Download 3 - Moodle NTOU

CAMPBELL
BIOLOGY
TENTH
EDITION
Global
Edition
Reece • Urry • Cain • Wasserman •
Minorsky • Jackson
5
Biological
Macromolecules 黃章文
and Lipids
Chang-Wen Huang
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
Assistant Professor
[email protected]
Lab. Marine Molecular Genetics, Breeding and
Biotechnology
Department of Aquaculture, College of Life Sciences
National Taiwan Ocean University
The Molecules of Life
Overview
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.
Molecular structure and function are
inseparable.
2
Why do scientists study the
structures of macromolecules?
為何科學家們研究大分子結構？
Macromolecules are
polymers, built from
monomers
Polymers
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.
1) Carbohydrates
2) Proteins
3) Nucleic acids
© 2011 Pearson Education, Inc.
5
The Synthesis and Breakdown
of Polymers
A dehydration reaction occurs
when two monomers bond together
through the loss of a water
molecule.
Polymers are disassembled to
monomers by hydrolysis, a
reaction that is essentially the
reverse of the dehydration reaction.
© 2011 Pearson Education, Inc.
6
Dehydration reaction:
synthesizing a polymer
1
2
3
4
Unlinked
monomer
Short polymer
Dehydration removes
a water molecule.
Forming a
new bond
Longer polymer
1
2
3
4
7
Hydrolysis:
breaking down a polymer
1
2
3
4
Hydrolysis adds
a water molecule,
breaking a bond.
1
2
3
4
8
The Diversity of Polymers
Each cell has thousands of
different macromolecules.
HO
Macromolecules vary
among cells of an
organism, vary more within
a species, and vary even
more between species.
An immense (huge)
variety of polymers can
be built from a small set of
monomers.
© 2011 Pearson Education, Inc.
9
Concept Check 5.1
1. What are the four main classes of large
biological molecules? Which class does not
consist of polymers?
2. How many molecules of water are needed to
completely hydrolyze a polymer that is ten
monomers long?
3. WHAT IF? If you eat a piece of fish, what
reactions must occur for the amino acid
monomers in the protein of the fish to be
converted to new proteins in your body?
Carbohydrates serve
as fuel and building
material
Carbohydrates
Include sugars and the polymers of
sugars.
The simplest carbohydrates are
monosaccharides, or single sugars.
Carbohydrate macromolecules are
polysaccharides, polymers composed
of many sugar building blocks.
© 2011 Pearson Education, Inc.
13
Sugars (Mono-)
Monosaccharides have molecular formulas
that are usually multiples of CH2O.
Glucose (C6H12O6) is the most common
monosaccharide.
Monosaccharides are classified by
 The location of the carbonyl group (as aldose
or ketose).
 The number of carbons in the carbon skeleton.
© 2011 Pearson Education, Inc.
14
Figure 5.3
Aldoses (Aldehyde Sugars) Ketoses (Ketone Sugars)
Trioses: 3-carbon sugars (C3H6O3)
甘油酸 Glyceraldehyde
Dihydroxyacetone
二羥基丙酮
Pentoses: 5-carbon sugars (C5H10O5)
核糖
Ribose
Ribulose
核酮糖
Hexoses: 6-carbon sugars (C6H12O6)
Fructose
Glucose Galactose
Fructose
15
Figure 5.4
1
2
6
6
5
5
3
4
4
5
1
3
2
4
1
3
2
6
(a) Linear and ring forms
6
5
4
Though often drawn as linear
skeletons, in aqueous solutions
many sugars form glucose rings
(carbon 1 bonds to the oxygen
attached to carbon 5).
1
3
2
(b) Abbreviated ring structure
Monosaccharides serve as a major
fuel for cells and as raw material for
building molecules.
