Download Chapter 5

Overview: The Molecules of Life
Chapter 5-1 & 5-2
The Structure and Function of
Large Biological Molecules
• All living things are made up of four classes of
large biological molecules:
– Carbohydrates
– Lipids
– Proteins
PowerPoint®
Lecture Presentations for
Biology
Polymerization
– nucleic acids
Carbohydrates
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Question:
Overview: The Molecules of Life
• How do cells synthesize and break
down macromolecules?
• Within cells, small organic molecules are joined
together to form larger molecules
• Macromolecules are large molecules
composed of thousands of covalently
connected atoms
• Molecular structure and function are
inseparable
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-1—studying the structure of macromolecules
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
1
The Synthesis and Breakdown of Polymers
Fig. 5-2
HO
–
1
2
3
HO
H
H
Unlinked monomer
Short polymer
• Dehydration synthesis (also called dehydration
polymerization or a condensation reaction) occurs when two
monomers bond together through the loss of a water molecule
Dehydration removes a water
molecule, forming a new bond
The hydroxyl group of one monomer and a hydrogen atom from
the other monomer are removed
HO
2
1
H2O
H
4
3
Longer polymer
–
A covalent bond forms between the two monomers
–
The hydroxyl group and the hydrogen atom bond to produce a
water molecule (dehydration)
Dehydration reaction in the synthesis of a polymer
Condensation Polymerization
Loss of water, formation of larger
molecules
Loss of water/ formation of larger molecules
A-OH + H-B
A-B + H2O
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Synthesis and Breakdown of Polymers
Fig. 5-2
HO
• Enzymes are macromolecules that speed up the
dehydration process
• Polymers are broken down into monomers by
hydrolysis, a reaction that is essentially the reverse
of the dehydration reaction
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
1
2
3
H
H
H2O
HO
H
Hydrolysis of a polymer
– Water is split (hydro = water/ lysis = to split) by
enzymes
Hydrolysis
– The covalent bond between the monomers is broken
– A hydroxyl group from water is added to one monomer
and a hydrogen atom is added to the other
Gain of water, breakdown of molecules
into smaller units
A-B + H2O
– Occurs during digestion
A-OH + H-B
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The name of the bond formed varies depending on
which atoms wind up bonded together
MONOMERS
POLYMERS
BOND
Monosaccharides
Polysaccharides
Glycosidic linkage
(carbohydrates)
Glycerol, fatty acids
Triglycerides
Ester bonds
(a type of lipid)
Amino acids
Peptide chains
Peptide bond
(proteins)
Nucleotides
Nucleic acids
Phosphodiester linkage
• Ester bonds—join fatty acids to glycerol
– The bonding of a hydroxyl group to a carbon with a
carbonyl
• Glycosidic linkage—bonds two sugar monomers
together
• Peptide bond—the nitrogen of one amino acid is
bonded to the carbon of the next amino acid to form
polypeptides
(DNA & RNA)
Animation: Polymers
• Sugar-phosphate bond—the sugar of one nucleotide
is bonded to the phosphate of another nucleotide to
form nucleic acids
2
The Diversity of Polymers
Concept check
• Each cell has thousands of different kinds of
macromolecules 2 3
H
HO
• Macromolecules vary among cells of an
organism, vary more within a species, and vary
even more between species
• An immense variety of polymers can be built
from a small set of monomers
1. What are the four main classes of large
biological molecules?
2. How many molecules of water are needed to
completely hydrolyze a polymer that is ten
monomers long?
3. Suppose you eat a serving of green beans.
What reactions must occur for the amino acid
monomers in the protein of the beans to be
converted to proteins in your body?
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
4. What is the formula for a monosaccharide
that has three carbons? C H O
3
6
3
5. A dehydration reaction joins two glucose
molecules to form maltose. The formula for
glucose is C6H12O6. What is the formula for
maltose?
C12H22O11
6. The molecular formula for glucose is C6H12O6.
What would be the molecular formula for a
polymer made by linking ten glucose
molecules together by dehydration reactions?
C60H102O51
Essential Question
7. Enzymes that break down DNA catalyze the
hydrolysis of the covalent bonds that join nucleotides
together. What would happen to DNA molecules
treated with these enzymes?
• How do structures of biologically important
molecules (carbohydrates, lipids, proteins,
nucleic acids) account for their function?
a) The two strands of the double helix would separate.
b) The phosphodiester linkages between deoxyribose
sugars would be broken.
c) The purines would be separated from the deoxyribose
sugars.
d) The pyrimidines would be separated from the
deoxyribose sugars.
e) All bases would be separated from the deoxyribose
sugars.
