BIOCHEM

exam 2

Common Monosaccharides

Aldose and Ketose (CH2O)n

Aldose

Carbonyl group at the end of Carbon chain

Ketose

Carbonyl group at any other position

Glucose Structure

D- Fructose

All monocaccharides (except dihydroxyacetone) contain

1+ chiral carbon atom

Reference Carbon

Chiral center most distant from the carbonyl carbon (determine D or L)

D-isomer

configuration at reference carbon is the same as D-Glyceraldehyde.

Epimers

Two sugars that differonly in the configuration around one carbon atom

Aldehydes and Ketones react with H2O to form

Hydrates

Aldehyde and Ketone + 1x alcohol

Hemi-acetal

Aldehyde and Ketone + 2x alcohol

Acetal /  Ketal

Acetal

Very stable and stay as acetal

Hemi-acetal

Highly reactive species

Intramolecular hemiacetal formation

Bulky group in eq position for it to stay in cyclic formation

In Aq solution

aldotetroses and monosaccharides with 5+ backbone carbon atoms occur as cyclic structures

Two cyclic forms of D-Glucose

alpha and beta

anomers

isomeric forms of monosaccharides that differ in their configuration about the hemiacetal/hemiketal carbon atom

anomeric carbon

carbonyl carbon atom

Haworth Persective Formula

Nomenclature for cyclics sugars

Pyranose and furanose

D-glucose formation

Favor pyranose.furanose because angle strain

Reducing sugars

Aldoses and suagrs that can form aldehydes

Red precipitate

Reducing sugar undergos a redox reaction where free aldehyde groups convert Cu2+ to Cu+ 

Ketoses = reducing sugar

tautomerize to aldehyde

Copper test assay

Blue = soluble

O-glycosidic bond

Covalent linkage joining two monosaccharides through condensation and hydrolysis and might form non-reducing sugar

Reducing end (hemi-acetal)

end of disaccharide or polysaccharide chain with a free anomeric carbon

Common disaccharides

1. Lactose = reducing

2. Sucrose = nonreducing 

3. Trehalose = nonreducing

reducing sugar

nonreducing sugars

more stable = longer shelf life

Polysaccharide

glycan

oligo«poly 

M_r > 20,000 without a defined length because enzyme will continusly link monosaccharides and not know when to stop polymerization. ( dependent on Temp, pH and number of monomers)

Homopolysaccaharide

Sinlge monomerric sugar species

Heteropolysaccharide

2+ kinds of monomers

Glycogen

• Energy storange molecular in animals

• Liver cells

• excess sugar (glucose→ glycogen)

• alpha 1→4

• alpha1→6 branches 

Starch

• Energy storage molecule in plants 

• contains:

  • amylose = long, unbranched chains of D-glucose connected by alpha 1→ 4  

  • amylopectin = larger polymer of alpha 1→ 4 and alpha 1→ 6

alpha 1→ 4 structure

6 residue turn helix

Cellulose

• tough, fibrous, water-insoluble, stable

• cell wall from plants 

• linear

• unbranched

• homopolysaccharide 

• D-glucose

• Beta 1 → 4 (animals dont have enxyme to hydrolyze) (most stable linear structure)

• Each chair is turned 180^.

• Stabilized by H-bonds

Chitin

• Linear

• homopolysaccharide

• N-acetylglucosamine

• Beta 1→4

• Acetylated amino groups = hydrophobic bc OH on regilar sugar are hydrophillic

Bacterial cell wall

• Gram (+) = 1 plasma membrane + 3 layers of peptidoglycan

• Gram (-) = 2 plsama membranes + 1 layer of peptidoglycan 

Peptidoglycan

• Polysaccharide cross-link = alternating copolymer of Beta 1→4- N -acetyl-D-glucosamine + N-acetylmuramic acid

• Peptide links L-Ala-D-Glu-L-Lys-D-Ala tetrapeptide

• Pentaglycine Cross-link by short peptides

Glycosaminoglycan

• Animal Cell composition

• Heteropolysaccharide in ECM (densely negative hydrophylic surface and attract Na+, growth factors and H2O) of cells

• Viscosicty, adhesiveness, tensile strength

• linear polyer of repeating disaccharide units linked through electrostatic interactions

Types of Glycosaminoglycans

• Hyaluranon (GlcA + GlcNAc)

• Keratan sulfate (Gal + GlcNAc65)

• Chondroitin 4-sulfate (GlcA + GalNAc4S)

• Heparin ( IdoA2S+ GlcNS3S6S) ( most negative charge)

• One monosaccharide is always either N-acetylglucosamine or N-acetylgalactosamine and the other is usually glucuronic acid or iduronic acid

• Contains sulfate groups 

Fatty acid

• Carboxylic acids with hydrocarbon chains from 4-36 carbons long

• Building block of fats

Oxidation of Fatty Acids

to CO2 and H2O is highly exergonic because hydrocarbon is highly reduced 

Nomenclature for Unbranched Fatty Acids

18:1(delta⁹)

chain length : double bonds (location)

Polyunsaturated Fatty Acids

• PUFA

• Contaons more than one = in their backbone

PUFAs and Humans

• must obtain alpha-linolenic acid (ALA;18:3(delta9,12,15)) from diet 

• humans use ALA to synthesize:

  • eicosapentaenoic acid (EPA; 20:5(delta5,8,11,14,17))

  • docosahexaenoic acid (DHA;22:6(delta 4,7,10,13,16,19))

Melting Point of Fatty Acids

@ room Temp:

• Saturated fatty acids = solid

• Unsaturated fatty acids are liquid 

Triacylglycerols =  fats = triglyceride

• Fatty acid esters of glycerol 

• 3 FA, each ester linkage with a single glycerol

  • simple ( one kind of FA)

  • Mixed ( 2/3 different FA)

• Non-polar, Hydrophobic 

• Store Energy and Insulation

  • adipocyte + seeds with lipases

Biological waxes

• esters of long-chain saturated and unsaturated FA + long = chain alcohols

• Energy storage 

Biological Membranes