Transcript Modules03-01to03

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 3
The Molecules of Cells
Modules 3.1 – 3.3
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Spider Silk: Stronger than Steel
• Life’s diversity results from the
variety of molecules in cells
• A spider’s web-building skill
depends on its DNA molecules
• DNA also determines the structure
of silk proteins
– These make a spider web strong and
resilient
– Spider silk is an extremely strong material
and is on weight basis stronger than steel.
It has been suggested that a pencil thick
strand of silk could stop a Boeing 747 in
flight.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The capture strand contains a single coiled silk
fiber coated with a sticky fluid
The coiled fiber unwinds to capture
prey and then recoils rapidly.
The spider can easily recycle the
silk by eating it.
The web is easily destroyed by bad
weather and by catching prey.
After a day or two the adhesive
droplets of glue also lose their
adhesiveness. The old web is eaten
and a new web is constructed
again. The cutting and the
digesting of the web are done by
special digestive juices that contain
enzymes rather than by any
mechanical cutting. These juices
are also used to connect the
strands of silk together.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Coiled fiber
of silk protein
Coating of
capture strand
INTRODUCTION TO ORGANIC COMPOUNDS
AND THEIR POLYMERS
• Life’s structural and functional diversity results
from a great variety of molecules
• Over 2 million organic molecules are known.
• A relatively small number of structural patterns
underlies life’s molecular diversity
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3.1 Life’s molecular diversity is based on the
properties of carbon
• A carbon atom forms four covalent bonds
– It can join with other carbon atoms to make
straight chains, branched chains or rings
Structural
formula
Ball-and-stick
model
Space-filling
model
Methane
The 4 single bonds of carbon point to the corners of a tetrahedron.
Figure 3.1, top part
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• Carbon skeletons vary in many ways
Ethane
Propane
Carbon skeletons vary in length.
Butane
Isobutane
Skeletons may be unbranched or branched.
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
Cyclohexane
Benzene
Skeletons may be arranged in rings.
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Figure 3.1, bottom part
3.2 Functional groups help determine the
properties of organic compounds
• Functional groups are the groups of atoms that
participate in chemical reactions
– Hydroxyl groups (OH) are characteristic of alcohols. ex
ethanol
– The carboxyl group (COOH) acts as an acid. ex acetic
acid or vinegar
– The carbonyl group (C=O) . Ex. Sugars typically have a
hydroxyl and carbonyl group
– An amino group (NH2) ex. Amino acids contain both an
amino group and a carboxyl group
– A phosphate group (OPO3-2) is typically involved in
energy transfer.
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Table 3.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
3.3 Cells make a huge number of large molecules
from a small set of small molecules
• Most of the large molecules in living things are
macromolecules called polymers
– Polymers are long chains of smaller molecular
units called monomers
– A huge number of different polymers can be
made from a small number of monomers
– Linked polymers form macromolecules
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cells link monomers to form polymers by
dehydration synthesis
1
2
3
Short polymer
Unlinked monomer
Removal of
water molecule
1
2
Figure 3.3A
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3
Longer polymer
4
• Polymers are broken down to monomers by the
reverse process, hydrolysis
1
2
3
4
Addition of
water molecule
1
2
3
Coating of
capture strand
Figure 3.3B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings