Chapter 3Chapter 3The Molecules of CellsThe Molecules of Cells

Organic Chemistry: Carbon Based CompoundsOrganic Chemistry: Carbon Based Compounds

A. A. Inorganic CompoundsInorganic Compounds: : Compounds without Compounds without carbon.carbon.

B. B. Organic CompoundsOrganic Compounds: : Compounds synthesized Compounds synthesized by cells and containing carbon (except for CO by cells and containing carbon (except for CO and COand CO22).). Diverse groupDiverse group:: Several million Several million organicorganic compounds compounds

are known and more are identified every day.are known and more are identified every day.

Common:Common: After water, After water, organicorganic compounds are the compounds are the most common substances in cells. most common substances in cells. Over 98% of the Over 98% of the dry weightdry weight of living cells is made up of of living cells is made up of

organicorganic compounds. compounds. Less than 2% of the Less than 2% of the dry weightdry weight of living cells is made up of of living cells is made up of

inorganicinorganic compounds. compounds.

CarbonCarbon: unique element for basic building block of : unique element for basic building block of molecules of lifemolecules of life

Carbon has 4 valence electrons: Carbon has 4 valence electrons: Can form four Can form four covalent bondscovalent bonds Can form single , double, triple bonds.Can form single , double, triple bonds. Can form large, complex, branching molecules and Can form large, complex, branching molecules and

rings.rings. Carbon atoms easily bond toCarbon atoms easily bond to C, N, O, H, P, S.C, N, O, H, P, S.

Huge varietyHuge variety of molecules can be formed based of molecules can be formed based on simple bonding rules of basic chemistryon simple bonding rules of basic chemistry

Organic Compounds are Carbon Based

Carbon Can Form 4 Covalent Bonds

Different Carbon Skeletons of Organic CompoundsDifferent Carbon Skeletons of Organic Compounds

Diversity of Organic CompoundsDiversity of Organic Compounds

Hydrocarbons:Hydrocarbons: Organic molecules thatOrganic molecules that contain C and H onlycontain C and H only. . Good fuels, but not biologically important.Good fuels, but not biologically important. Undergo combustion (burn in presence of oxygen).Undergo combustion (burn in presence of oxygen). In general they are chemically stable.In general they are chemically stable. NonpolarNonpolar: Do not dissolve in water (: Do not dissolve in water (HydrophobicHydrophobic).).

Examples:Examples: (1C)(1C) MethMethane: ane: CHCH4 4 (Natural gas).(Natural gas). (2C)(2C) EthEthane: ane: CHCH33CHCH33 (3C)(3C) PropPropane: ane: CHCH33CHCH22CHCH33 (Gas grills). (Gas grills). (4C)(4C) ButButane: ane: CHCH33CHCH22CHCH22CHCH3 3 (Lighters).(Lighters). (5C)(5C) PentPentane: ane: CHCH33CHCH22CHCH22CHCH22CHCH33 (6C)(6C) HexHexane: ane: CHCH33CHCH22CHCH22CHCH22CHCH22CHCH33 (7C)(7C) HeptHeptane: ane: CHCH33CHCH22CHCH22CHCH22CHCH22CHCH22CHCH33 (8C)(8C) OctOctane: ane:

CHCH33CHCH22CHCH22CHCH22CHCH22CHCH22CHCH22CHCH33

Hydrocarbons have C and H only

IsomersIsomers: Compounds with same chemical formula : Compounds with same chemical formula but but different structure different structure (arrangement(arrangement of atoms) of atoms)

IsomersIsomers have different physical and chemical have different physical and chemical properties properties

Structural IsomersStructural Isomers:: Differ in Differ in bonding arrangementsbonding arrangements

ButaneButane (C (C44HH1010)) IsobutaneIsobutane (C (C44HH1010))

CHCH33

||CHCH33--CH--CH22--CH--CH22--CH--CH33 CH CH33---CH---CH---CH---CH33

Number of possible isomers increases with increasing Number of possible isomers increases with increasing number of carbon atoms.number of carbon atoms.

