Carbohydrates Struc and Functions Flashcards
How are Carbohydrates formed?
-Produced from CO2 and H2O via photosynthesis in plants
Name some functions which carbohydrate
- energy source and energy storage
- structural component of cell walls and exoskeletons
- informational molecules in cell-cell signaling
If carbohydrates are linked with protein what do we get?
-Can be covalently linked with proteins to form:
glycoproteins and proteoglycans
structure: What are alkyl halide? What are amine? What are ether? What are aldehyde?
What are amide?
- CX (X= F,Cl, Br, I)
- CNH2
- COC
- COH (double to O, H connected to C)
- CONH2 (double to O, NH2 connected to C)
What does R and S characterize in Cahn-Ingold-Prelog Convention?
-R and S characterize the absolute configuration characterize the absolute configuration of a specific stereocenter, not a whole molecule
-R - rectus - right
S - sinister - left
-have to draw a cercial from the most priority (atom mass) to lowest
->Only the chiral carbon (is a carbon atom that is attached to four different types of atoms or groups of atoms) that is most distant from the carbonyl carbon is designated as D (right) or L (left)
Which functional group does aldose contain? Which functional group does ketone contain?
- An aldose contains an aldehyde functionality
(s. a. Glyceraldehyde (aldotriose)) - A ketose contains a ketone functionality
(s. a. Dihydroxyacetone (ketotriose))
What are enantiomers?
-Stereoisomers that are non-superimposable mirror images
(nicht übereinander spiegelbar)
-s.a. D and L isomers of a sugar are enantiomers
For example, L and D glucose have the same water solubility
Are most hexoses and simple sugars L or D form?
- Most hexoses in living organisms are D stereoisomers
- Some simple sugars occur in the L-form, such as L-arabinose
What do horizontal bonds show in Fischer projections?
- Horizontal bonds are pointing toward you
- vertical bonds are projecting away from you
What are diastereomers?
- stereoisomers that are not mirror images
- >have different physical properties
What are epimers?
-Epimers are two sugars that differ only in the configuration around one carbon atom
Which structure are to know?
- Ribose is the standard five-carbon sugar
- Glucose is the standard six-carbon sugar
- Galactose is an epimer of glucose (epimer at C-4)
- Mannose is an epimer of glucose (epimer at C-2)
- Fructose is the ketose form of glucose
What are hemiacetals and hemiketals?
- Aldehyde and ketone carbons are electrophilic
- Alcohol oxygen atom is nucleophilic
- When aldehydes are attacked by alcohols, hemiacetals form
- When ketones are attacked by alcohols, hemiketals form
Pentoses and hexoses undergo which process? Describe the process
- they readily undergo intramolecular cyclization
- The former carbonyl carbon becomes a new chiral center, called the anomeric carbon
- The former carbonyl oxygen becomes a hydroxyl group
How is the anomer determined to be alpha or better?
- If the hydroxyl group is on the opposite side (trans) of the ring as the CH2OH moiety the configuration is α
- If the hydroxyl group is on the same side (cis) of the ring as the CH2OH moiety, the configuration is β
What are pyranoses, furanoses? What is an anomeric carbon; where is it drawn?
- Six-membered oxygen-containing rings are called pyranoses
- Five-membered oxygen-containing rings are called furanoses (4erC, ein O im Ring)
- anome ist ein Chiralitätszentrum ,The anomeric carbon is usually drawn on the right side
How does the chain-ring equilibrium look like?
-ring form on one side and open chain form (linear) on the other side
Which tests can help with the detection of reducing sugar?
- Aldehyde can reduce Cu^2+ to Cu^1 (Fehling’s test)
- Aldehyde can reduce Ag^1 to Ag^0 (Tollens’ test)
How does the colorimetric glucose analysis work?
- enzymatic methods are used to quantify reducing sugars such as glucose
- The enzyme glucose oxidase catalyzes the conversion of glucose to glucono-δ-lactone and hydrogen peroxide (H2O2)
- Hydrogen peroxide oxidizes organic molecules into highly colored compounds
- Concentrations of such compounds is measured colorimetricall
Where is the colorimetric glucose analysis used?