16
17
Maillard Reaction
受熱的過程中會產生褐色物質，讓食物具有特殊的外觀，而
且形成特殊的風味，此稱之梅納反應 (非酵素性褐化反應)。
最早由法國人梅納氏在1912年提出，影響很多食品的製造和
儲存。
包括糖與碳水化合物的焦化作用，以及碳水化合物和蛋白質
、胺基酸等加熱處理或儲存後產生的反應。這兩種化學反應
都會產生褐色的物質，通常又稱作黑色素。
例如葡萄糖單獨在攝氏180度下加熱，可以產生焦糖香氣，
如果和離胺酸一起加熱，就會發出像麵包的香氣，和纈胺酸
一起加熱，也會形成類似巧克力的香氣。若缺乏非酵素性褐
化反應，那麼這些烘焙食品的吸引力，也會受到影響。
18
Sugars (Di-)
A disaccharide is formed when a
dehydration reaction joins two
monosaccharides.
This covalent bond is called a
glycosidic linkage (糖苷鍵).
© 2011 Pearson Education, Inc.
19
Figure 5.5
1–4
glycosidic
1 linkage 4
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
1–2
glycosidic
1 linkage 2
Glucose
Fructose
Sucrose
(b) Dehydration reaction in the synthesis of sucrose
20
Sugars (Poly-)
• Polysaccharides, the polymers of sugars,
have storage and structural roles.
• The structure and function of a polysaccharide
are determined by its sugar monomers and
the positions of glycosidic linkages.
© 2011 Pearson Education, Inc.
21
Storage Polysaccharides
• Starch, a storage polysaccharide of plants,
consists entirely of glucose monomers.
• Plants store surplus starch as granules within
chloroplasts and other plastids (細胞質體).
• The simplest form of starch is amylose.
© 2011 Pearson Education, Inc.
22
Figure 5.6
Chloroplast
Starch granules
Amylopectin
Amylose
(a) Starch:
1 m
a plant polysaccharide
Mitochondria
Glycogen granules
Glycogen
(b) Glycogen:
0.5 m
an animal polysaccharide
What’s cell?
23
• Humans and other vertebrates store
glycogen mainly in liver and muscle cells.
© 2011 Pearson Education, Inc.
24
Structural Polysaccharides
• The polysaccharide cellulose is a major
component of the tough wall of plant cells.
• 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 ().
Animation: Polysaccharides
© 2011 Pearson Education, Inc.
25
Figure 5.7
(a)  and  glucose
ring structures
4
1
4
 Glucose
 Glucose
1 4
(b) Starch: 1–4 linkage of  glucose monomers
Polymers with α-glucose are
helical.
1
1 4
(c) Cellulose: 1–4 linkage of  glucose monomers
Polymers with β-glucose are
straight.
In straight structures, H atoms
on one strand can bond with OH
groups on other strands.
26
Figure 5.8
Cellulose
microfibrils in a
plant cell wall
Cell wall
Parallel cellulose molecules
held together this way are
grouped into microfibrils,
which form strong building
materials for plants.
Microfibril
10 m
0.5 m
Cellulose
molecules
 Glucose
monomer
27
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. Many
herbivores, from cows to
termites, have symbiotic
relationships with these
microbes.
© 2011 Pearson Education, Inc.
28
Chitin
Structural
polysaccharide, is
found in the
exoskeleton of
arthropods (節肢動
物).
Chitin also provides
structural support for
the cell walls of many
fungi.
29
29
Chitin
幾丁質(chitin)又稱
殼多醣、甲殼質、
甲殼素。
由N-乙醯-D-胺基葡
萄糖或D-胺基葡萄
糖以β -1,4糖苷鍵連
接而成之低聚合度
水溶性胺基多醣。
© 2011 Pearson Education, Inc.
The structure of the
chitin monomer
30
Figure 5.9b
Chitin is used to make a strong and flexible surgical
thread that decomposes after the wound or incision
heals.
31
Concept Check 5.2
1. Write the formula for a monosaccharide that
has three carbons.
2. A dehydration reaction joins two glucose
molecules to form maltose. The formula for
glucose is C6H12O6. what is the formula for
maltose?
3. WHAT IF? After a caw is given antibiotics to treat
an infection, a vet gives the animal a drink of “gut
culture” containing various prokaryotes. Why is
this necessary?
