© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh EditionReece, Taylor, Simon, and Dickey
Chapter 3Chapter 3 The Molecules of Cells
Figure 3.0_1
Chapter 3: Big Ideas
Introduction to OrganicCompounds Carbohydrates
Lipids Proteins
Nucleic Acids
INTRODUCTION TO ORGANICCOMPOUNDS
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3.1 Life’s molecular diversity is based on theproperties of carbon
Carbon-based molecules are called organic compounds.
By sharing electrons, carbon can– bond to four other atoms
– branch in up to four directions
– Make single, double or triple bonds
Hydrocarbons --- compounds of only carbon andhydrogen.
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A carbon skeleton is a chain of carbon atoms thatcan be
– branched or
– unbranched.
Compounds with the same formula but differentstructural arrangements are call isomers.
3.1 Life’s molecular diversity is based on theproperties of carbon
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Animation: Isomers
Animation: L-Dopa
Animation: Carbon Skeletons
Figure 3.1B
Length. Carbon skeletons vary in length.
Ethane Propane
Butane Isobutane
Branching. Skeletons may be unbranchedor branched.
Double bonds. Skeletons may have double bonds.
1-Butene 2-Butene
Cyclohexane Benzene
Rings. Skeletons may be arranged in rings.
3.2 A few chemical groups are key to thefunctioning of biological molecules
An organic compound has unique properties thatdepend upon the
– size and shape of the molecule and
– functional groups attached to it.
A functional group affects a biological molecule’sfunction in a characteristic way.
Functional groups increase hydrophilic propertiesthan hydrocarbon alone!!
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Table 3.2
3.2 A few chemical groups are key to thefunctioning of biological molecules
An example of similar compounds that differ only infunctional groups is sex hormones.
– Male and female sex hormones differ only in functionalgroups.
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Testosterone Estradiol
3.3 Cells make a huge number of large moleculesfrom a limited set of small molecules
There are four classes of molecules important toorganisms:
– carbohydrates,
– proteins,
– lipids, and
– nucleic acids.
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3.3 Cells make a huge number of large moleculesfrom a limited set of small molecules
The four classes of biological molecules containvery large molecules.
– They are often called macromolecules because of theirlarge size.
– They are also called polymers because they are madefrom identical building blocks strung together.
– The building blocks of polymers are called monomers.
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3.3 Cells make a huge number of large moleculesfrom a limited set of small molecules
Monomers are linked together to form polymersthrough dehydration reactions, which removewater.
Polymers are broken apart by hydrolysis, theaddition of water.
All biological reactions of this sort are mediated byenzymes, which speed up chemical reactions incells.
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Animation: Polymers
Figure 3.3A_s2
Short polymer Unlinkedmonomer
Dehydration reactionforms a new bond
Longer polymer
Figure 3.3B_s2
Hydrolysisbreaks a bond
CARBOHYDRATES
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3.4 Monosaccharides are the simplestcarbohydrates
Carbohydrates range from small sugar molecules to largepolysaccharides.
Sugar monomers are monosaccharides:– glucose
– Fructose
– galactose
Monosaccharides are
– the main fuels for cellular work and
– used as raw materials to manufacture other organic molecules.
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Figure 3.4B
Glucose(an aldose)
Fructose(a ketose)
Figure 3.4C
Structuralformula
Abbreviatedstructure
Simplifiedstructure
6
5
4
3 2
1
3.5 Two monosaccharides are linked to form adisaccharide
Two monosaccharides form a disaccharide bydehydration reaction.
– Sucrose = glucose + fructose
– Maltose = glucose + glucose
– Lactose = glucose + galactose
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Animation: Disaccharides
Figure 3.5_s2
Glucose Glucose
Maltose
3.7 Polysaccharides are long chains of sugar units
Polysaccharides are
– macromolecules and
– polymers composed of thousands of monosaccharides.
Polysaccharides may function as
– storage molecules or
– structural compounds.
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3.7 Polysaccharides are long chains of sugar units
Starch is
– a polysaccharide,
– composed of glucose monomers, and
– used by plants for energy storage.