Functional groupsFunctional groups play pivotal role in chemical & play pivotal role in chemical & physical properties of organic moleculesphysical properties of organic molecules

Compounds that are made up solely of carbon Compounds that are made up solely of carbon and hydrogen are not very reactive. and hydrogen are not very reactive. Functional groupsFunctional groups:: One or more H atoms of the carbon skeleton may be One or more H atoms of the carbon skeleton may be

replaced byreplaced by a a functionalfunctional group.group. Groups of atoms that have unique chemical and Groups of atoms that have unique chemical and

physical properties.physical properties.

Usually a part of molecule that is Usually a part of molecule that is chemically activechemically active.. Similar activity from one molecule to another.Similar activity from one molecule to another.

Together with size and shape, determine unique bonding and Together with size and shape, determine unique bonding and

chemical activity of organic molecules.chemical activity of organic molecules.

Functional GroupsFunctional Groups Determine Chemical & Determine Chemical & Physical Properties of Organic MoleculesPhysical Properties of Organic Molecules

Four Important Functional GroupsFour Important Functional Groups:: Hydroxyl (-OH) Hydroxyl (-OH) Carbonyl (=C=O)Carbonyl (=C=O) Carboxyl (-COOH)Carboxyl (-COOH)

Amino (-NHAmino (-NH22))

Notice that all four functional groups are Notice that all four functional groups are

polar. polar.

A. A. Hydroxyl GroupHydroxyl Group (-OH) (-OH) Is a Is a polar grouppolar group: Polar covalent bond between O and H.: Polar covalent bond between O and H.

Can form hydrogen bonds with other polar groups.Can form hydrogen bonds with other polar groups.

Generally makes molecule Generally makes molecule water soluble.water soluble.

Example:Example:

Alcohols:Alcohols: Organic molecules with a simple hydroxyl Organic molecules with a simple hydroxyl

group: group:

Methanol (wood alcohol, toxic)Methanol (wood alcohol, toxic)

Ethanol (drinking alcohol)Ethanol (drinking alcohol)

Propanol (rubbing alcohol)Propanol (rubbing alcohol)

B. B. Carbonyl GroupCarbonyl Group (=CO) (=CO)

Is a Is a polar grouppolar group: O can be involved in H-bonding.: O can be involved in H-bonding. Generally makes molecule Generally makes molecule water soluble.water soluble.

Examples:Examples: Aldehydes:Aldehydes: Carbonyl is located at Carbonyl is located at endend of molecule of molecule KetoneKetone: : Carbonyl is located Carbonyl is located in in middlemiddle of molecule of molecule

Examples:Examples: Sugars (Aldehydes or ketones)Sugars (Aldehydes or ketones) Formaldehyde (Aldehyde)Formaldehyde (Aldehyde) Acetone (Ketone)Acetone (Ketone)

Sugars Have Both -OH and =CO Functional Groups

C. C. Carboxyl GroupCarboxyl Group (-COOH) (-COOH) Is a Is a polar grouppolar group

Generally makes molecule Generally makes molecule water solublewater soluble

AcidicAcidic because it can because it can donate Hdonate H++ in solution in solution

Example:Example:

Carboxylic acidsCarboxylic acids: : Organic acids,Organic acids, can increase acidity can increase acidity

of a solution: of a solution: Acetic acid: Sour taste of vinegar.Acetic acid: Sour taste of vinegar.

Ascorbic acid (Vitamin C): Found in fruits and vegetables.Ascorbic acid (Vitamin C): Found in fruits and vegetables.

Amino acids: Building blocks of proteins. Amino acids: Building blocks of proteins.

D. D. Amino GroupAmino Group (-NH(-NH22))

Is a Is a polar grouppolar group

Generally makes molecule Generally makes molecule water solublewater soluble

Weak baseWeak base because N can accept a H because N can accept a H++

AmineAmine - -general term given to compound with (-NHgeneral term given to compound with (-NH22))

Example:Example:

Amino acidsAmino acids: Building blocks of proteins.: Building blocks of proteins.