瘤胃開窗牛群在乳業先進國家早已是主要資產
乳牛每天採食18到
25公斤的乾物質，
可以生產20到40公
斤的牛乳。
乳牛的瘤胃是進行牧草纖維分解與飼糧
氮轉換的消化器官，藉由瘤胃內共生的
細菌（每毫升瘤胃液有一兆個）、原蟲（
每毫升瘤胃液有一百萬個）與真菌等微
生物所分泌的酵素，可提供牛隻所需的
脂肪酸和蛋白質量達50到65%之多。
Lipids are a diverse
group of hydrophobic
molecules
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:
(1)Fats, (2)Phospholipids, (3)Steroids.
© 2011 Pearson Education, Inc.
35
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.
© 2011 Pearson Education, Inc.
36
Figure 5.10a
hydroxyl carboxyl
group
group
Fatty acid
(in this case, palmitic acid)
Glycerol
One of three dehydration reactions in
the synthesis of a fat.
37
• 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.
© 2011 Pearson Education, Inc.
38
Figure 5.10b
Ester linkage
Fat molecule (triacylglycerol)
39
• 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
© 2011 Pearson Education, Inc.
40
Figure 5.11a
Saturated fat
Structural
formula of a
saturated fat
molecule
Space-filling
model of stearic
acid, a saturated
fatty acid
41
Figure 5.11b
Unsaturated fat
Structural
formula of an
unsaturated fat
molecule
Space-filling model
of oleic acid, an
unsaturated fatty
acid
Cis double bond
causes bending.
42
Saturated and Unsaturated
Fatty Acids
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.
© 2011 Pearson Education, Inc.
43
• 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.
© 2011 Pearson Education, Inc.
44
Certain unsaturated fatty acids are
not synthesized in the human body.
These must be supplied in the diet.
These essential fatty acids include
the omega-3 fatty acids, required
for normal growth, and thought to
provide protection against
cardiovascular disease.
© 2011 Pearson Education, Inc.
46
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.
© 2011 Pearson Education, Inc.
47
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.
© 2011 Pearson Education, Inc.
48
Hydrophobic tails
Hydrophilic head
Figure 5.12
Choline
Phosphate
Glycerol
Fatty acids
Hydrophilic
head
Hydrophobic
tails
(a) Structural formula
(b) Space-filling model
(c) Phospholipid symbol
Add to wather?
49
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.
© 2011 Pearson Education, Inc.
50
Figure 5.13
Bilayer structure formed by selfassembly of phospholipids in an
aqueous environment
Hydrophilic
head
Hydrophobic
tail
WATER
WATER
51
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.
© 2011 Pearson Education, Inc.
52
Figure 5.14
Cholesterol, a steroid
Cholesterol is the molecule from which other steroids,
including the sex hormones, are synthesized.
Steroids vary in the chemical groups attached to
their four interconnected rings (shown in gold).
53
Concept Check 5.3
1. Compare the structure of a fat (triglyceride)
with that of a phospholipid?
2. Why are human sex hormones considered
lipids?
3. WHAT IF? Suppose a membrane surrounded an
oil droplet, as it does in the cells of plant seeds
and in some animal cells. Describe and explain
the form it might take.
Proteins include a
diversity of
structures, resulting
in a wide range of
functions
Concept 5.4: Proteins include a diversity of
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.
© 2011 Pearson Education, Inc.
56
Figure 5.15a
Enzymatic proteins
Function: Selective acceleration of chemical reactions
Example: Digestive enzymes catalyze the hydrolysis
of bonds in food molecules.
Enzyme
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.
57
Figure 5.15h
Structural proteins
Function: Support
Examples: Keratin is the protein of hair, horns,
feathers, and other skin appendages. Insects and
spiders use silk fibers to make their cocoons and webs,
respectively. Collagen and elastin proteins provide a
fibrous framework in animal connective tissues.
Collagen
Connective
tissue
60 m
58
Figure 5.15b
Storage proteins
Function: Storage of amino acids
Examples: Casein, the protein of milk, is the major
source of amino acids for baby mammals. Plants have
storage proteins in their seeds. Ovalbumin is the
protein of egg white, used as an amino acid source
for the developing embryo.
Ovalbumin
Amino acids
for embryo
59
Figure 5.15f
Transport proteins
Function: Transport of substances
Examples: Hemoglobin, the iron-containing protein of
vertebrate blood, transports oxygen from the lungs to
other parts of the body. Other proteins transport
molecules across cell membranes.
