Lecture 5 Lecture 5 Sept 9, 2005Sept 9, 2005MACROMOLECULES #1MACROMOLECULES #1

Carbohydrates Carbohydrates

And LipidsAnd Lipids

-- Polymers Polymers

--CarbohydratesCarbohydratesmonomers and polymersmonomers and polymers

-- LipidsLipids

Lecture outline:Lecture outline:

Principles of Building Polymers:Principles of Building Polymers:

-- biological polymers are built from biological polymers are built from simple small unitssimple small unitscalled called monomersmonomers

-- addition of each addition of each monomericmonomeric unit occurs with theunit occurs with theremoval of a removal of a water moleculewater molecule

A A condensation dehydrationcondensation dehydration reactionreaction

-- ends are chemically distinct ends are chemically distinct directionalitydirectionality of synthesis of synthesis

-- requires requires energy inputenergy input for polymerization;for polymerization;uses carrier molecules to activate monomersuses carrier molecules to activate monomers

MODULAR DESIGN

SIMPLICITY AND VERSATILITYASSEMBLY-LINE MENTALITY

Don’t have to make every structure from scratch

Simplified chemistry, repeating link Dehydration Synthesis

DehydrationSynthesis

make bytaking water away

H-XXXX-OH H-YYY-OH H-ZZZZZ-OH

H-XXXX- YYY-ZZZZZ-OH

HOH HOH

Hydrolysisdeath by water

Monomers

Polymer

Endless variety of Polymers

Order of MonomersDifferent Amounts of each monomer

H-YYY-XXXX- ZZZZZ-OH

H-XXXX- ZZZZZ- YYY-OH

H-XXXX- YYY-ZZZZZ-OH

H-ZZZZZ- YYY-ZZZZZ-OH

• Monomers form larger molecules by condensation reactions called dehydration reactions

(a) Dehydration reaction in the synthesis of a polymer

HO H1 2 3 HO

HO H1 2 3 4

H

H2O

Short polymer Unlinked monomer

Longer polymer

Dehydration removes a watermolecule, forming a new bond

Figure 5.2A

• Polymers can disassemble by– Hydrolysis

(b) Hydrolysis of a polymer

HO 1 2 3 H

HO H1 2 3 4

H2O

HHO

Hydrolysis adds a watermolecule, breaking a bond

Figure 5.2B

Monomers PolymersCARBOHYDRATESCARBOHYDRATES

Sugars and Sugar DerivativesSugars and Sugar Derivatives

Monosaccharides Polysaccharides

Simple Sugars

GlucoseFructose

Ribose

storagestarch: amylose

amylopectinglycogen

structureFiber: cellulose

Monomers: Monomers: Polymers: Polymers:

Long chains of monomers

OligosaccharidesOligosaccharidesInformational structuresInformational structures

MONOSACCHARIDES = Carbohydrate Monomers

•1 Carbonyl - aldehyde or ketone R-C-H R1-C-R2

==O O

•All Other CARBONSeach have ONE alcohol group

R-OH

Expect them to be HYDROPHILICExpect them to be HYDROPHILIC

AldoAldosugarsugar

KetoKetosugarsugar

Triose sugars(C3H6O3)

Pentose sugars(C5H10O5)

Hexose sugars(C6H12O6)

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

HO C H

H C OH

H C OH

H C OH

H C OH

HO C H

HO C H

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

C OC O

H C OH

H C OH

H C OH

HO C H

H C OH

C O

H

H

H

H H H

H

H H H H

H

H H

C C C COOOO

Ald

oses

Glyceraldehyde

RiboseGlucose Galactose

Dihydroxyacetone

Ribulose

Ket

oses

FructoseFigure 5.3

Monosaccharides Vary in length3, 4, 5, 6 or 7 carbons

Carbon with Carbon with 4 different functional groups 4 different functional groups ChiralChiral or asymmetric carbonor asymmetric carbon = = “handed” carbon“handed” carbon