Glycogen is
– a polysaccharide,
– composed of glucose monomers, and
– used by animals for energy storage.
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Animation: Polysaccharides
3.7 Polysaccharides are long chains of sugar units
Cellulose
– is a polymer of glucose and
– forms plant cell walls.
Chitin is
– a polysaccharide and
– used by insects and crustaceans to build anexoskeleton.
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Figure 3.7
Starch granulesin potato tuber cells
Glycogen granulesin muscletissue Glycogen
Glucosemonomer
Starch
Cellulose
Hydrogen bonds
Cellulosemolecules
Cellulose microfibrilsin a plant cell wall
LIPIDS
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3.8 Fats are lipids that are mostly energy-storagemolecules
Lipids
– are water insoluble (hydrophobic, or water-fearing)compounds,
– are important in long-term energy storage,
– contain twice as much energy as a polysaccharide, and
– consist mainly of carbon and hydrogen atoms linked bynonpolar covalent bonds.
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3.8 Fats are lipids that are mostly energy-storagemolecules
We will consider three types of lipids:
– Fats (triglyceride)
– phospholipids
– steroids.
A fat (triglyceride) is a large lipid made from twokinds of smaller molecules,
– 1 glycerol
– 3 fatty acids.
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3.8 Fats are lipids that are mostly energy-storagemolecules
A fatty acid can link to glycerol by a dehydrationreaction.
Fat = 1 glycerol attached to 3 fatty acids
Fats are often called triglycerides because of theirstructure.
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Animation: Fats
Figure 3.8B
Fatty acid
Glycerol
Figure 3.8C
Fatty acids
Glycerol
3.8 Fats are lipids that are mostly energy-storagemolecules
Some fatty acids contain one or more doublebonds, forming unsaturated fatty acids that
– have one fewer hydrogen atom on each carbon of thedouble bond,
– cause kinks or bends in the carbon chain, and
– prevent them from packing together tightly andsolidifying at room temperature.
Fats with the maximum number of hydrogens arecalled saturated fatty acids.
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3.8 Fats are lipids that are mostly energy-storagemolecules
Unsaturated fats include corn and olive oils.
Most animal fats are saturated fats.
Hydrogenated vegetable oils are unsaturated fatsthat have been converted to saturated fats byadding hydrogen.
This hydrogenation creates trans fats associatedwith health risks.
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3.9 Phospholipids and steroids are importantlipids with a variety of functions
Phospholipids are
– the major components of all cell membranes
Phospholipids are structurally similar to fats.
– Phospholipids contain 2 fatty acids attached to glycerol.
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Figure 3.9A-B
Water
Hydrophobic tails
Water
Hydrophilic heads
Symbol for phospholipid
Phosphategroup
Glycerol
3.9 Phospholipids and steroids are importantlipids with a variety of functions
Steroids are lipids in which the carbon skeletoncontains four fused rings.
Cholesterol is a
– common component in animal cell membranes and
– starting material for making steroids, including sexhormones.
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PROTEINS
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3.11 Proteins are made from amino acids linkedby peptide bonds
Proteins are composed of differing arrangements ofa common set of just 20 amino acid monomers.
Amino acids have
– an amino group and
– a carboxyl group (which makes it an acid).
Also bonded to the central carbon is
– a hydrogen atom and
– Side chain (R group)
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3.11 Proteins are made from amino acids linkedby peptide bonds
Amino acids have
– an amino group and
– a carboxyl group (which makes it an acid).
Also bonded to the central carbon is
– a hydrogen atom and
– Side chain (R group)
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3.11 Proteins are made from amino acids linkedby peptide bonds
Amino acids are classified as either
– hydrophobic or
– hydrophilic.
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Hydrophobic Hydrophilic
Aspartic acid (Asp)Serine (Ser)Leucine (Leu)
3.11 Proteins are made from amino acids linkedby peptide bonds
Amino acid monomers are linked together
– joining carboxyl group of one amino acid to the aminogroup of the next amino acid, and
– creating a peptide bond.