Transport
protein
Cell membrane
60
Figure 5.15c
Hormonal proteins
Function: Coordination of an organism’s activities
Example: Insulin, a hormone secreted by the
pancreas, causes other tissues to take up glucose,
thus regulating blood sugar concentration.
High
blood sugar
Insulin
secreted
Normal
blood sugar
61
Figure 5.15g
Receptor proteins
Function: Response of cell to chemical stimuli
Example: Receptors built into the membrane of a
nerve cell detect signaling molecules released by
other nerve cells.
Signaling
molecules
Receptor
protein
62
Figure 5.15d
Contractile and motor proteins
Function: Movement
Examples: Motor proteins are responsible for the
undulations of cilia and flagella. Actin and myosin
proteins are responsible for the contraction of
muscles.
Actin
Muscle tissue
Myosin
100 m
63
Figure 5.15e
Defensive proteins
Function: Protection against disease
Example: Antibodies inactivate and help destroy
viruses and bacteria.
Antibodies
Virus
Bacterium
64
Polypeptides
Polypeptides are unbranched
polymers built from the same set
of 20 amino acids.
A protein is a biologically
functional molecule that consists
of one or more polypeptides.
© 2011 Pearson Education, Inc.
65
Amino Acid Monomers
Side chain (R group)
• Amino acids are organic
molecules with carboxyl
and amino groups.
• Amino acids differ in their
properties due to differing
side chains, called R
groups.
© 2011 Pearson Education, Inc.
 carbon
Amino
group
Carboxyl
group
66
Figure 5.16a
Nonpolar side chains; hydrophobic
Side chain
Glycine
(Gly or G)
Methionine
(Met or M)
Alanine
(Ala or A)
Valine
(Val or V)
Phenylalanine
(Phe or F)
Leucine
(Leu or L)
Tryptophan
(Trp or W)
Isoleucine
(Ile or I)
Proline
(Pro or P)
67
Figure 5.16b
Polar side chains; hydrophilic
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Glutamine
(Gln or Q)
68
Figure 5.16c
Electrically charged side chains; hydrophilic
Basic (positively charged)
Acidic (negatively charged)
Aspartic acid Glutamic acid
(Glu or E)
(Asp or D)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
69
Amino Acid Polymers
• Amino acids are linked by peptide bonds.
• A polypeptide is a polymer of amino acids.
• Polypeptides range in length from a few to
more than a thousand monomers.
• Each polypeptide has a unique linear
sequence of amino acids, with a carboxyl
end (C-terminus) and an amino end (Nterminus).
© 2011 Pearson Education, Inc.
70
Figure 5.17
Peptide bond
New peptide
bond forming
Side
chains
Backbone
Amino end
(N-terminus)
Peptide
bond
Carboxyl end
(C-terminus)
71
Protein Structure and Function
• A functional protein consists of one or
more polypeptides precisely twisted,
folded, and coiled into a unique shape.
© 2011 Pearson Education, Inc.
72
Structure of a protein, the
enzyme lysozyme
Groove
(a) A ribbon model
Groove
(b) A space-filling model
73
溶菌酶（Lysozyme）
分子量為14.4kDa的酵素，能夠催化肽聚糖
中N-乙醯胞壁酸和N-乙醯氨基葡萄糖殘基
間和殼糊精中N-乙醯葡糖胺殘基間的1,4-β
鏈的水解，而破壞細菌的細胞壁。
溶菌酶存在人體中之細胞分泌液，如唾液
、眼淚及其他一些體液中，也存在於粒線
體中的細胞質顆粒體中。蛋白中也有大量
的溶菌酶。
74
• The sequence of amino acids determines a
protein’s three-dimensional structure.
• A protein’s structure determines its function.
© 2011 Pearson Education, Inc.
75
Figure 5.19
An antibody binding to a
protein from a flu virus
Antibody protein
Protein from flu virus
76
Four Levels of Protein Structure
• 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.
© 2011 Pearson Education, Inc.
77
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.
Animation: Primary Protein Structure
© 2011 Pearson Education, Inc.