Amino acid Structure:Amino acid Structure:

Central carbon with:Central carbon with: H atomH atom Carboxyl groupCarboxyl group Amino groupAmino group Variable R-groupVariable R-group

Amino Acid Structure:Amino Acid Structure:

HH

||

(Amino Group)(Amino Group) NHNH22---C------C---COOH (Carboxyl group)COOH (Carboxyl group) ||

RR

(Varies for each amino acid)(Varies for each amino acid)

Amino Acids Have Both -NHAmino Acids Have Both -NH22 and -COOH Groups and -COOH Groups

The Macromolecules of Life:The Macromolecules of Life:Carbohydrates, Proteins, Lipids, and Nucleic AcidsCarbohydrates, Proteins, Lipids, and Nucleic Acids

I. Most Biological Macromolecules are I. Most Biological Macromolecules are PolymersPolymers

PolymerPolymer: : Large molecule consisting of many Large molecule consisting of many identical or similar “subunits” linked through identical or similar “subunits” linked through covalent bonds.covalent bonds.

MonomerMonomer: : “Subunit” or building block of a “Subunit” or building block of a polymer.polymer.

MacromoleculeMacromolecule: : Large organic polymer. Most Large organic polymer. Most macromolecules are constructed from about 70 macromolecules are constructed from about 70 simple monomers.simple monomers.

Only about 70 monomersOnly about 70 monomers are used by are used by all living things all living things on earthon earth to construct a huge variety of molecules to construct a huge variety of molecules

Structural variation of macromoleculesStructural variation of macromolecules is the basis for is the basis for the enormous diversity of life on earth.the enormous diversity of life on earth.

Relatively few monomersRelatively few monomers are used by cells to are used by cells to

make a huge variety of macromoleculesmake a huge variety of macromolecules

MacromoleculeMacromolecule Monomers or Monomers or SubunitsSubunits

1. Carbohydrates1. Carbohydrates 20-3020-30 monosaccharides monosaccharidesor simple sugarsor simple sugars

2. Proteins2. Proteins 20 20 amino acids amino acids

3. Nucleic acids (DNA/RNA)3. Nucleic acids (DNA/RNA) 4 4 nucleotides nucleotides

(A,G,C,T/(A,G,C,T/UU))

4. Lipids (fats and oils)4. Lipids (fats and oils) ~ ~ 20 20 different fatty different fatty acidsacids

and glycerol.and glycerol.

Making and Breaking PolymersMaking and Breaking Polymers There are two main chemical mechanisms in There are two main chemical mechanisms in

the production and break down of the production and break down of macromolecules.macromolecules. Condensation or Dehydration SynthesisCondensation or Dehydration Synthesis HydrolysisHydrolysis

In the cell these mechanisms are regulated by In the cell these mechanisms are regulated by enzymes.enzymes.

Making PolymersMaking PolymersA. A. Condensation or Dehydration Synthesis reactions:Condensation or Dehydration Synthesis reactions: Synthetic process in which a monomer is Synthetic process in which a monomer is covalentlycovalently

linked to another monomer. linked to another monomer. The equivalent of a The equivalent of a waterwater molecule is molecule is removed.removed.

General Reaction:General Reaction:X - X - OHOH + + HHO - Y --------> X - O - Y + HO - Y --------> X - O - Y + H22OO

Monomer 1 Monomer 2 Dimer WaterMonomer 1 Monomer 2 Dimer Water(Unlinked) (or Polymer) (Unlinked) (or Polymer) ( (or Polymer)or Polymer)

Anabolic ReactionsAnabolic Reactions: Used by cells to make large : Used by cells to make large molecules from smaller ones.molecules from smaller ones.

