Carbohydrates Flashcards
Classify carbohydrates.
- monosaccharides
- disaccharides: 2 monosaccharides
- oligosaccharides: 3-10 monosaccharides
- polysaccharides: 11+ monosaccharides
Classify monosaccharides.
- according to no. of C atoms (3-7): trioses, tetroses, pentoses, hexoses, heptoses
-
according to functional group:
- aldoses (aldehyde), ketoses (ketone)
- reducing, non-reducing sugars
- polyols (only -OH)
How are cyclic monosaccharides formed?
Reaction type?
Consequence?
mutarotation via intramol. nucleophilic addition
→ hemiacetal/-ketal formed (alcohol + ald./ket. resp.)
⇒ chiral center at C1 → 2 anomers are formed, in equilibrium with open chain form
here: mutarotation of D-glucose shown
What are epimers?
Most important epimers of glucose?
isomers differing at the position of one -OH
epimers of glucose:
- mannose (at C2)
- galatose (at C4)
What is an anomer?
Which form is preferred in nature? Why?
epimer w/ different configuration at hemiacetal or hemiketal carbon (anomeric C1), formed by mutarotation
- α = down
- β = up
→ β preferred bc most stable when in equatorial position
Explain the optical activity of sugars.
Naturally occuring form of fructose, glucose?
light rotated either
- dextrorotatory (+), glucose in nature → dextrose
- laevorotatory (-), fructose in nature
What is D, L isomerism?
Which form is preferred in nature?
depends on orientation of -OH group on terminal alcohol C (C5 in glucose)
- D = dextro = right
- L = leavo = left
→ mostly D sugars in nature
What are pyranoses and furanoses?
- pyranoses = 6-membered ring
- furanoses = 5-membered ring
List and describe important physiological pentoses.
List and describe important physiological hexoses.
Which bonds/compounds are formed btw the -OH of the anomeric C of glucose and… ?
O-/N-glycosides
hemiacetal + -OH → acetal link
- if 2nd compound glucose → glucoside
- if 2nd compound galatose → galactoside
hemiacetal + -NH2 → N-glycosidic bond
What are amino sugars?
List some important N-acetyl derivatives.
Function?
sugar molecule in which a -OH group has been replaced with an -NH2 group
- D-glucosamine, D-galactosamine, D-mannosamine
- sialic acid
⇒ important components of glycoproteins, glycosphingolipids (blood group antigens), glycosaminogylcans
ex: D-glucosamine
Describe the general structure of sugar phosphate esters.
Examples.
Functions?
sugar + phosphate esterified (pretty obv lol)
- glucose-6-phosphate
- fructose-1t,6-bisphosphate
⇒ important intermediates of glycolysis and other processes of carbohydrate metabolism
List important reduced/oxidized monosaccharides.
Function?
reduction:
aldehyde/keto group reduced → prim./sec. alcoholic -OH group
- glucose/fructose → sorbitol (causes diarrhea)
oxidation:
- prim. -OH oxidized: uronic acid
- aldehyde oxidized: aldonic acid
- both terminal groups oxidized: aldaric acid
Which common disaccharides are non-/reducing?
- reducing sugars: maltose, lactose + other sugars w/ free glycosidic end
- non-reducing: sucrose
Explain the structure of starch.
What is the difference to glycogen?
α-glucosidic chain (glucosan), 2 constituents:
- amylose (20%): nonbranching, α-1-4 linkages
- amylopectin (80%): α-1-4 linkages, α-1-6 linkages at branches
glycogen same structure, but more highly branched
Explain the structure of cellulose.
β-D-glucose linked by β-1-4 bonds (cellobiose subunits)
→ insoluble fibers
Explain the structure of dextran.
Clinical relevance?
- *α-1,6 linkage**s between glucose +
- *α-1,3 linkages** that form branches
→ used as antithrombotic
Which components make up the ground substance for connective tissue?
How do they cushion other structures?
Examples?
proteoglycans = protein + glcusaminoglycan (amino sugars + uronic acids)
large no. of -OH groups/neg. charges → repulsion, keep carbohydrate chains apart
- hyaluronic acid
- heparin
What are glycoproteins?
Another name.
Function?
Examples.
also: mucoproteins = protein + oligosaccharide chains
→ important part of cell membranes (e.g. glycocalyx)
- fucose
- N-acetylneuraminic acid (sialic acid)