78
Figure 5.20a
Primary structure
Amino
acids
Amino end
Primary structure of transthyretin
Carboxyl end
79
Secondary structure
The coils and folds of secondary
structure result from hydrogen bonds
between repeating constituents of the
polypeptide backbone.
Typical secondary structures are:
1) A coil called an  helix.
2) A folded structure called a  pleated sheet.
Animation: Secondary Protein Structure
© 2011 Pearson Education, Inc.
80
Figure 5.20c
Secondary structure
 helix
 pleated sheet
Hydrogen bond
 strand, shown as a flat
arrow pointing toward
the carboxyl end
Hydrogen bond
81
Figure 5.20d
Spiders secrete silk fibers made of a structural
protein containing β pleated sheets, which
allow the spider web to stretch and recoil
82
82
Tertiary structure
Tertiary structure is determined by interactions
between R groups.
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.
Animation: Tertiary Protein Structure
© 2011 Pearson Education, Inc.
83
Figure 5.20f
Tertiary structure
Transthyretin (TTR) polypeptide
Hydrogen
bond
Hydrophobic
interactions and
van der Waals
interactions
Disulfide
bridge
Ionic bond
Polypeptide
backbone
84
Quaternary structure
When two or more
polypeptide chains
form one
macromolecule.
Transthyretin protein
(four identical polypeptides)
Animation: Quaternary Protein Structure
© 2011 Pearson Education, Inc.
85
Figure 5.20b
Tertiary
structure
Secondary
structure
Quaternary
structure
 helix
Hydrogen bond
 pleated sheet
 strand
Hydrogen
bond
Transthyretin
polypeptide
Transthyretin
protein
86
The complete protein
Collagen is a fibrous protein
consisting of three polypeptides coiled
like a rope.
Hemoglobin is a globular protein
consisting of four polypeptides: two
alpha and two beta chains.
© 2011 Pearson Education, Inc.
87
Figure 5.20h
Collagen
Journal of Structural Biology 142 (2003) 327–333
88
89
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.
© 2011 Pearson Education, Inc.
90
Figure 5.21
Sickle-cell hemoglobin
Normal hemoglobin
Primary
Structure
1
2
3
4
5
6
7
Secondary
and Tertiary
Structures
Quaternary
Structure
Function
Molecules do not
associate with one
another; each carries
oxygen.
Normal
hemoglobin
 subunit

Red Blood
Cell Shape

10 m


1
2
3
4
5
6
7
Exposed
hydrophobic
region
Sickle-cell
hemoglobin

 subunit

Molecules crystallize
into a fiber; capacity
to carry oxygen is
reduced.

10 m

91
What Determines Protein Structure?
• In addition to primary structure, physical
and chemical conditions can affect
structure.
• Alterations in pH, salt concentration,
temperature, or other environmental
factors can cause a protein to unravel.
• This loss of a protein’s native structure is
called denaturation.
• A denatured protein is biologically inactive.
© 2011 Pearson Education, Inc.
92
Figure 5.22
tu
Normal protein
Denatured protein
93
Protein Folding in the Cell
• It is hard to predict a protein’s structure
from its primary structure.
• Most proteins probably go through several
stages on their way to a stable structure.
• Chaperonins are protein molecules that
assist the proper folding of other proteins.
• Diseases such as Alzheimer’s, Parkinson’s,
and mad cow disease are associated with
misfolded proteins.
© 2011 Pearson Education, Inc.
94
Figure 5.23b
Polypeptide
Correctly
folded
protein
Steps of Chaperonin 2 The cap attaches, causing 3 The cap comes
Action:
the cylinder to change
off, and the
1 An unfolded polyshape in such a way that
properly folded
peptide enters the
it creates a hydrophilic
protein is
cylinder from
environment for the
released.
one end.
folding of the polypeptide.
95
To determine and predict
a protein’s structure
X-ray crystallography
Nuclear magnetic resonance
(NMR) spectroscopy (does not
require protein crystallization)
Bioinformatics uses computer
programs (from amino acid
sequences)
© 2011 Pearson Education, Inc.
