Transcript c - kyoussef-mci

Macromolecules
– Are large molecules composed of a large number
of repeated subunits
– Are complex in their structures
Figure 5.1
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Macromolecules
Macromolecule
Subunit
Complex Carbohydrates
(e.g. starch)
Simple sugar (e.g.
glucose)
Lipid (triglycerides)
Glycerol and fatty acids
Protein
Amino Acids
Nucleic Acids (DNA or RNA)
Nucleotides
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• A polymer
– Is a long molecule consisting of many
similar smaller building blocks called
monomers
– Specific monomers make up each
macromolecule
– E.g. amino acids are the monomers for
proteins
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The Synthesis and Breakdown of
Macromolecules
• Monomers form larger molecules by condensation
reactions called dehydration synthesis
HO
1
2
3
H
Unlinked monomer
Short polymer
Dehydration removes a water
molecule, forming a new bond
HO
1
2
H
HO
3
H 2O
4
H
Longer polymer
Figure 5.2A (a) Dehydration reaction in the synthesis of a polymer
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Condensation Reactions
• Requires energy because new bonds
are being formed
• Are also called a anabolic reactions
because smaller molecules join
together to form larger molecules
small  LARGE
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The Synthesis and Breakdown of
Macromolecules
• Polymers can disassemble by
– Hydrolysis (addition of water molecules to lyse or
“break apart” the macromolecule)
HO
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
1
2
3
H
Figure 5.2B (b) Hydrolysis of a polymer
H
H 2O
HO
H
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Hydrolysis
• Releases energy because bonds are
being broken
• Are also called a Catabolic reactions
because larger molecules are being
broken down into smaller subunits
LARGE  small
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• An immense variety of polymers
can be built from a small set of
monomers
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Question 1
• How many molecules of water are needed to
completely hydrolyze a polymer that is 10
monomers long?
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Question 2
• After you eat a slice of apple, which reactions
must occur for the amino acid monomers in
the protein of the apple to be converted into
proteins in your body?
Amino acids are incorporated into proteins in
your body by dehydration reactions
CARBOHYDRATES
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Carbohydrates
• Serve as fuel and building
material
• Include both sugars and their
polymers (starch, cellulose, etc.)
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Sugars
• Monosaccharides
– Are the simplest sugars
– Contain a single chain of carbon atoms
with hydroxyl groups
– They also contain carbonyl (aldehyde
or keytone) groups
– Can be combined into polymers
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• Examples of monosaccharides
Triose sugars
(C3H6O3)
H
O
Aldoses
C
Pentose sugars
(C5H10O5)
H
O
C
H
O
C
O
C
C OH
H C OH
H
C OH
H C OH
H
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
H C OH
H
Ribose
H
Ketoses
H
H
Glyceraldehyde
H
H C OH
H C OH
HO C H
HO C H
HO C H
H
H
Glucose
Galactose
H
H C OH
H C OH
H C OH
C O
C O
C O
H C OH
H C OH
HO C H
H
H C OH
H C OH
Dihydroxyacetone
H C OH
H C OH
H
Ribulose
Figure 5.3
Hexose sugars
(C6H12O6)
H C OH
H
Fructose
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• Monosaccharides
– May be linear
– Can form rings
O
H
1C
H
HO
2
3
C
6CH OH
2
OH
H
C
H
4
H
H
H
C
C
C
H
OH
4C
OH
OH
OH
5C
H
O
H
OH
5
6
5C
6CH OH
2
3
C
H
2C
O
H
H
4C
1C
CH2OH
O
OH
H
OH
3C
6
H
1C
H
2C
4
OH
H
H
H
OH
HO
3
1
OH
2
OH
H
H
O
5
OH
OH
H
Figure 5.4 (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.
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α glucose vs. β glucose
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• Oligosaccharides – contain two or three
monosaccarides attached by covalent
bonds called glycosidic linkages
– Disaccharides
• Consist of two monosaccharides
• Are joined by a single glycosidic linkage
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(a)
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.
CH2OH
CH2OH
H
O
H
OH
H
OH
HO
H
H
H
HO
O
H
OH
H
H
OH
CH2OH
H
OH
OH
O
H
H
OH
CH2OH
H
1
H
HO
O
H
4
H
OH
H
H
OH
O
H
OH
1–4
glycosidic
linkage
H
OH
OH
H2O
Glucose
Glucose
CH2OH
H
(b) Dehydration reaction
HO
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.
