Reece, Taylor, Simon, and Dickey -...

© 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

© 2012 Pearson Education, Inc.

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.


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


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!!


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.


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.



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.



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.


Animation: Polymers

Figure 3.3A_s2

Short polymer Unlinkedmonomer

Dehydration reactionforms a new bond

Longer polymer

Figure 3.3B_s2

Hydrolysisbreaks a bond

CARBOHYDRATES


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.


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


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.



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.


Animation: Polysaccharides


Cellulose

– is a polymer of glucose and

– forms plant cell walls.

Chitin is

– a polysaccharide and

– used by insects and crustaceans to build anexoskeleton.


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


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.



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.



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.


Animation: Fats

Figure 3.8B

Fatty acid

Glycerol

Figure 3.8C

Fatty acids

Glycerol


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.



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.


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.


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.


PROTEINS


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)



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)



Amino acids are classified as either

– hydrophobic or

– hydrophilic.


Hydrophobic Hydrophilic

Aspartic acid (Asp)Serine (Ser)Leucine (Leu)


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.


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.



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.


NUCLEIC ACIDS


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.



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).



A nucleic acid polymer, a polynucleotide, forms

– from the nucleotide monomers,

– when the phosphate of one nucleotide bonds to thesugar of the next nucleotide


Figure 3.15B

A

T

C

G

T

Nucleotide

Sugar-phosphatebackbone


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.


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.


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.


Figure 3.12B

Groove

Figure 3.12C

Groove


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.


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



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.



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.



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.



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.


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



Beta pleatedsheet

Alpha helix

Hydrogenbond

Secondary structure

Figure 3.13A-C_s3



Beta pleatedsheet

Alpha helix

Hydrogenbond

Secondary structure

Tertiary structure Transthyretinpolypeptide

Figure 3.13A-D_s4



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.


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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