Require energy (endergonic)Require energy (endergonic) Require catalysis byRequire catalysis by enzymes enzymes

Condensation Synthesis: Monomers are Linked and Water is Removed

Breaking PolymersBreaking PolymersB. B. Hydrolysis ReactionsHydrolysis Reactions: : “Break with water”.“Break with water”. Degradation of polymers into component monomers.Degradation of polymers into component monomers. Involves breaking covalent bonds between subunits.Involves breaking covalent bonds between subunits. Covalent bonds are broken by adding water.Covalent bonds are broken by adding water.

General Reaction:General Reaction: X - O - Y + HX - O - Y + H22O ----------> X - O ----------> X - OH OH + + HHO - YO - Y

PolymerPolymer WaterWater Monomer 1 Monomer 2Monomer 1 Monomer 2 (or Dimer)(or Dimer)

Catabolic ReactionsCatabolic Reactions: Used by cells to break large : Used by cells to break large molecules into smaller ones.molecules into smaller ones.

Release energy (exergonic)Release energy (exergonic) Reactions Reactions catalyzed by enzymes catalyzed by enzymes

Hydrolysis: Polymers are Broken Down as Water is Added

Hydrolysis

Making and Breaking PolymersMaking and Breaking Polymers

Examples:Examples:

Dehydration Synthesis (Condensation):Dehydration Synthesis (Condensation):

EnzymeEnzymeGlucose + Fructose ---------> SucroseGlucose + Fructose ---------> Sucrose + + H H22OO (Monomer) (Monomer)(Monomer) (Monomer) (Dimer)(Dimer) WaterWater

Hydrolysis:Hydrolysis:

EnzymeEnzymeSucroseSucrose + + H H22OO ---------> ---------> Glucose + FructoseGlucose + Fructose(Dimer)(Dimer) WaterWater (Monomer) (Monomer)(Monomer) (Monomer)

Synthesis and Hydrolysis of Sucrose

III. III. Carbohydrates:Carbohydrates: Molecules that store energy Molecules that store energy and are used as building materialsand are used as building materials

General Formula: General Formula: (CH(CH22O)nO)n

Simple sugars and their polymers.Simple sugars and their polymers. Diverse group includes sugars, starches, cellulose.Diverse group includes sugars, starches, cellulose. Biological FunctionsBiological Functions::

• Fuels, energy storage Fuels, energy storage

• Structural component (cell walls)Structural component (cell walls)

• DNA/RNA componentDNA/RNA component Three types of carbohydrates:Three types of carbohydrates:

A. A. MonosaccharidesMonosaccharidesB. B. Disaccharides Disaccharides C. C. PolysaccharidesPolysaccharides

A. A. MonosaccharidesMonosaccharides: : “Mono”“Mono” single & single & “sacchar”“sacchar” sugar sugar

Preferred source of chemical energy for cells (Preferred source of chemical energy for cells (glucoseglucose)) Can be synthesized by plants from light, HCan be synthesized by plants from light, H22O and COO and CO2.2.

Store energy in chemical bonds.Store energy in chemical bonds. Carbon skeletons used to synthesize other molecules.Carbon skeletons used to synthesize other molecules.

CharacteristicsCharacteristics::1. M1. May have 3-8 carbons. -OH on each carbon; one with C=0ay have 3-8 carbons. -OH on each carbon; one with C=0

2. Names end in 2. Names end in -ose-ose. Based on number of carbons:. Based on number of carbons: 5 carbon sugar: 5 carbon sugar: pentosepentose 6 carbon sugar: 6 carbon sugar: hexose.hexose.

3. Can exist in 3. Can exist in linearlinear or or ringring forms forms

4. 4. Isomers:Isomers: Many molecules with the same molecular Many molecules with the same molecular formula, but different atomic arrangement.formula, but different atomic arrangement. ExampleExample: Glucose and fructose are both C: Glucose and fructose are both C66HH1212OO66..

Fructose is sweeter than glucose.Fructose is sweeter than glucose.

Monosaccharides Can Have 3 to 8 Carbons

Linear and Ring Forms of Glucose

B. B. DisaccharidesDisaccharides: : “Di”“Di” double & double & “sacchar”“sacchar” sugar sugar

Covalent bond formed by condensation reaction Covalent bond formed by condensation reaction between 2 monosaccharides.between 2 monosaccharides.