Also differ by Also differ by SPATIAL GEOMETRYSPATIAL GEOMETRY

RightRighthandedhanded

“D” form“D” form

LeftLefthandedhanded“L” form“L” form

StereoisomersStereoisomers not the same not the same

Plane Plane of of

symmetrysymmetry

Not Not chiralchiral

ChiralChiral

Not Not chiralchiral

ChiralChiral

ChiralChiral

ChiralChiral

Triose sugars(C3H6O3)

Pentose sugars(C5H10O5)

Hexose sugars(C6H12O6)

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

HO C H

H C OH

H C OH

H C OH

H C OH

HO C H

HO C H

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

H C OH

C OC O

H C OH

H C OH

H C OH

HO C H

H C OH

C O

H

H

H

H H H

H

H H H H

H

H H

C C C COOOO

Ald

oses

Glyceraldehyde

RiboseGlucose Galactose

Dihydroxyacetone

Ribulose

Ket

oses

FructoseFigure 5.3

Spatial Geometry yields a variety of forms

8 8 Forms!Forms!

5 and 6 Carbon Sugars CIRCULARIZE in WaterTo FORM RINGS

FischerFischerprojectionprojection

HaworthHaworthprojectionprojection

H

H C OH

HO C H

H C OH

H C OH

H C

O

C

H

1

2

3

4

5

6

H

OH

4C

6CH2OH 6CH2OH

5C

HOH

C

H OH

H

2 C

1C

H

O

H

OH

4C

5C

3 C

H

HOH

OH

H

2C

1 C

OH

H

CH2OH

H

H

OHHO

H

OH

OH

H5

3 2

4

(a) Linear and ring forms. Chemical equilibrium between the linear and ringstructures greatly favors the formation of rings. To form the glucose ring,carbon 1 bonds to the oxygen attached to carbon 5.

OH3

O H OO

6

1

Figure 5.4

Circularization causes another Circularization causes another chiralchiral carboncarbon

αα--DD--GlucoseGlucose ββ--DD--GlucoseGlucose

Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide.

Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose.Notice that fructose,though a hexose like glucose, forms a five-sided ring.

(a)

(b)

H

HO

H

HOH H

OH

O H

OH

CH2OH

H

HO

H

HOH H

OH

O H

OH

CH2OH

H

O

H

HOH H

OH

O H

OH

CH2OH

H

H2O

H2O

H

H

O

H

HOH

OH

O HCH2OH

CH2OH HO

OHH

CH2OH

HOH H

H

HO

OHH

CH2OH

HOH H

O

O H

OHH

CH2OH

HOH H

O

HOH

CH2OH

H HO

O

CH2OH

H

H

OH

O

O

1 2

1 41–4

glycosidiclinkage

1–2glycosidic

linkage

Glucose

Glucose Glucose

Fructose

Maltose

Sucrose

OH

H

H

Figure 5.5

monomeric sugars coupled together by

CONDENSATION REACTION

GlycosidicGlycosidicbondbond

Holds carbohydrates togetherHolds carbohydrates together

BreakdownBreakdownDoes notDoes notRequireRequireEnergyEnergyInputInput

SynthesisSynthesisRequires Requires EnergyEnergyInputInput

Sucrose (glucose+ fructose) Cane SugarLactose (glucose+galactose) Milk SugarMaltose (glucose+glucose) Beer

Dextran (short chain of glucose) Digested Starch

Furans (short chain of fructose) Onions

OligoSaccharides

DiSaccharides

Disaccharides, Oligosaccharides and Polysaccharides(two)(two) (few)(few) (many)(many)

Polysaccharides

•Long chains of Millions of monomers

•most common polymers made ONLY of GLUCOSE monomers

•Storage reserves: •Starch amylose• amylopectin, glycogen

•Structure: cellulose

Chloroplast Starch

Amylose Amylopectin

1 µm

(a) Starch: a plant polysaccharideFigure 5.6

MitochondriaGiycogen granules

0.5 µm

(b) Glycogen: an animal polysaccharide

Glycogen

Figure 5.6

Glycogen (or Glycogen (or AmylopectinAmylopectin))

Polysaccharides of glucose chains inPolysaccharides of glucose chains inan a(1an a(1-->4) linkage, with a(1>4) linkage, with a(1-->6) >6) branchesbranches