96
Figure 5.24a
What can the 3-D shape of the enzyme RNA
polymerase II tell us about its function?
EXPERIMENT
Diffracted
X-rays
X-ray
source X-ray
beam
Crystal
Digital detector X-ray diffraction
pattern
Roger Kornberg利用X光結晶繪圖學技
術確立第II型RNA聚合酶的立體形狀。
Roger Kornberg
(Nobel Prize in Chemistry, 2006)
使所有三種成分的複合體結晶化之後，瞄準穿過
結晶體的X光束，結晶體的諸原子使X光繞射成排
列整齊的陣列。數位偵測器將此記錄成為「X光
繞射圖形」的點狀圖案。
97
Figure 5.24b
RESULTS
RNA
DNA
RNA
polymerase II
運用自X光繞射圖形的數據，以及化學方法所定出的
胺基酸序列，Roger Kornberg及其同事在電腦軟體的
輔助協助下，建構了該複合體的立體模型。
98
Concept Check 5.4
1. What parts of a polypeptide participate in the
bonds that hold together secondary structure?
Tertiary structure?
2. Thus far in the chapter, the Greed letters α and β
have been used to specify at least three different
pairs of structures. Name and briefly describe
them.
3. WHAT IF? Where would you expect a
polypeptide region rich in the amino acids valine,
leucine, and isoleucine to be located in a folded
polypeptide? Explain.
Nucleic acids store,
transmit, and help
express hereditary
information
Concept 5.5: Nucleic acids store, transmit,
and help express 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 made of monomers called
nucleotides.
© 2011 Pearson Education, Inc.
101
The Roles of Nucleic Acids
• There are two types of nucleic acids
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
• DNA provides directions for its own
replication.
• DNA directs synthesis of messenger
RNA (mRNA) and, through mRNA,
controls protein synthesis.
• Protein synthesis occurs in ribosomes.
© 2011 Pearson Education, Inc.
102
Figure 5.25-3
DNA
1 Synthesis of
mRNA
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into
cytoplasm
Ribosome
3 Synthesis
of protein
Polypeptide
Amino
acids
103
The Components of Nucleic Acids
• Nucleic acids are polymers called
polynucleotides.
• Each polynucleotide is made of monomers
called nucleotides.
• Each nucleotide consists of a nitrogenous
base, a pentose sugar, and one or more
phosphate groups.
• The portion of a nucleotide without the
phosphate group is called a nucleoside.
© 2011 Pearson Education, Inc.
104
Figure 5.26
5 end
Sugar-phosphate backbone
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous
base
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Purines
5C
1C
5C
3C
Phosphate
group
3C
Sugar
(pentose)
Guanine (G)
Adenine (A)
(b) Nucleotide
Sugars
3 end
(a) Polynucleotide, or nucleic acid
Deoxyribose (in DNA)
Ribose (in RNA)
(c) Nucleoside components
105
• Nucleoside = nitrogenous base + sugar
• There are two families of nitrogenous bases
– Pyrimidines (cytosine, thymine, and uracil)
have a single six-membered ring.
– Purines (adenine and guanine) have a sixmembered ring fused to a five-membered ring.
• In DNA, the sugar is deoxyribose; in RNA, the
sugar is ribose.
• Nucleotide = nucleoside + phosphate group
© 2011 Pearson Education, Inc.
106
Nucleotide Polymers
• Nucleotide polymers are linked together to build
a polynucleotide.
• Adjacent 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 sugarphosphate units with nitrogenous bases as
appendages.
• The sequence of bases along a DNA or mRNA
polymer is unique for each gene.
© 2011 Pearson Education, Inc.
107
The Structures of DNA and RNA Molecules
• RNA molecules usually exist as single
polypeptide chains.
• DNA molecules have two polynucleotides
spiraling around an imaginary axis, forming a
double helix.
• In the DNA double helix, the two backbones run
in opposite 5→ 3 directions from each other, an
arrangement referred to as antiparallel.
• One DNA molecule includes many genes.
© 2011 Pearson Education, Inc.
108
• The nitrogenous bases in DNA pair up and form
hydrogen bonds: adenine (A) always with
thymine (T), and guanine (G) always with
cytosine (C).
