BIOL 541: Lecture 10
25 Cards in this Set
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Carbohydrate Facts
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-Produced from CO2 and H2O via photosynthesis
-small as glyceradehyde (90g/mol) or big as amylopectin (200,000,000 g/mol)
-can be covalently linked to form glycoproteins and proteoglycans
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Carbohydrate Function
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-energy source and storage
-structural component o cell walls and exoskeleton
-informational molecules sin cell signaling
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Epimer
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2 sugars that only vary in the configuration around one carbon atom
-D-Glucose has two epimers
--D-Manose
--D-Galactose
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Ribose
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standard 5 carbon sugar
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Glucose
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standard 6 carbon sugar
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Fructose
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ketose form of glucose
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Aldehyde and Ketones are...
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electrophilic
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Alcohol oxygen atom is...
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nucleophilic
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Aldehydes or ketose attacked by alcohols...
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hemiacetals form
-Hemiketals form
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Cyclization of monosaccharides
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-pentose and hexose undergo this process
-old carbonyl carbon becomes new chiral center "Anomeric Carbon"
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Anomeric Carbon
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former carbonyl carbon after cyclization of monosaccharides
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pyranose
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6 membered oxygen-containing ring
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furanose
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5 membered oxygen containing ring
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Reducing agents
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aldehyde reduces (Cu2+ to Cu+) via fehling test
-aldehyde reduces (Ag+ to Ag0) via Tollens test
-allows for detection of glucose
-If free anomeric end in Acetal exists the sugar is a reducing agent
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Colorimetric Glucose Analysis
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-enzyme glucose oxidase catalyzes conversion of glucose to gluco-beta-lactone and hydrogen peroxide
-Hydrogen peroxide oxidizes organic molecules into colored compounds
-concentrations of compounds are measured colorimetrically
-determines amount of glucose present
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Glycosidic Bonds
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-Bonds two monosacc. together between an anomeric carbon and a hydroxyl carbon (reducing agent possible) or between an anomeric carbon and an anomeric carbon (no reducing agent possible)
-forms acetal from hemi-acetal
-hydrolized by acid but not base
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Polysaccharides
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-natural carbs are often polymers
-types
--homopolysaccharides
--heteropolysaccharides
--linear
--branched
-No defined MW unlike proteins because there is no template used to make polysaccharide
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Glycogen
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-branched homopolysaccharide of glucose
-functions as main storage polysaccharide in animals
-glycogen often form granules in cell that contain enzymes to synthesize and degrade
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Starch
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-mixture of 2 homopolysaccharides of glucose
--Amylose
--Amylopectin
-Main storage polysaccharide in plants
-starch often forms granules that contain enzymes to synthesize and degrade
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Amylose
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-component of starch
-unbranched polymer of (a1->4) linked residues
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Amylopectin
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-Component of starch
-branched w/ branch points w/ (a1->6) linkers every 24-30 residues
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Cellulose
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-branched homopolysaccharide of Glucose
-glucose monomers form (B1->4) linked chains
-H bonds between adjacent monomers and adjacent chains
-Most abundant polysaccharide in nature
-strucutre is tough and water-insouble (cotton nearly pure cellulose)
-Fungi, bacteria and protozoa secr…
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Chitin
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-linear homopolysaccharide of N-acetylglucosamine
-forms extended fibers similar to celllulose
-structure is tough but flexible, water insouble and indigestable
-cell wall in mushrooms and exoskeletons of insect, spiders, crabs
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Agar and Agarose
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-agarose is component of agar
-complex mixture of heteropolysaccharides containing modified glucose units
-cell wall in some seaweeds
-used in labs to grow bacteria
-agarose solutions form Gel used for DNA separation via electrophoresis
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Glycosaminoglycans
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-Linear polymer of repeating disaccharide units
-one monomer is either
--N-acetyl-glucosamine
--N-acetyl-galactosamine
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BIOL 541: Lecture 10