Macromolecules & Carbohydrates

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Macromolecules & Carbohydrates Lecture 3 Dr. Mamoun Ahram
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Macromolecules & Carbohydrates. Lecture 3 Dr. Mamoun Ahram. Cell's weight. Subunits. Subunits: the small building blocks (precursors) used to make macromolecules Macromolecules: large molecules made of subunits. Macromolecules. Carbohydrates (monosaccharides) Proteins (amino acids) - PowerPoint PPT Presentation

Transcript of Macromolecules & Carbohydrates

  • Macromolecules& CarbohydratesLecture 3Dr. Mamoun Ahram

  • Cell's weight

  • SubunitsSubunits: the small building blocks (precursors) used to make macromolecules

    Macromolecules: large molecules made of subunits

  • MacromoleculesCarbohydrates (monosaccharides)Proteins (amino acids)Nucleic acids (nucleotides)Lipids (fatty acids)

    Except for lipids, these macromolecules are also considered polymers

  • Relationship (monomers and polymers)

  • How water is removed?Mechanism 1: One subunit contributes an H and the other subunit contributes an OH

    Mechanism 2: One subunit contributes 2 H the other subunit contributes an O


  • ResourceThis lectureCampbell and Farrells Biochemistry, Chapter 16

  • What are they?Carbohydrates are polyhydroxy aldehydes or ketonesSaccharide is another name for a carbohydrate

  • Functions Source of energyStructure (cellulose and chitin)Building blocksCellular recognition

  • Classification IBy the number of sugars that constitute the molecule


  • MonosaccharidesBasic chemical formula: (CH2O)nThey contain two or more hydroxyl groups

  • Drawing sugarsFisher projections or perspective structural formulas



    Top (C1): Most highly oxidized C

  • Numbering carbonsagain

  • Numbering order of compounds with more than one functional groupCarboxylic acidAldehydeKetoneAlcoholAmineAlkyne = alkeneAlkane

  • Classification 2By the number of carbon atoms they contain


  • Trioses

  • GlyceraldehydeChiral carbon

  • Isomerism

  • Structural isomersSame number of atoms, different connectivity

  • StereoisomersSame number of atoms and connectivity, but not superimposable

  • Number of possible stereoisomers2n (n is the number of chiral carbons in a sugar molecule)

  • Isomers of glucose

  • Mirror images and non-superimposable, thenenantiomers

  • Light polarization

  • Sugar enantiomers (D- vs. L-)

  • Which one(s) is a chiral carbon?

  • Stereoisomers, but non-mirror images and non-superimposable, thendiastereomers OHOHHH

  • Diastereomers that differ in the orientation of one chiral carbonepimers

  • Isomerism

  • Formation of a ring structure

  • Ring structures

  • Example

  • Acetal/ketal vs. hemiacetal/hemiketalHemiacetal and hemiketal: ether and alcohol on same carbonAcetal and ketal: two ethers on same carbonWhat is the difference between hemiacetal and hemiketal and the difference between acetal and ketal?

  • Hemiacetal vs. hemiketal

  • Haworth vs. Fischer projections

  • Fischer vs. HaworthLeft-right vs. up-down

  • Anomers

  • vs fructose

  • - vs. -glucopyranose

  • Cyclic fructose

  • Cyclic aldohexoses

  • Cyclic ribofuranose


  • Sugar esters (esterification)What is the reacting functional group? Where does it react? What are the end products? Where are they used?

  • Sugar acids (oxidation)Where is it oxidized? What does it form?

  • Example 1

  • Example 2

  • Example 3

  • NoteOxidation of ketoses to carboxylic acids does not occur, but they can be oxidized because of formation of enediol form

  • Benedicts test

  • Sugar alcohols (reduction)What does it form?Examples include sorbitol, mannitol, and xylitol, which are used to sweeten food products

  • Deoxy sugarsOne or more hydroxyl groups are replaced by hydrogens

    An example is 2-deoxyribose, which is a constituent of DNA

  • N-glycosidesWhat is the reacting functional group? Where does it react? What are the end products? Where are they used?Examples: nucleotides (DNA and RNA)

  • Amino sugarsWhat is the reacting functional group? Where does it react? What are the end products? Where are they used?Further modification by acetylation

  • O-GlycosidesWhat is the reacting functional group? Where does it react? What are the end products? Where are they used?

  • Formation of full acetal

  • DisaccharidesWhat are disaccharide? Oligosaccharides? Hetero- vs. homo-?What is the type of reaction?What is a residue?Synthesizing enzymes are glycosyltransferasesDo they undergo mutarotation?Are products stable?