Structural Polysaccharides

•• CelluloseCellulose– Is also a polymer of glucose

– But has different glycosidic linkages than starch

– We can readily digest starchesbut cannot digest cellulose

• Cellulose is indigestable to animals– Cows and termites have microbes in

their stomachs to facilitate this process

Figure 5.9 (c) Cellulose: 1– 4 linkage of β glucose monomers

H O

O

CH2OH

HOH H

H

OH

OHH

H

HO

4

C

C

C

C

C

C

H

H

H

HO

OH

H

OH

OH

OH

H

O

CH2OH

HH

H

OH

OHH

H

HO4 OH

CH2OHO

OH

OH

HO41

O

CH2OH

O

OH

OH

O

CH2OH

O

OH

OH

CH2OH

O

OH

OH

O O

CH2OHO

OH

OH

HO4

O1

OH

O

OH OHO

CH2OHO

OH

O OH

O

OH

OH

(a) α and β glucose ring structures

(b) Starch: 1– 4 linkage of α glucose monomers

1

α glucose β glucose

CH2OH CH2OH

1 4 41 1

Figure 5.7 A–C

Starches:αα glycosidic linkage

OH “down”

Cellulose:ββ glycosidic linkage

OH “up”

Cellulose ß(1Cellulose ß(1-->4) linkage>4) linkageAmyloseAmylose a(1a(1-->4) linkage>4) linkage

Plant cells

0.5 µm

Cell walls

Cellulose microfibrilsin a plant cell wall

∩

Microfibril

CH2OH

CH2OH

OHOH

OO

OHOCH2OH

OO

OHO

CH2OH OH

OH OHO

O

CH2OHO

OOH

CH2OH

OO

OH

O

O

CH2OHOH

CH2OHOHOOH OH OH OH

O

OH OH

CH2OH

CH2OH

OHO

OH CH2OH

OO

OH CH2OH

OH

β Glucose monomer

O

O

O

O

O

O

Parallel cellulose molecules areheld together by hydrogenbonds between hydroxyl

groups attached to carbonatoms 3 and 6.

About 80 cellulosemolecules associate

to form a microfibril, themain architectural unitof the plant cell wall.

A cellulose moleculeis an unbranched βglucose polymer.

OH

OH

O

OOH

Cellulosemolecules

Figure 5.8

Polysaccharides Polysaccharides although although hydrophillichydrophillic

arearegenerally generally

Insoluble in waterInsoluble in water

--orders too much water around polymerorders too much water around polymer--Polymer tends to hydrogen bond to itselfPolymer tends to hydrogen bond to itself--Polymer falls out of solutionPolymer falls out of solution

Starch

““polymer effect”polymer effect”

Polymer forms Polymer forms Secondary StructuresSecondary Structures

Polymer hydrogen bonding Polymer hydrogen bonding to to Itself Itself

If If Denature Denature Secondary StructureSecondary Structure

(Break Hydrogen Bonds of Polymer with Itself)(Break Hydrogen Bonds of Polymer with Itself)

Water will Hydrogen bondWater will Hydrogen bondWith PolymerWith Polymer

RESULT IS BOUND WATERRESULT IS BOUND WATER GELGEL

Can FORCE polymer to stay Hydrated Can FORCE polymer to stay Hydrated Sugar Sugar DerrivativesDerrivatives

DisruptDisruptSecondary Secondary StructuresStructures--remain remain Hydrated!Hydrated!

Characteristics?Characteristics?

Some OtherSugar Derivatives or Modified Sugars

Missing one or more components:

a. 5 carbon RIBOSE andDEOXYRIBOSE

missing one alcohol

b. Glycerol - 3 Carbon Sugar withalcohol in place of an aldehyde

c. Sugar amines, Sugar acidshave amine or carboxylic acid group or something else in place of an alcohol

H - C - C - C - H- --

-- -H H H

OH

OH

OH

HHa.a.

b.b.

c.c.

Questions?Questions?