O
H
OH
H
H
CH2OH
H
OH
HO
H
CH2OH
O
H
H
O
H
H
OH
HO
CH2OH
OH
OH
Maltose
H
CH2OH
1–2
glycosidic
1
linkage
O
H
H
2
H
HO
O
HO
H
OH
CH2OH
OH
H
H2O
Glucose
Fructose
Sucrose
Figure 5.5
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Polysaccharides
• Polysaccharides
– Are polymers of sugars with several hundred to
several thousand monosaccharide subunits held
together by glycosidic linkages
– Serve many roles in organisms
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Storage Polysaccharides
Chloroplast
Starch
• Starch
– Is a polymer
consisting entirely
of glucose
monomers
– Is the major
storage form of
glucose in plants
1 m
Amylose
Figure 5.6
Amylopectin
(a) Starch: a plant polysaccharide
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Two types of Starch
• Amylose
– Straight chain polymer of α (alpha) glucose
– Has 1-4 glycosidic linkages
• Amylopectin
– Branched chains of α glucose and β glucose
– Has 1-4 glycosidic linkages in the main chains and
1-6 glycosidic linkages at the branch points
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Glucose Storage in Animals
• Glycogen
– Consists of glucose monomers
– Similar to Amylopectin (has 1-4 and 1-6
glycosidic linkages), but there are more
branches in glycogen
– Stored in muscle and liver
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Mitochondria
Giycogen granules
0.5 m
Glycogen
Figure 5.6
(b) Glycogen: an animal polysaccharide
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Structural Polysaccharides
• Cellulose
– Is a polymer of glucose
– Has different glycosidic linkages than starch
– The main structural polysaccharide in plants and plant cell
walls
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– Cellulose is a straight chain polymer of β glucose with
1-4 glycosidic linkages
H
O
C
CH2OH
H
4
H
OH
O
H
H
OH
HO
H
OH
 glucose
H
C
OH
HO
C
H
CH2OH
O
H
OH H
H
4
H
C
OH
H
C
OH
H
C
OH
HO
OH
1
H
H
OH
 glucose
(a)  and  glucose ring structures
CH2OH
CH2OH
O
HO
O
4
1
OH
O
1
OH
O
4
O
1
OH
OH
OH
CH2OH
CH2OH
O
O
4
1
OH
O
OH
OH
(b) Starch: 1– 4 linkage of  glucose monomers
CH2OH
O
HO
Figure 5.7 A–C
OH
OH
O
1
4
OH
OH
CH2OH
O
O
OH
O
O
CH2OH
OH
OH
(c) Cellulose: 1– 4 linkage of  glucose monomers
OH
O
CH2OH
OH
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– Unlike amylose and amylopectin (starches),
cellulose molecules are neither coiled nor
branched
Cellulose microfibrils
in a plant cell wall
Cell walls
Microfibril
About 80 cellulose
molecules associate
to form a microfibril, the
main architectural unit
of the plant cell wall.
0.5 m
Plant cells
OH CH2OH
CH2OH
O O
O O
OH
OH
OH
O
O O
OH
OH CH2OH
Parallel cellulose molecules are
held together by hydrogen
bonds between hydroxyl
groups attached to carbon
atoms 3 and 6.
Figure 5.8
O
CH2OH
O
OH O
OH
CH2OH
O O
O OH
OH
OH
OH
O O
CH2OH
OH
OH
O O
CH2OH
CH2OH
O O
OH
OH
CH2OH
O O
OH
OH
 Glucose
OH
OH
O O
CH2OH
OH
Cellulose
molecules
OH
O O
CH2OH
OH
OH O
O
CH2OH
A cellulose molecule
is an unbranched 
glucose polymer.
monomer
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• Cellulose is difficult to digest
– However, it does contribute to “roughage” in the
diet  fibre
– Cows have microbes in their stomachs to facilitate
this process
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Figure 5.9
• Chitin, another important structural
polysaccharide
– Is found in the exoskeleton of arthropods
– Can be used as surgical thread
CH2OH
O OH
H
H
OH H
OH
H
H
NH
C
O
CH3
(a) The structure of the
chitin monomer.
Figure 5.10 A–C
(b) Chitin forms the exoskeleton
of arthropods. This cicada
is molting, shedding its old
exoskeleton and emerging
in adult form.