  • Distinctions of disaccharidesThe 2 specific sugar monomers involved and their stereoconfigurations (D- or L-)The carbons involved in the linkage (C-1, C-2, C-4, or C-6)The order of the two monomer units, if different (example: galactose followed by glucose)The anomeric configuration of the OH group on carbon 1 of each residue ( or )

  • Abundant disaccharidesConfiguration DesignationNaming (common vs. systematic)Reducing vs. non-reducing

  • vs fructose

  • Sucrose

  • Raffinose What are oligosaccharide?Example: raffinoseIt is found in peas and beansHomework

    What are the names of monosaccharides that make up raffinose?

    What is the monosaccharide that is attached to what disaccharide?

  • Oligosaccharides as drugsStreptomycin and erythromycin (antibiotics)Doxorubicin (cancer chemotherapy)Digoxin (cardiovascular disease)

  • PolysaccharidesWhat are polysaccharides?Homopolysaccharide (homoglycan) vs. heteropolysaccharides

  • Features of polysaccharidesMonosaccharides Length Branching

  • Storage polysaccharidesGlycogenStarchDextran

  • GlycogenWhich organisms? Which organs?

  • Structure

  • StarchWhich organisms?Forms: amylase (10-20%)amylopectin (80-90%)

  • Dextran A storage polysaccharideYeast and bacteria-(1-6)-D-glucose with branched chainsBranches: 1-2, 1-3, or 1-4


  • CelluloseWhich organism?Degradation?

  • Structural features? Why?

  • PectinWhat is the precursor?Where does it exist?

  • ChitinWhat is the precursor?Where does it exist?

  • GlycosaminoglycansWhat are they? Where are they located?Derivatives of an amino sugar, either glucosamine or galactosamineAt least one of the sugars in the repeating unit has a negatively charged carboxylate or sulfate group

  • Localization and function of GAG

    GAGLocalizationCommentsHyaluronatesynovial fluid, vitreous humor, ECM of loose connective tissuethe lubricant fluid , shock absorbingAs many as 25,000 disaccharide unitsChondroitin sulfatecartilage, bone, heart valvesmost abundant GAGHeparan sulfatebasement membranes, components of cell surfacescontains higher acetylated glucosamine than heparinHeparincomponent of intracellular granules of mast cells lining the arteries of the lungs, liver and skinA natural anticoagulantDermatan sulfateskin, blood vessels, heart valvesKeratan sulfatecornea, bone, cartilage aggregated with chondroitin sulfatesOnly one not having uronic acid

  • Bond orientationGlycosidic bonds in chondroitin 4-sulfate, hyaluronate, dermatan sulfate, and keratan sulfate are alternating (13) and (14) linkages

    Exception is heparin

  • ProteoglycansLubricantsStructural components in connective tissueMediate adhesion of cells to the extracellular matrixBind factors that stimulate cell proliferation

  • Bacterial cell wall

  • Peptidoglycan

  • Gram-positive vs. gram-negative bacteria

  • Why?Bacterial cell wall is composed of 1 or 2 bilayers and peptidoglycan shell Gram-positive: One bilayer and thick peptidoglycan outer shell Gram-negative: Two bilayers with thin peptidoglycan shell in between

  • How?Gram-positive: pentaglycine bridge connects tetrapeptides Gram-negative: direct amide bond between tetrapeptides

  • GlycoproteinsThe carbohydrates of glycoproteins are linked to the protein component through either O-glycosidic or N-glycosidic bondsThe N-glycosidic linkage is through the amide group of asparagine (Asn, N)The O-glycosidic linkage is to the hydroxyl of serine (Ser, S), threonine (Thr, T) or hydroxylysine (hLys)

  • Types of protein-linked sugarsGlucose (Glc)Galactose (Gal)Mannose (Man)Fucose (Fuc)N-acetylgalactosamine (GalNAc)N-acetylglucosamine (GlcNAc)N-acetylneuraminic acid (NANA)

  • Significance of protein-linked sugarsSoluble proteins as well as membrane proteinsPurpose:Protein foldingProtein targetingprolonging protein half-lifeCell-cell communicationSignaling

  • Blood typingThree different structures: A, B, and OThe difference:N-acetylgalactosamine (for A) Galactose (for B)None (for O)

  • Sialic acidN-acetylneuraminatePrecursor: the amino sugar, neuraminic acidLocation: a terminal residue of oligosaccharide chains of glycoproteinsEffect?