ExamplesExamples::

1. 1. MaltoseMaltose: Glucose + Glucose. : Glucose + Glucose.

• Energy storage in seeds. Energy storage in seeds.

• Used to make beer.Used to make beer.

2. 2. LactoseLactose: Glucose + Galactose. : Glucose + Galactose.

• Found in milk.Found in milk.

• Lactose intoleranceLactose intolerance is common among adults. is common among adults.• May cause gas, cramping, bloating, diarrhea, etc.May cause gas, cramping, bloating, diarrhea, etc.

3. 3. SucroseSucrose: Glucose + Fructose. : Glucose + Fructose.

• Most common disaccharide (table sugar). Most common disaccharide (table sugar).

• Found in plant sap.Found in plant sap.

Maltose and Sucrose are Disaccharides

C. C. PolysaccharidesPolysaccharides: : “Poly”“Poly” many (8 to 1000) many (8 to 1000)

FunctionsFunctions: Storage of chemical energy and structure.: Storage of chemical energy and structure.

Storage polysaccharidesStorage polysaccharides: : Cells can store simple sugars Cells can store simple sugars in polysacharides and hydrolyze them when needed.in polysacharides and hydrolyze them when needed.

1. 1. StarchStarch: Glucose polymer (Helical): Glucose polymer (Helical)

Form of glucose storage in Form of glucose storage in plantsplants (amylose) (amylose) Stored in plant cell organelles called Stored in plant cell organelles called plastidsplastids

2. 2. GlycogenGlycogen: Glucose polymer (Branched): Glucose polymer (Branched)

Form of glucose storage in Form of glucose storage in animalsanimals ( (muscle and liver muscle and liver

cells)cells)

Three Different Polysaccharides of Glucose

Structural PolysaccharidesStructural Polysaccharides: : Used as structural Used as structural components of cells and tissues.components of cells and tissues.

1. 1. CelluloseCellulose: Glucose polymer.: Glucose polymer.

The major component of plant cell walls.The major component of plant cell walls. CANNOTCANNOT be digested by animal enzymes. be digested by animal enzymes. Only microbes have enzymes to hydrolyze.Only microbes have enzymes to hydrolyze.

2. 2. ChitinChitin: Polymer of an amino sugar (with NH: Polymer of an amino sugar (with NH22 group) group)

Forms exoskeleton of arthropods (insects)Forms exoskeleton of arthropods (insects) Found in cell walls of some fungiFound in cell walls of some fungi

Cellulose: Polysaccharide Found in Plant and Algae Cell Walls

ProteinsProteins: Large three-dimensional : Large three-dimensional macromolecules responsible for most cellular macromolecules responsible for most cellular functionsfunctions

Polypeptide chainsPolypeptide chains: : Polymers of amino acids linked Polymers of amino acids linked by by peptide bondspeptide bonds in a SPECIFIC linear sequence in a SPECIFIC linear sequence

ProteinProtein: : Macromolecule composed of Macromolecule composed of one or more one or more polypeptide chains folded into SPECIFIC 3-D polypeptide chains folded into SPECIFIC 3-D conformationsconformations

Proteins have important and varied functions:Proteins have important and varied functions:

1.1. EnzymesEnzymes: : Catalysis of cellular reactionsCatalysis of cellular reactions

2. 2. Structural ProteinsStructural Proteins: : Maintain cell shapeMaintain cell shape

3. 3. TransportTransport: : Transport in cells/bodies (e.g. hemoglobin). Transport in cells/bodies (e.g. hemoglobin).

Channels and carriers across cell membrane.Channels and carriers across cell membrane.

4. 4. CommunicationCommunication: : Chemical messengers, hormones, and Chemical messengers, hormones, and

receptors.receptors.

5. 5. DefensiveDefensive: : Antibodies and other molecules that bind to Antibodies and other molecules that bind to

foreign molecules and help destroy them.foreign molecules and help destroy them.