LIPIDSLIPIDShydrophobic characterhydrophobic character

Triglycerides Phospholipids Steroids

“Other”

FATSOILS-long termstorage depot

MEMBRANESMembranes

Hormones

Fatty Acids and Glycerol

Fatty Acid: carboxylic acid with LONG hydrocarbon chainF.A differ by:F.A differ by:

ChainChainlengthlength

saturationsaturation

• Fats– Are constructed from two types of smaller

molecules, a single glycerol and usually three fatty acids

(b) Fat molecule (triacylglycerol)

H HH H

HH H H H H H HH

H HHO

H O HC

C

C

H

H OH

OH

H

HH

HH

H H HH

H H H H HH

H

HCCCCCCCCC

CC

CC

CC C

Glycerol

Fatty acid(palmitic acid)

HH

H

H

H H HH

HH

HH

HH H H H

H H H

HHHHHHHHHHHHHHHH

H

H H H H H H H H H H H H H H HH

HHHHHHHHHHHHHH

H H H H H H H H H H H H H H HH

HHHHHHHHHHHHHHH

HO

OO

O

OC

C

C C C C C C C C C C C C C C C C C

C

CCCCCCCCCCCCCCCC

C C C C C C C C C C C C C C CO

O

(a) Dehydration reaction in the synthesis of a fatEster linkage

Figure 5.11

Triglycerides: 3 fatty acids

linked to Glycerolby CONDENSATION

SYNTHESIS

ESTER LinkageESTER Linkage

Properties in WaterProperties in Water

Insoluble !Insoluble !AllAll

hydrophobichydrophobic

TriglyceridesTriglycerides FATS OILSSolid Liquid

WHY?

SaturatedUnsaturated orPolyunsaturated

Like Fig 3-28

• Saturated fatty acids– Have the maximum number of hydrogen atoms

possible– Have no double bonds

(a) Saturated fat and fatty acid

Stearic acid

Figure 5.12Stack nicelyStack nicely

• Unsaturated fatty acids– Have one or more double bonds

(b) Unsaturated fat and fatty acidcis double bondcauses bending

Oleic acid

Figure 5.12

Do not Stack wellDo not Stack well

Free Fatty Acids

Hydrolyzed Triglycerides

PolarPolar(charged)(charged)HeadHead

Very Very HydrophobicHydrophobicTailTail micellemicelle

FattyFattyAcidsAcids

monolayermonolayer

amphipathicamphipathic

PhospholipidsPhospholipids

NonpolarPolar

Fatty acid tailsFatty acid tailsGl

ycer

ol

PhosphateHeadGroup

Fig 3-27Glycerol linked to 2 fatty acids

• Phospholipid structure– Consists of a hydrophilic “head” and

hydrophobic “tails”

CH2

OPO OO

CH2CHCH2

OO

C O C O

Phosphate

Glycerol

(a) Structural formula (b) Space-filling model

Fatty acids

(c) Phospholipidsymbol

Hyd

roph

o bic

tails

Hydrophilichead

Hydrophobictails

–

Hyd

roph

i lic

hea d CH2 Choline

+

Figure 5.13

N(CH3)3

PhospholipidPhospholipid Head GroupsHead Groups

HydrophillicHydrophillic! Polar groups! Polar groups

Phospholipid Phospholipid BilayerBilayer

Form Form BoundariesBoundaries

Hydrophilichead

WATER

WATER

Hydrophobictail

Figure 5.14

NonpolarNonpolar FA tailsFA tails

Polar Polar HeadgroupsHeadgroups

Polar Polar HeadgroupsHeadgroups3-D Ball (Sphere)

Vesicle or

Liposome Crosssection

Sheet

Inside

Outside

Hormones:Hormones:Signal moleculesSignal molecules

SummarySummary••Principles of Building PolymersPrinciples of Building Polymers

Directional assembly from simple unitsDirectional assembly from simple unitsRequires energy inputRequires energy inputCondensation dehydration reactionsCondensation dehydration reactions

••CarbohydratesCarbohydratesmonosaccharidesmonosaccharidespolysaccharidespolysaccharides

••LipidsLipidsTriglyceridesTriglyceridesphospholipidsphospholipidssteroidssteroids

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Nucleic AcidsNucleic Acids