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3.12 A protein’s specific shape determines itsfunction
Probably the most important role for proteins is asenzymes, proteins that
– serve as metabolic catalysts and
– regulate the chemical reactions within cells.
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3.12 A protein’s specific shape determines itsfunction
Other proteins are also important.– Structural proteins provide associations between body parts.
– Contractile proteins are found within muscle.
– Defensive proteins include antibodies of the immune system.
– Signal proteins are best exemplified by hormones and otherchemical messengers.
– Receptor proteins transmit signals into cells.
– Transport proteins carry oxygen.
– Storage proteins serve as a source of amino acids for developingembryos.
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NUCLEIC ACIDS
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3.14 DNA and RNA are the two types of nucleicacids
Genes consist of DNA(deoxyribonucleic acid), atype of nucleic acid.
– DNA is inherited from an organism’s parents..
– DNA programs a cell’s activities by directing thesynthesis of proteins.
DNA works through an intermediary, ribonucleicacid (RNA).
– DNA is transcribed into RNA.
– RNA is translated into proteins.© 2012 Pearson Education, Inc.
Figure 3.14_s3
Gene
DNA
Transcription
RNA
ProteinTranslation
Aminoacid
Nucleic acids
3.15 Nucleic acids are polymers of nucleotides
DNA (deoxyribonucleic acid) and RNA(ribonucleic acid) are composed of monomerscalled nucleotides.
Nucleotides have three parts:
– a five-carbon sugar called ribose in RNA anddeoxyribose in DNA,
– a phosphate group, and
– a nitrogenous base.
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3.15 Nucleic acids are polymers of nucleotides
DNA nitrogenous bases are
– adenine (A),
– thymine (T),
– cytosine (C), and
– guanine (G).
RNA
– also has A, C, and G,
– but instead of T, it has uracil (U).
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3.15 Nucleic acids are polymers of nucleotides
A nucleic acid polymer, a polynucleotide, forms
– from the nucleotide monomers,
– when the phosphate of one nucleotide bonds to thesugar of the next nucleotide
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Figure 3.15B
A
T
C
G
T
Nucleotide
Sugar-phosphatebackbone
3.15 Nucleic acids are polymers of nucleotides
Two polynucleotide strands wrap around eachother to form a DNA double helix.
– The two strands are associated because particularbases always hydrogen bond to one another.
– A pairs with T, and C pairs with G, producing basepairs.
RNA is usually a single polynucleotide strand.
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Figure 3.15C
Basepair
A
C
T
GC
C G
T A
C G
A T
TA
G C
TA
TA
AT
Figure 3.UN01
Short polymer Monomer
Dehydration
HydrolysisLonger polymer
Figure 3.UN03
Carbohydrates
Monosaccharides
Lipids(don’t form polymers)
Glycerol
Components of a fat molecule
Proteins
Fatty acid
g. h.
i.
Nucleic Acids
Amino acid
o.
p.
q.Nucleotide
s.
Receive signals
DNA and RNA
Receptor protein
Heredity
Storage Egg albuminAntibodiesSignal proteins
MusclesHair, tendonsLactase
TransportCommunicationn.
l.k.j.
f.
m.
Hormones
r.
e. Phospholipids
Energy storage
Plant cell support
Starch, glycogen
Energy for cell,raw material
Functions ExamplesClasses of Moleculesand Their Components
b.
a.
c.
d.
Figure 3.UN03_1
Carbohydrates
Monosaccharides
Lipids(don’t form polymers)
Glycerol
Components of a fat molecule
Fatty acid
f.Hormones
e. Phospholipids
Plant cell support
Starch, glycogen
Energy for cell,raw material
Functions ExamplesClasses of Moleculesand Their Components
b.
a.
c.
d.Energy storage
Figure 3.UN03_2
Functions ExamplesClasses of Moleculesand Their ComponentsProteinsg. h.
i.
Nucleic Acids
Amino acid
o.
q.Nucleotide
s.