6. 6. ContractileContractile: Muscular movement.: Muscular movement.

7. 7. StorageStorage: Store amino acids for later use (e.g. egg white).: Store amino acids for later use (e.g. egg white).

Protein functionProtein function is dependent upon its 3-D shape. is dependent upon its 3-D shape.

PolypeptidePolypeptide: Polymer of amino acids connected in : Polymer of amino acids connected in a specific sequencea specific sequence

A. A. Amino acidAmino acid: : The monomer of polypeptidesThe monomer of polypeptides

Central carbonCentral carbon

• H atomH atom

• Carboxyl group Carboxyl group

• Amino groupAmino group

• Variable R-groupVariable R-group

Protein Protein FunctionFunction is dependent upon Protein is dependent upon Protein Structure Structure (Conformation) (Conformation)

CONFORMATIONCONFORMATION: : The 3-D shape of a protein is The 3-D shape of a protein is determined by its determined by its amino acid sequence.amino acid sequence.

Four Levels of Protein StructureFour Levels of Protein Structure

1. 1. Primary structurePrimary structure: : Linear amino acid Linear amino acid sequence, sequence, determined by determined by gene for that protein.gene for that protein.

2. 2. Secondary structureSecondary structure: : Regular coiling/folding Regular coiling/folding of polypeptide.of polypeptide. Alpha helix or beta sheet. Alpha helix or beta sheet. Caused by H-bonds between amino acids.Caused by H-bonds between amino acids.

Primary Structure of Protein: Amino Acid Sequence is Determined by Gene

Secondary Structure of Protein: Regular Folding Patterns (Alpha Helix or Pleated Sheet)

3. 3. Tertiary structureTertiary structure: : Overall 3-D shape of a polypeptide Overall 3-D shape of a polypeptide

chain.chain.

4. 4. Quaternary structureQuaternary structure: : Only in proteins with 2 or more Only in proteins with 2 or more polypeptides. Overall 3-D shape of all chains.polypeptides. Overall 3-D shape of all chains. Example: Hemoglobin (2 alpha and 2 beta polypeptides)Example: Hemoglobin (2 alpha and 2 beta polypeptides)

Tertiary Structure: Overall 3-D Shape of Protein

Tertiary Structure of Lysozyme

Quaternary Structure: Overall 3-D Shape of Protein with 2 or More Subunits

What determines a protein’s shape?What determines a protein’s shape?

A. A. Primary structurePrimary structure: : Exact location of each amino Exact location of each amino

acid along the chain determines the protein’s acid along the chain determines the protein’s

folding pattern.folding pattern.

ExampleExample: : Sickle Cell Hemoglobin proteinSickle Cell Hemoglobin protein Mutation changes amino acid #6 on the alpha chain.Mutation changes amino acid #6 on the alpha chain.

Defective hemoglobin causes red blood cells to assume Defective hemoglobin causes red blood cells to assume

sickle shape, which damages tissue and capillaries.sickle shape, which damages tissue and capillaries.

Sickle cell anemia gene is carried in 10% of African Sickle cell anemia gene is carried in 10% of African

Americans.Americans.

B. B. Chemical & Physical Environment:Chemical & Physical Environment:

Presence of other compounds, pH, Presence of other compounds, pH,

temperature, salts.temperature, salts.

Denaturation:Denaturation: Process which alters native Process which alters native

conformation and therefore biological conformation and therefore biological

activity of a protein. Several factors can activity of a protein. Several factors can

denature proteins:denature proteins: pH and saltspH and salts:: Disrupt hydrogen, ionic bonds.Disrupt hydrogen, ionic bonds.

TemperatureTemperature:: Can disrupt weak interactions.Can disrupt weak interactions.

• Example:Example: Function of an enzyme depends Function of an enzyme depends

on pH, temperature, and salt concentrationon pH, temperature, and salt concentration..