-Electrochemical detection is used in portable glucose sensors
Name important Hexose Derivates
- go to:
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Give the abbreviations for :
Abequose, arabinose, fructose, fructose, galactose, glucose, mannose, rhamnose, ribose, xylose, glucuronic acid, galactosamine, glucosamine, N-acetylgalactosamine, n-acetylglucosamine, iduronic acid, muramic acid, N-acatylmuramic acid, N-acetylneuraminic acid
-abe, ara, fru, fuc, gal, glc, man, rha, rib, xyl, GlcA, GalN, GlcN, GalNAc, GlcNAc, IdoA, mur, Mur2Ac, Neu5Ac
How is an acetal produced?
- reaction of a hemiacetal with an alcohol in acidic solution
Between which two carbons can a glycosidic bond occur?
- Two sugar molecules can be joined via a glycosidic bond between an anomeric carbon and a hydroxyl carbon
- bewteen two anomeric carbons
Which is less reactive:
-glycosidic bond (an acetal) between monomers or the hemiacetal at the second monomer?
- glycosidic bond (an acetal) is less reactive
- > Second monomer, with the hemiacetal, is reducing
- > Anomeric carbon involved in the glycosidic linkage is nonreducing
What is maltose?
-The disaccharide formed upon condensation of two glucose molecules via 1 → 4 bond is called maltose
What does the product of two anomeric carbons joined together with a glycosidic bond have?
- The product has two acetal groups and no hemiacetals
- >There are no reducing ends, this is a nonreducing sugar
How is Lactose created?
How is Sucrose created?
How is Trehalose created?
Lactose:
-b-d-galactopyranosyl (1->4)-b-d-glucopyranose
Sucrose:
-b-d-fructofucanosyl (1->2) a-d- glucopyranoside
-a-d-glucopyranosyl (1->1) a-d-glucopyranoside
How are natural carbohydrates usually found?
-found as polymers
What can these polysaccharide (polymers) be?
- homopolysaccharides
- heteropolysaccharides
- linear
- branched
What do polysaccharide not have? (in contrast to proteins)
- Polysaccharides do not have a defined molecular weight
- >no template (Vorlage) is used to make polysaccharides
Difference between heteropolysaccarides and homopolysaccharides?
-heteropolysaccharides consist of two or more monomer types homo does not
What is glycogen?
- is a branched homopolysaccharide of glucose
- > storage (polysaccaride) form of glucose (for animals) (needed for transport to cells)
- > weight reaches several millions
Where are linked chains + branching points in glucose?
- Glucose monomers form (α1 → 4) linked chains
- Branch-points with (α1 → 6) linkers every 8–12 residues
What is starch (Stärke)?
-s a mixture of two homopolysaccharides of glucose
Which two types of starch exists in plants?
- Amylose is an unbranched polymer of (α1 → 4) linked residues
- Amylopectin is branched like glycogen but the branch-points with (α1 → 6) linkers occur every 24–30 residues
- > Molecular weight of amylopectin is up to 200 million
- > main storage polysaccharide in plants
What do glycogen and starch form in metabolism? What do they contain?
- often form granules in cells
- Granules contain enzymes that synthesize and degrade these polymers
- Glycogen and amylopectin have one reducing end but many nonreducing ends
- Enzymatic processing occurs simultaneously in many nonreducing ends
What is cellulose?
- Cellulose is a branched homopolysaccharide of glucose
- Glucose monomers form (β1 → 4) linked chains
- > linear structure (unlike starch and glycogen)
Which bond occurs in cellulose and what is the result?
- Hydrogen bonds form between adjacent monomers
- Additional H-bonds between chains
- Structure is now tough and water-insoluble (wasserunlöslich)
What is the difficulty with the cellulose metabolism?