• Called complementary base pairing.
• Complementary pairing can also occur between
two RNA molecules or between parts of the same
molecule.
• In RNA, thymine is replaced by uracil (U) so A
and U pair.
© 2011 Pearson Education, Inc.
109
Figure 5.27
5
3
Sugar-phosphate
backbones
Hydrogen bonds
Base pair joined
by hydrogen
bonding
3
5
(a) DNA
Base pair joined
by hydrogen bonding
(b) Transfer RNA
110
DNA and Proteins as Tape Measures of
Evolution
• The linear sequences of nucleotides in
DNA molecules are passed from parents to
offspring.
• Two closely related species are more
similar in DNA than are more distantly
related species.
• Molecular biology can be used to assess
evolutionary kinship.
© 2011 Pearson Education, Inc.
111
Concept Check 5.5
1. DRAW IT Go to Figure 5.24a and, for the top
three nucleotides, number all the carbons in the
sugars, circle the nitrogenous bases, and star
the phosphates.
2. DRAW IT In a DNA double helix, a region along
one DNA strand has this sequence of
nitrogenous bases: 5’-TAGGCCT-3’. Copy this
sequence, and write down its complementary
strand, clearly indicating the 5’ and 3’ ends of the
complementary strand.
Genomics and
proteomics have
transformed
biological inquiry
and applications
Concept 5.6:
Genomics and proteomics have transformed
biological inquiry and applications
Once the structure of DNA and its
relationship to amino acid sequence was
understood, biologists sought to “decode”
genes by learning their base sequences.
The first chemical techniques for DNA
sequencing were developed in the 1970s
and refined over the next 20 years.
114
It is enlightening to sequence the full
complement of DNA in an organism’s
genome.
The rapid development of faster and less
expensive methods of sequencing was a
side effect of the Human Genome Project.
Many genomes have been sequenced,
generating reams of data.
Bioinformatics uses computer software
and other computational tools to deal with
the data resulting from sequencing many
genomes.
Analyzing large sets of genes or even
comparing whole genomes of different
species is called genomics.
A similar analysis of large sets of proteins
including their sequences is called
proteomics
MAKE CONNECTIONS
Contributions of Genomics and
Proteomics to Biology
Paleontology
Evolution
Hippopotamus
Medical Science
Short-finned pilot whale
Conservation Biology
Species
Interactions
118
DNA and Proteins as Tape
Measures of Evolution
Sequences of genes and their protein products
document the hereditary background of an
organism.
Linear sequences of DNA molecules are passed
from parents to offspring.
We can extend the concept of “molecular
genealogy” to relationships between species.
Molecular biology has added a new measure to the
toolkit of evolutionary biology.
119
Skills exercise
Analyzing polypeptide sequence data
► Human
(人類)
► Rhesus
monkey
(恆河猴)
► Gibbon
(長臂猿)
120
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.
© 2011 Pearson Education, Inc.
121
Welcome! Questions?
Egg and Life
雞蛋，
從外打破是食物，
從内打破是生命。
人生，
從外打破是壓力，
從内打破是成長。
生物學期中考試公告
班級：水產養殖學系1A, 1B
日期：104年11月4日（三）
時間：18:30~20:00
人數：人
地點：群海廳CLS108
 攜帶學分證。
 座位分配（亂數逢機）。
103.10.03
天生比較聰明的學生
，基測卻考得比較差
，這是怎麼回事？
2013年02月08日
125
台灣研究學者針對779位的高中生
抽血採樣做分析，將被認為智商比
較高（認知能力好）的人，和智商
較低的人相比，後一群學生的平均
分數反而高8%，尤其是自然學科
更明顯，怎麼天生聰明的人，基測
反而考不好呢？
126
IQ高, 基測失常
智商高，認知佳
表現失靈
壓力
N=779
智商&認知普通
表現佳
127
多巴胺（Dopamine）
C6H3(OH)2-CH2-CH2-NH2
一種腦內分泌物，屬於神經傳導
物質，可影響一個人的情緒。
改變放電速度，增加大腦運作。
128
關鍵的COMT基因
COMT基因
緩慢移除多巴胺
快速清除多巴胺
129