Carbohydrate structure and reactions Flashcards
What are 10 functions of carbohydrates?
Energy storage Energy source Structure Components of nucleotides Protection Lubrication Communication Information storage Mediation of cell adhesion and signalling Protein localization and activity
What is the general formula of a carbohydrate? What is n?
(CH2O)n. n is between 3 and 7
What functional group does every carbon in a sugar have?
Either a carbonyl or a hydroxyl
What is an aldehyde sugar called?
Aldose
What is a ketone sugar called?
Ketose
What are the 3 class sizes of sugars?
Monosaccharides, oligosaccharides, polysaccharides
What type of bond links sugars together?
Glycosidic bonds
Are monosaccharides water soluble?
Yes, usually
Are oligosaccharides water soluble?
Yes, usually
Are polysaccharides water soluble?
Not usually
What is a homopolysaccharide?
Polymer of only one sugar type
What is a heteropolysaccharide?
Polymer of multiple types of sugars
What are glyconjugates?
Sugars that are attached to other stuff, namely lipids and proteins
What is the most common number of carbons in a monosaccharide?
6
What is the smallest chiral sugar?
Glyceraldehyde
What carbon does numbering start at in a sugar ring?
The one closest to the carbonyl
How big do sugars need to be to cyclize in solution?
At least 4 carbons
How many stereoisomers are there with multiple chiral centres?
For n chiral centres, there’s 2^n stereoisomers
What determines if a sugar is D or L?
The configuration at the carbon farthest from the carbonyl compared to glyceraldehyde. The D isomer has the hydroxyl on that carbon pointing right
Are most naturally occurring sugars L or D?
D
What are epimers?
Sugars that differ in stereochemistry only at 1 carbon atom
What are enantiomers?
Molecules that are non-superimposable mirror images of each other
What are diastereomers?
Stereoisomers that aren’t mirror images
What happens to linear monosaccharides in solution?
They are susceptible to nucleophilic attack by alcohols to form hemiacetals or hemiketals
The hydroxyl on which carbon will attack the carbonyl in a hexose sugar?
Carbon 5
What happens to the carbonyl carbon when nucleophilic attack happens?
Becomes a hydroxyl that can point either up or down depending on the direction of attack
What type of linkage is formed when intramolecular cyclization occurs in a sugar?
Ether
What is the anomeric carbon?
The carbon that formerly had the carbonyl
What is the alpha anomer of a hexose sugar?
Carbon 6 and the OH on the anomeric carbon are on different sides
What is the stereochemistry of an alpha anomeric carbon if there is no carbon 6 hanging off the ring?
S
What is the beta anomer of a hexose sugar?
Both carbon 6 and the OH on the anomeric carbon are on the same side of the ring
What is the stereochemistry of a beta anomeric carbon if there is no carbon 6 hanging off the ring?
R
Is alpha or beta glucose more stable?
Beta
Why is beta glucose more stable than alpha glucose?
Has all the hydroxyls in equatorial positions
What is a 6 membered ring called?
Pyranose
What is a 5 membered ring called?
Furanose
What are 5 modifications of hexoses that can be made by substituting out a hydroxyl?
Oxidize to COOH Phosphorylation Deoxy sugars Amides Sialic acid
What is a reducing sugar?
A sugar that can reduce Cu2+
Are aldehydes able to be oxidized?
Yes, into COOH
Are ketones able to be oxidized?
No
Are aldoses or ketoses reducing sugars?
Aldoses
Is glucose a reducing sugar?
Yes
How does glucose testing for diabetes work?
Uses glucose oxidase and peroxidase to produce a coloured precipitate
What is hemoglobin glycation?
Non-enzymatic reaction between glucose and Hb, with glucose reacting with NH2 groups in Hb. More glucose in the blood means more glycated Hb
What happens to glycated hemoglobin?
Glycation causes rearrangements, oxidations, and dehydrations of hemoglobin, which makes it unusually reactive
What does a monosaccharide in solution become when it forms a glycosidic bond?
An acetal or ketal
What is a glycosidic bond?
A bond between any of the OH groups on one sugar and the anomeric carbon on the other sugar
What is an O glycoside?
The atom in the glycosidic bond is an O
What is an N glycoside? Where is this found?
The atom in the glycosidic bond is an N. Found in nucleotides and in sugars attached to asparagine
How do you name sugars?
Have the non-reducing end on the left, then figure out if the anomeric carbon is alpha or beta. Name the monosaccharide with the non-reducing end. Then identify the carbons in the glycosidic bond. Name the second monosaccharide. Continue for a longer chain