- The fibrous structure and water-insolubility make cellulose a difficult substrate to act on
- > Most animals cannot use cellulose as a fuel source because they lack the enzyme to hydrolyze (wasserspaltung) (β1 →4) linkages
Which role does cellulase take if it comes to ruminants, fungi, bacteria?
- Fungi, bacteria, and protozoa secrete (ausscheiden) cellulase, which allows them to use wood as source of glucose
- Ruminants and termites live symbiotically with microorganisms that produces cellulase
What is the structure of Chitin made of?
- is a linear homopolysaccharide of N-acetylglucosamine
- N-acetylglucosamine monomers form (β1 → 4)-linked chains
Describe the properties of Chitin
- Forms extended fibers (Fasern) that are similar to those of cellulose
- Hard, insoluble, cannot be digested (verdaut) by vertebrates (Wirbeltire)
- Structure is tough but flexible, and water-insoluble
Where is Chitin found?
-Found in cell walls in mushrooms, and in exoskeletons of insects, spiders, crabs, and other arthropods
What is glycosaminoglycans made of? What can one monomer be?
-is a Linear polymers of repeating disaccharide units
-monomer:
-N-acetyl-glucosamine or
-N-acetyl-galactosamine
are also modified to contain negatively charged groups:
-Uronic acids (C6 oxidation)
-Sulfate esters
What do glycosaminoglycans form with fibrous (faserig) proteins?
- form extracellular matrix
- > connective tissue (Gewebe)
- > Lubrication of joints (Gelenke)
Name types of glycosaminoglycan
-Hyaluronate (50000 disaccharides) (GlcA- (B1-3) GlcNAc (B1-4)
-Chondroitin 4-sulfate (20-60) (GlcA (B1-3) GalNac4S (B1-4)
-Keratan sulfate (25)
(Gal (B1-4) -GlcNAc6S) (B1-3)
-Heparin (15)
IdoA2S (a1-4) GlcNS3S6S (a1-4)
Name the roles of starch, glycogen, cellulose, chitin, dextran, peptidoglycan, agarose, hyaluronan (a glycosaminoglycan)
- starch-> energy storage in plants
- glycogen: energy storage in bacteria and animal cells
- cellulose: in plants gives rigidity (steifheit) and strength to cells
- chitin: in insects, spiders, gives rigidity and strength to exoskeletons
- dextran: in bacteria, gives rigidity and strength to cell envelope
- agarose: in algae, cell wall material
- hyaluronan: in vertebrates, extracellular matrix of skin and connective tissue; viscosity and lubrication in joints
What is glycoprotein?
- a protein with small oligosaccharides (small number of sugar) attached
- > carbohydrate attached via it anomeric carbon on protein
Where do carbohydrates play a role in? (reco)
-protein- protein recognition
With what do viral proteins heavily glycosylated help?
-evade (umgehen) the immune system
Which two types of linkages exist in Glycoprotein?
oligosaccharides might be attached to protein
-O linkage:
via the oxygen atom on the side chain of threonine or serine
-N linkage:
via nitrogen atom (NH) on the side chain of asparagin
How is proteoglycan constructed?
-Sulfated glucoseaminoglycans attached to a large rod-shaped protein in cell membrane
What are syndecans, and glypicans?
- Syndecans: protein has a single transmembrane domain
- Glypicans: protein is anchored (verankert) to a lipid membrane
What is the function of articular cartilage (Gelenkknorpel) within a joint?
- reduce friction
- load balancing (Lastverteilung)
What is extracellular matrix (ecm) ? The role? Main components
-Material outside the cell
-Strength, elasticity, and physical barrier in tissues
-Main components:
Proteoglycan aggregates
Collagen fibers
Elastin (a fibrous (faserig) protein)
What are some integral membrane proteins?
- some are proteoglycans
- > syndecans
- other are receptors for extracellular proteoglycans
- > integrins
What do the proteins regulate by transmitting signals into the cell?
- cell growth
- cell mobility
- apoptosis (genetisch programmierter Zelltod, der für die Entwicklung vielzelliger Organismen notwendig ist)
- wound healing