Nucleic acidsNucleic acids store and transmit hereditary store and transmit hereditary information for all living thingsinformation for all living things

There are two types of nucleic acids in living things:There are two types of nucleic acids in living things:

A. A. Deoxyribonucleic Acid Deoxyribonucleic Acid (DNA)(DNA) Contains genetic information of all living organisms.Contains genetic information of all living organisms. Has segments called Has segments called genesgenes which provide information to which provide information to

make each and every protein in a cellmake each and every protein in a cell Double-stranded molecule whichDouble-stranded molecule which replicates replicates each time a each time a

cell divides.cell divides.

B. B. Ribonucleic Acid Ribonucleic Acid (RNA)(RNA)

Three main types called Three main types called mRNA, tRNA, rRNAmRNA, tRNA, rRNA RNA molecules are RNA molecules are copiedcopied from DNA and used to make from DNA and used to make

gene products (proteins).gene products (proteins). Usually exists in single-stranded form.Usually exists in single-stranded form.

DNA and RNADNA and RNA are polymers of are polymers of nucleotidesnucleotides that that determine the primary structure of proteinsdetermine the primary structure of proteins

NucleotideNucleotide:: Subunits of DNA or RNA. Subunits of DNA or RNA.

Nucleotides have three components: Nucleotides have three components:

1. Pentose sugar1. Pentose sugar ( (riboseribose or or deoxydeoxyriboseribose))

2. Phosphate group to link nucleotides (-PO2. Phosphate group to link nucleotides (-PO44))

3. Nitrogenous base3. Nitrogenous base (A,G,C,T or (A,G,C,T or UU)) Purines:Purines: Have 2 rings. Have 2 rings.

Adenine (A) and guanine (G)Adenine (A) and guanine (G)

PyrimidinesPyrimidines: Have one ring. : Have one ring.

Cytosine (C), thymine (T) in DNA or Cytosine (C), thymine (T) in DNA or uracil (U) in RNA.uracil (U) in RNA.

James Watson and Francis Crick Determined the 3-James Watson and Francis Crick Determined the 3-D Shape of DNA in 1953D Shape of DNA in 1953

Double helixDouble helix:: The DNA molecule is a double helix.The DNA molecule is a double helix. AntiparallelAntiparallel: The two DNA strands run in opposite : The two DNA strands run in opposite

directions.directions. Strand 1: 5’ to 3’ direction (------------>)Strand 1: 5’ to 3’ direction (------------>) Strand 2: 3’ to 5’ direction (<------------)Strand 2: 3’ to 5’ direction (<------------)

Complementary Base Pairing:Complementary Base Pairing: A & T (U) and G & C. A & T (U) and G & C. A on one strand hydrogen bonds to T (or U in RNA). A on one strand hydrogen bonds to T (or U in RNA). G on one strand hydrogen bonds to C.G on one strand hydrogen bonds to C.

ReplicationReplication: : The double-stranded DNA molecule can The double-stranded DNA molecule can easily replicate based on easily replicate based on A=T and G=C pairing.A=T and G=C pairing.

------

SEQUENCE of nucleotides in a DNA molecule dictate SEQUENCE of nucleotides in a DNA molecule dictate the amino acid SEQUENCE of polypeptidesthe amino acid SEQUENCE of polypeptides

DNA: Double Helix of Two Complementary Strands Held Together by H-Bonds

A GeneA Gene is a specific segment of a DNA molecule with is a specific segment of a DNA molecule with information for cell to make one polypeptideinformation for cell to make one polypeptide

DNA DNA ((transcribedtranscribed into single stranded RNA “copy”)into single stranded RNA “copy”)

!!

! !

mRNAmRNA (single stranded “copy” of the gene)(single stranded “copy” of the gene)

!!

!!

PolypeptidePolypeptide (mRNA message (mRNA message translatedtranslated into polypeptide) into polypeptide)

Genetic Information Flow: DNA to RNA to Protein

LipidsLipids: Fats, phospholipids, and steroids: Fats, phospholipids, and steroids

Diverse groups of compounds.Diverse groups of compounds.