(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
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LIPIDS
Lipids
• Lipids are hydrophobic molecules
• Mostly C-H (non-polar)
• are the one class of large biological
molecules that do not consist of
polymers
• Uses: structure of cell membranes,
energy source
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Lipids
• Fats
• Phospholipids
• Steroids
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Fats
– Are constructed from two types of smaller
molecules:
• single glycerol and
• three fatty acids
Fatty Acid
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Glycerol
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ESTER
LINKAGE
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• Saturated fatty acids
– Have the maximum number of hydrogen
atoms possible
– Have no double bonds
– Are solid at room temperature (e.g. animal
fats)
Stearic acid
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(a) Saturated fat and fatty acid
Figure 5.12
• Unsaturated fatty acids
– Have one or more double bonds, causing a bend
in its structure
– Are liquids at room temperature (e.g. vegetable
fats)
Oleic acid
Figure 5.12 (b) Unsaturated fat and fatty acid
cis double bond
causes bending
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Unsaturated Fats
• Monounsaturated fats (MUFA)
– Have one double bond in their fatty
acids
•Polyunsaturated fats (PUFA)
Have more than one
double bond in their
fatty acid chains
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Phospholipids
– Have only two fatty acids
– Have a phosphate group instead of a third
fatty acid
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• Phospholipid structure
– Consists of a hydrophilic “head” and
hydrophobic “tails”
CH2
CH2
O
O
P
O–
+
N(CH3)3
Choline
Phosphate
O
CH2
CH
O
O
C
O C
CH2
Glycerol
O
Fatty acids
Hydrophilic
head
Hydrophobic
tails
Figure 5.13
(a) Structural formula
(b) Space-filling model
(c) Phospholipid
symbol
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Micelles
• When phospholipids are added to water, they
form micelles
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Phospholipid Bilayer
– Results in a phospholipid bilayer arrangement
found in cell membranes
Hydrophilic
head
WATER
Water and other
polar and ionic
materials cannot pass
through the
membrane except by
the help of proteins
in the membrane
WATER
Hydrophobic
tail
re 5.14
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Steroids
• Steroids
– Are lipids that have a carbon skeleton consisting of
four fused rings
– Contain many different functional groups
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• One steroid, cholesterol
– Is found in cell membranes
– Is a precursor for some hormones
H 3C
CH3
CH3
CH3
CH3
Figure 5.15
HO
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NUCLEIC ACIDS
Nucleic Acids
• Nucleic acids store and transmit
hereditary information
• There are two types of nucleic acids
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
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Function of DNA and RNA
• DNA
– Stores information for the synthesis of
specific proteins
– Found in the nucleus of cells
• RNA
– Reads information in DNA
– Transports information to protein building
structures within cell
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The Structure of Nucleic Acids
• Nucleic acids (also called
Polynucleotides)
5’ end
5’C
O
3’C
– Are polymers made up of
individual nucleotide
monomers
O
O
5’C
(a) Polynucleotide,
or nucleic acid
Figure 5.26
O
3’C
OH
3’ end
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• Each Nucleotide contains
– Sugar + phosphate + nitrogen base
Nucleoside
Nitrogenous
base
O

O
P
5’C
O
CH2
O
O
Phosphate
group
Figure 5.26
3’C
Pentose
sugar
(b) Nucleotide
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Nucleotide Monomers
Nitrogenous bases
Pyrimidines
NH2
(c) Nucleoside components
C
N
O
O
C
HN
CH
CH
N
C
Cytosine
C
N
CH3
C
CH
HC
C
C
N
H
CH
CH
CH
CH
H
Thymine (in DNA)
T
Uracil
(inRNA)
RNA)
Uracil (in
UU
C
N
CH
N
Pyrimidines
(single ring)
O
N
C
C
HC
N
H
Adenine
A
NH
C
N
NH2
Guanine
G
Purines
(double
ring)
Pentose sugars
5”
HOCH2
OH
O
H
H
4’
C
O
NH2
N
C
HN
N
H
O
H
C
O
H
3’
OH
2’
1’
H
H
Deoxyribose (in DNA)
Figure 5.26
5”
HOCH2
H
H
4’
H
OH
O
3’
OH
2’
1’
H
OH
Ribose
Ribose (in
(in RNA)
RNA)
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e 5.26
Nucleotide Polymers
5’ end
5’C
• nucleotides linked by
the–OH group on the
3´ carbon of one
nucleotide and the
phosphate on the 5´
carbon on the next
• Phosphodiester
bond
O
3’C
O
O
5’C
O
3’C
OH
3’ end
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Gene
• The sequence of bases along a
nucleotide polymer
– Is unique for each gene
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The DNA Double Helix
• Have two polynucleotides that
spiral around each other
• held together by hydrogen
bonds between nitrogenous
bases
– A (adenine) will always bond with T
(thymine – DNA only), or U (uracil
– RNA only)  2 hydrogen bonds
– C (cytosine) will always bond with
G (guanine)  3 hydrogen bonds
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• The DNA double helix
– Consists of two antiparallel nucleotide strands
5’ end
3’ end
Sugar-phosphate
backbone
Base pair (joined by
hydrogen bonding)
Old strands
A
3’
end
Nucleotide
about to be
added to a
new strand
5’ end
3’ end
Figure 5.27
5’ end
New
strands
3’ end
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