Chp 8 Carbohydrates

Carbohydrates are attached to proteins via

- O- glycosidic bonds to serine and threonine - N- glycosidic bonds to asparagine

GAGs

- linear polysaccharides consisting of a repeating disaccharide -normally an acetylated amino sugar alternating with a uronic acid -negatively charged -Heparin -Hyaluronate -Chodroitinns

Non Reducing Sugars

-Acetal/ Ketal -Cant mutarotate -wont react with Tollens, Benedicts, or Fehlings test

Carbohydrates

-Central in the matabolism of plants and animals -Provide nutritional energy

Proteoglycans

-Glycoproteins that have a bottlebrush shape and are glycosaminoglycans plus proteins -Polyanions and have a large overall negative charge -present in extracellular matrix and function as shock absorbers in connective tissue -glue between intracellular proteins and fibronectin

Mono/Di saccharides properties

-H-Bonding wiht themselves and water -solid at room temp -soluble in water -highly concentrated liquids are viscous

Amylopectin

-Has α(1-4) and α(1-6) linkages -Highly branched polymer that allows quick release of glucose -Homopolysaccharides -Component of starch -poor solubility in water

Glycosaminoglycans

-Highly negative charges -Heparin, Hyaluronic acid, and Chondroitin sulfate -Typically contains glucuronic acid, derivative acid -Present in many types of connective tissues -Contain D-N-acetylglucosamine

Starch and Glycogen

-Homopolymers of glucose -Amylose in unbranched -Amylopectin and Glycogen are branched α(1-6) -Stored intracellularly as insoluble grains -Both will give a positive test due to helical core shape

Chitin

-Homopolysaccharides -Contains N-AcetlyGlucosamine residues -Exoskeleton of crustaceans, insects, and spiders, cell walls of fungi -indigestible -Contains only β(1-4)

Reducing Sugars

-Maltose, Lactose, Fructose and N-acetyl muramic acid -Give positive Tollens test -React with a blue solution to give a brick red precipitate

D-Glucuronate

-Modified form of glucose where the hydroxymethyl is replaced with carboxylate -Comprise Hylauronic acid and chondroitin sulfates

Glycoproteins

-O-linked glycoproteins linked via serine, threonine, and hydroxylysine -N-linked glycoproteins linked via amide side chain of asparagines -Contain N-acetylneuraminic acid -Occur post-translationally and co-transitionally

Acid/Base Cat. Tautomerism

-Reversible -Occurs through enediol intermediate

Oxidation of Sugars with mild agents

-can open free aldehyde to form aldonic acids -CHO-> COOH -Reducing sugars

Oxidation of Sugars with strong agent

-can oxidize both aldehyde and primary oh group to carboxylic acids form= aldaric acid -enzymes can oxidize only primary OH group and leave aldehyde alone

Formation of Acetals and Ketals

-condensation -lose water -irreversible

Modified Hydroxyl Groups

-gives important derivatives like phosphorylation and phosphoester linkages

Proteoglycans

-glycoproteins whose carb. portions are linear, O-linked Glycosaminoglycans (GAGs ) -fill extracellular matrix (EM/ECM) or "decorate" cell membrane

Polysaccharides

-long chains of single sugars covalently linked -cellulose, glycogen, starch

Lactose

-non reducing Galactose β(1-4) Glucose

Lectins

-proteins that bind specific cell surface carbohydrates patterns -biological recognition involving cells and proteins

Maltose

-reducing Glucose α(1-4) Glucose

Cellobiose

-reducing Glucose β(1-4) Glucose

Reductions to Alditols

-reduction of C=O with NaBH4 -Makes them unable to cyclize

Oligosaccharides

-short chains of sugars -di, tri saccharides -covalently linked -sucrose, maltose, lactose

Monosaccharides

-single sugars -freely soluble -glucose, fructose

Starch

-storage polysaccharide -amylose and amylopectin

β-lactamases

-which hydrolyze β-lactam rings -destroy β-lactam antibiotics

Cellulose

-β(1-4) bonds -linear -Glucose as the only sugar residues present in the polymer -Animals cant digest it

Proteoglycans in ECM

bottlebrush shaped GAG is backbone protein makes up branches O linked GAGs

Syndecans

cell surface proteoglycans involved in signaling and regulation

Structural polysaccharides

cellulose

All monosaccharides besides dihydroxyacetone are

chiral

Amylose and Cellulose differ

due to Amylose glycosidic α(1-4) whereas Cellulose are β(1-4) bonds

D Glucose and L Glucose are

enantiomers

Anomerization

equilibrium between anomers through linear form

Subunit in the glycogen molecule is

glucose

D-Carbohydrates

have the same stereochemical configuration at the penultimate carbon atom position as that of D-glyceraldehyde