Composition of Lipids:Composition of Lipids: C, H, and small amounts of O.C, H, and small amounts of O.

Functions of Lipids:Functions of Lipids: Biological fuelsBiological fuels Energy storageEnergy storage InsulationInsulation Structural components of cell membranesStructural components of cell membranes HormonesHormones

LipidsLipids: Fats, phospholipids, and steroids: Fats, phospholipids, and steroids

1. Simple Lipids1. Simple Lipids: Contain C, H, and O only.: Contain C, H, and O only.

A. A. FatsFats (Triglycerides). (Triglycerides). GlycerolGlycerol : : Three carbon molecule with three hydroxylsThree carbon molecule with three hydroxyls.. Fatty AcidsFatty Acids: : Carboxyl group and long hydrocarbon Carboxyl group and long hydrocarbon

chains.chains. Characteristics of fats:Characteristics of fats:

Most abundant lipids in living organismsMost abundant lipids in living organisms.. HydrophobicHydrophobic (insoluble in water) because nonpolar (insoluble in water) because nonpolar.. Economical form of energy storage (provide 2X the Economical form of energy storage (provide 2X the

energy/weight than carbohydrates).energy/weight than carbohydrates). Greasy or oily appearance.Greasy or oily appearance.

Fats (Triglycerides): Glycerol + 3 Fatty Acids

LipidsLipids: Fats, phospholipids, and steroids: Fats, phospholipids, and steroids

Types of FatsTypes of Fats

Saturated fatsSaturated fats: : Hydrocarbons saturated with H. Hydrocarbons saturated with H.

Lack -C=C- double bonds.Lack -C=C- double bonds. Solid Solid at room temp (butter, animal fat, lard)at room temp (butter, animal fat, lard)

Unsaturated fatsUnsaturated fats: : Contain -C=C- double bonds.Contain -C=C- double bonds. Usually Usually liquidliquid at room temp (corn, peanut, olive oils) at room temp (corn, peanut, olive oils)

Saturated Fats Contain Saturated Fatty Acids

2. Complex Lipids2. Complex Lipids: In addition to C, H, and O, : In addition to C, H, and O,

also contain other elements, such as phosphorus, also contain other elements, such as phosphorus,

nitrogen, and sulfur.nitrogen, and sulfur.

A.A. PhospholipidsPhospholipids: : Are composed of:Are composed of: GlycerolGlycerol 2 fatty acid2 fatty acid Phosphate groupPhosphate group

AmphipathicAmphipathic Molecule Molecule HydrophobicHydrophobic fatty acid “tails”. fatty acid “tails”. HydrophilicHydrophilic phosphate “head”. phosphate “head”.

FunctionFunction:: Primary component of the plasma Primary component of the plasma membrane of cellsmembrane of cells

Phospholipids: Amphipathic Molecules

In Water Phospholipids Spontaneously Assemble into Organized Structures

B.B. SteroidsSteroids: : Lipids with four fused carbon ringsLipids with four fused carbon ringsIncludes cholesterol, bile salts, reproductive, and adrenal Includes cholesterol, bile salts, reproductive, and adrenal

hormones.hormones. CholesterolCholesterol: : The basic steroid found in animals The basic steroid found in animals

• Common component of animal cell membranes.Common component of animal cell membranes.

• Precursor to make Precursor to make sex hormones (estrogen, sex hormones (estrogen, testosterone)testosterone)

• Generally only Generally only soluble in other fatssoluble in other fats (not in water) (not in water)

• Too much increases chance of Too much increases chance of atherosclerosis.atherosclerosis.

C. C. WaxesWaxes: : One fatty acid linked to an alcohol.One fatty acid linked to an alcohol. Very hydrophobic. Very hydrophobic. Found in cell walls of certain bacteria, plant and insect Found in cell walls of certain bacteria, plant and insect

coats. Help prevent water loss.coats. Help prevent water loss.

Cholesterol: The Basic Steroid in Animals