Receive signals
DNA and RNA
Receptor protein
Heredity
Storage Egg albuminAntibodiesSignal proteins
MusclesHair, tendonsLactase
TransportCommunicationn.
l.
j.
m.
r.p.
k.
3.12 A protein’s specific shape determines itsfunction
A polypeptide chain contains hundreds orthousands of amino acids linked by peptide bonds.
The amino acid sequence causes the polypeptideto assume a particular shape.
The shape of a protein determines its specificfunction.
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Figure 3.12B
Groove
Figure 3.12C
Groove
3.12 A protein’s specific shape determines itsfunction
If a protein’s shape is altered, it can no longerfunction.
In the process of denaturation, a polypeptidechain
– unravels,
– loses its shape, and
– loses its function.
Proteins can be denatured by changes in saltconcentration, pH, or by high heat.
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Figure 3.UN06
Temperature (°C)
Enzyme A Enzyme BR
ate
ofre
actio
n
0 20 60 80 10040
3.13 A protein’s shape depends on four levels ofstructure
A protein can have four levels of structure:
– primary structure
– secondary structure
– tertiary structure
– quaternary structure
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3.13 A protein’s shape depends on four levels ofstructure
The primary structure of a protein is its uniqueamino acid sequence.
– The correct amino acid sequence is determined by thecell’s genetic information.
– The slightest change in this sequence may affect theprotein’s ability to function.
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3.13 A protein’s shape depends on four levels ofstructure
Protein secondary structure results from coilingor folding of the polypeptide.
– Coiling results in a helical structure called an alphahelix.
– A certain kind of folding leads to a structure called apleated sheet, which dominates some fibrous proteinssuch as those used in spider webs.
– Coiling and folding are maintained by regularly spacedhydrogen bonds between hydrogen atoms and oxygenatoms along the backbone of the polypeptide chain.
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3.13 A protein’s shape depends on four levels ofstructure
The overall three-dimensional shape of apolypeptide is called its tertiary structure.
– Tertiary structure generally results from interactionsbetween the R groups of the various amino acids.
– Disulfide bridges may further strengthen the protein’sshape.
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3.13 A protein’s shape depends on four levels ofstructure
Two or more polypeptide chains (subunits) associateproviding quaternary structure.– Collagen is an example of a protein with quaternary
structure.– Collagen’s triple helix gives great strength to connective
tissue, bone, tendons, and ligaments.
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Animation: Secondary Protein Structure
Animation: Primary Protein Structure
Animation: Quaternary Protein Structure
Animation: Tertiary Protein Structure
Animation: Protein Structure Introduction
Figure 3.13A_s1
Primary structureAminoacids Amino acids
Four Levels of Protein Structure
Figure 3.13A-B_s2
Primary structureAminoacids Amino acids
Four Levels of Protein Structure
Beta pleatedsheet
Alpha helix
Hydrogenbond
Secondary structure
Figure 3.13A-C_s3
Primary structureAminoacids Amino acids
Four Levels of Protein Structure
Beta pleatedsheet
Alpha helix
Hydrogenbond
Secondary structure
Tertiary structure Transthyretinpolypeptide
Figure 3.13A-D_s4
Primary structureAminoacids Amino acids
Four Levels of Protein Structure
Beta pleatedsheet
Alpha helix
Hydrogenbond
Secondary structure
Tertiary structure Transthyretinpolypeptide
Quaternary structure
Transthyretin, with fouridentical polypeptides
You should now be able to
1. Describe the importance of carbon to life’smolecular diversity.
2. Describe the chemical groups that are importantto life.
3. Explain how a cell can make a variety of largemolecules from a small set of molecules.
4. Define monosaccharides, disaccharides, andpolysaccharides and explain their functions.
5. Define lipids, phospholipids, and steroids andexplain their functions.
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You should now be able to
6. Describe the chemical structure of proteins andtheir importance to cells.
7. Describe the chemical structure of nucleic acidsand how they relate to inheritance.
8. Explain how lactose tolerance has evolved inhumans.
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