
Newstrands
3’ end
5’ end
5’ end
Figure 5.27
69
A,T,C,G
• The nitrogenous bases in DNA– Form hydrogen bonds in a
complementary fashion (A with T only, and C with G only)
70
DNA and Proteins as Tape Measures of Evolution
• Molecular comparisons – Help biologists sort out the
evolutionary connections among species
71
The Theme of Emergent Properties in the Chemistry of
Life: A Review
• Higher levels of organization– Result in the emergence of
new properties
• Organization– Is the key to the chemistry of
life
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