Flu Infection

hemagglutinin molecules have to dock to N-acetylneuraminic acid molecules on the surface of the host cell

lactone

intramolecular reaction between aldonic acids and alcohol to give a cylcic ester

Glycosidic Bond

joins glucose and fructose to form sucrose

Examples of Epimers

mannose and glucose galactose and glucose ribose and xylose

Hetero

multiple monomers

Homo

one monomer

Starch Phosphorylase

releases G1P happens more with more branching quickly releases glucose

Amino Sugars

replace the C 2' Oh with a NH2

Formation of Hemiacetal and Hemiketal are

reversible

Dextrin

small undigested branching then brokendown by dextrinase

Polysaccharides functions

storage structure recognition

Peptidoglycan

structural glyoconjugate β(1-4) bonds between NAM and NAG Murein

Starch is digested in

the small intestine and saliva by amylase

Glycogen

α(1-4) linkages α(1-6) linkages highly branched polysaccharide composed entirely of α-D-glucose units storage form of glucose

In the small intestine, starch is digested by

amylase into maltose

Bacter use lectin to

attach themselves to the host cell during infection

Influenza A

2 surface proteins -Hemagglutinin (HA) lectin -Neuraminidase (NA) enzyme

Carbohydrates have

4 kcal/g

Hemiacetal + Alcohol=

Acetal

Oligosaccharides are commonly found linked to protein through

Asparagine Serine Threonine

Carbs are attached to proteins through glycosidic bonds to

Asparagine Serine Threonine Hydroxylysine

Oligosaccharides units of glycoproteins are found covalently attached to

Asparagine Serine Threonine Hydroxylysine

Glycosaminoglycans exhibit the following properties

Attract and tightly bind cations Maintain the level of hydration in tissues

Glycoconjugates

Carb + (Lipid or Protein)

Hydrolysis product of cellulose

Cellobiose

Deoxy Sugars

Convert an OH to H at a specified location

Convert a carb from reducing to non reducing

Cyclization to the pyranose form and subsequent formations of a glycosidic bond with another carbohydrate via hydroxyl group at Carbon 1

Most carbohydrates naturally occur

D

Monosaccharides

D-Glucose and D-Galactose are epimers D-glucose and D-galactose are stereoisomers Normally exist in ringed forms Gluconate and Glucronate are formed by the oxidation of glucose

Commonly found carbohydrates in humans are stereochemically related to

D-Glyceraldehyde

______ is a ketose

D-fructose

Glycogen Phosphorylase

Degrades glycogen to form G1P

Glucose heated with an alkaline copper solution gives a positive Fehling's or Benedict's test for

Fructose, Mannose, and Glucose Copper precipitates Glucose oxidizes

Glycosaminoglycans

GAGs

Amylose Cellulose and Maltose are made up of

Glucose

Sugars that are epimers

Glucose and Galactose Glucose and Mannose Ribose and Xylose

Cleavage of glucose from the non reducing ends of glycogen chains is done by

Glycogen Phosphorylase

Why does starch give a positive iodine test?

Helical shape of core

Alcohol + Aldehyde =

Hemiacetal

Alcohol + Ketone =

Hemiketal

______ isnt a polymer of glucose

Heparin

______Contributes to water binding properties of proteoglycans

Highly charged space between the core proteins and hyaluronate

Amylose

Homopolysaccharide of glucose α(1-4) bonds one reducing end component of starch poor solubility in water

Hemiketal + Alcohol=

Ketal

Hydrolysis product of starch

Maltose

These are hydrolyzed by enzymes of human origin within the GI tract

Maltose Lactose Amylose

Carbohydrate portion of plasma membrane

Oriented asymmetrically in bilayers Confer a negative charge to the cell surface Can attach to proteins and lipids

Main component of bacterial cell walls

Peptidoglycan

Maltose, Cellobiose, Lactose, and Dextrin

Reducing Sugars

Proteoglycans found in Connective Tissue are

SHOCK ABSORBERS

Carbohydrates is covalently bound to serum glycoproteins through

Serine Asparagine

Amino Acids involved in either N or O glycosidic linkages

Serine (S) Threonine (T) Asparagine (N) Hydroxylysine

Polysaccharides in biological systems may

Serve as a storage form of energy enhance the hydration of tissues serve as extracellular structural elements

Sucrose and Lactose differ in

Standard free energy of hydrolysis of the glycosidic bonds Ability to reduce cupric ion complexes

Major Functions of Polysaccharides

Storage form of energy Structural Components of membranes Structural elements of the extracellular matrix Signaling molecules in biological membranes

Epimers

Subset of diastereoisomers when 2 sugars differ only in the configuration around 1 carbon

Glycoproteins, the first sugar will link to the peptides to form a glycosidic bond with

Threonine, Asparagine, and Serine

Testing Reducing Sugars

Tollens Test Benedicts Test Fehlings test -create a brick red precipitate

Anomers

Whether a ring is α or β