3
Concept 5.2: Carbohydrates serve as fuel and
building material
• Carbohydrates include sugars and the
polymers of sugars
Sugars— soluble in water because of hydroxyl group
• Monosaccharides (simple sugars)
– Glucose (C6H12O6) is the most common
monosaccharide
– The simplest carbohydrates are
monosaccharides, or single sugars
– have molecular formulas that are usually
multiples of CH2O
– classified by
• The location of the carbonyl group (as
aldose or ketose)
• Carbohydrate macromolecules are
polysaccharides, polymers composed of many
sugar building blocks
• The number of carbons in the carbon
skeleton
– Have 3-7 carbons
– Include cellulose, chitin, and glycoproteins
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-3
Fig. 5-3a
Trioses (C3H6O3)
Pentoses (C5H10O5)
Hexoses (C6H12O6)
Aldoses
Trioses (C3H6O3)
Pentoses (C5H10O5)
Hexoses (C6H12O6)
Glyceraldehyde
Ketoses
Glucose
Galactose
Aldoses
Ribose
Glyceraldehyde
Ribose
Glucose
Galactose
Dihydroxyacetone
Ribulose
Fructose
Fig. 5-3b
Ketoses
Trioses (C3H6O3)
Pentoses (C5H10O5)
Hexoses (C6H12O6)
• Though often drawn as linear skeletons, in
aqueous solutions many sugars form rings
• Monosaccharides serve as a major fuel for
cells and as raw material for building
molecules
Dihydroxyacetone
Ribulose
Fructose
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4
Fig. 5-4
Fig. 5-4a
In aqueous solutions, the most common form
for sugars is the ring
(a) Linear and ring forms
(b) Abbreviated ring structure
36% of glucose is in
the Alpha form in
solution—the -OH on
carbon 1 is down
(a) Linear and ring forms
In Beta glucose, the –OH on carbon 1 is up/ 64% of
glucose molecules in solution are Beta glucose
Fig. 5-5
1–4
glycosidic
linkage
• A disaccharide is formed when a dehydration
reaction joins two monosaccharides
• This covalent bond between two
monosaccharides is called a glycosidic
linkage
alpha
Glucose
alpha
Glucose
(a) Dehydration reaction in the synthesis of maltose
Maltose Plant
sugar
1–2
glycosidic
linkage
alpha
Glucose
beta
Fructose
(b) Dehydration reaction in the synthesis of sucrose
Sucrose Table
sugar
Animation: Disaccharides
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Polysaccharides
• Polysaccharides, the polymers of sugars,
have storage and structural roles
Storage Polysaccharides
• Starch
– consists of long chains of glucose
monomers that are digestible
– Formed from 3 or more monosaccharides
–
bonding produces helical molecules
– Starch, glycogen, cellulose, chitin
• Amylose—unbranched chains
• The structure and function of a polysaccharide
are determined by its sugar monomers and the
positions of glycosidic linkages
• Amylopectin—branched chains
– a storage polysaccharide of plants
• Surplus starch is stored as granules within
chloroplasts and other plastids
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5
Fig. 5-6
Storage Polysaccharides
Chloroplast
Starch
• Glycogen
– Long chains of glucose molecules that are
extensively branched
– a storage polysaccharide in animals
1 µm
Note the helical
structure of amylose
and amylopectin
molecules
Amylose
• Humans and other vertebrates store
glycogen mainly in liver (1 day’s worth) and
muscle cells
Amylopectin
Starch: a plant polysaccharide
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Mitochondria Glycogen granules
Structural Polysaccharides
• cellulose
– The most abundant organic molecule
• a major component of the tough wall of plant cells
• Digested only by some bacteria and fungi (NOT by
animals)
0.5 µm
Note the extensive
branching of the long
chains
– Made entirely of β glucose monomers
• Forms straight parallel strands (microfibrils) that are
linked by hydrogen bonds between hydroxyl groups
and hydrogen atoms. The microfibrils then
intertwine to form cellulose fibrils which are strong
building materials for plants.
Glycogen
Glycogen: an animal polysaccharide
Animation: Polysaccharides
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-7
Fig. 5-8
Cell walls
The difference in starches and cellulose is the type of
glycosidic linkages
α
and β glucose
ring structures
Cellulose
microfibrils
in a plant
cell wall
Microfibril
10 µm
0.5 µm
Glucose
β Glucose
Cellulose
molecules
Starch: 1–4 linkage of α glucose monomers
Cellulose: 1–4 linkage of β glucose monomers
β Glucose
monomer
6
Cellulose-digesting
Prokaryotes are found in
the rumen of this cow
Digestion
• The structure of these molecules affects animals’
ability to digest them
– Enzymes that digest starch by hydrolyzing α linkages
can’t hydrolyze β linkages in cellulose
Structural Polysaccharides
• Chitin
– found in the exoskeleton of arthropods, in
some sponges, & in the cell walls of many
fungi
– Cellulose in human food passes through the digestive
tract as insoluble fiber and functions to stimulate the
production of mucus, which aids in elimination of
wastes from the digestive tract.
• Some microbes use enzymes to digest cellulose
– Many herbivores, from cows to termites, have
symbiotic relationships with these microbes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Amino sugar
Chitin forms the
exoskeleton of
arthropods.
Chitin is used to make
a strong and flexible
surgical thread.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Quick Quiz
Quick quiz
1. What is the formula for a monosaccharide
that has three carbons?
2. Which term includes all others in the list?
C3H6O3
a) Monosaccharide
b) Disaccharide
c) Starch
d) Carbohydrate
e) Polysaccharide
Quick Quiz
Quick quiz
3. What would happen if a cow were given
antibiotics that killed all of the prokaryotes in
its stomach?
4. The enzyme amylase can break glycosidic
linkages between glucose monomers only if
the monomers are the α form. Which of the
following could amylase break down?
It would starve
a) Glycogen, starch, and amylopectin
b) Glycogen and cellulose
c) Cellulose and chitin
d) Starch and chitin
e) Starch, amylopectin, and cellulose
7
Quick Quiz
5. Which types of organisms use chitin as a
structural molecule?
Arthropods (in their exoskeleton)
Some sponges (in their skeletons)
Some fungi (in their cell walls)
8