14 - Carbohydrates Flashcards
What is the most abundant biomolecule in nature?
Carbohydrates
What are four cellular functions of carbohydrates? (broadly)
Energy
Structure
Communication
Precursor for other biomolecules
Carbohydrates are a direct link between ____ and ____
Solar energy and chemical bond energy
What is the most basic component of a carbohydrate (eg. the lowest molecular formula)
Can be thought of as a carbon and H2O (CH20)
What is a monosaccharide
Aldehyde or ketone derivatives of straight chain polyhydroxyalcohols containing a minimum of 3 C atoms
How can different monosaccharides be differentiated?
By their carbonyl functional group (eg. aldehyde or ketone, aldoses and ketoses)
Or by number of C atoms (eg. triose, nonose etc.)
Put together you can have things like aldotrioses
monosaccharides are also in D or L forms (stereoisomers), the D form is much more common than L.. By convention the assymetric carbon most distal from the carbonyl group (O=C-H) gives the D or L notation.
What are the names of carbohydrates with different C numbers? (3 to 9)
A hint, ribose is a pentose
Triose tetrose pentose hexose heptose nonose
What is the organic chem equivalent for D and L in monosaccharides?
D = R L = S (think left)
What is the difference between enantiomer and diastereomer monosaccharide stereoisomers?
Enantiomers are exact mirror images shown in Fischer diagrams, diastereomers are not complete mirror images.
What are epimers?
Stereoisomers that differ in arrangement at a single chiral carbon. An example is D-glucose and D-galactose. D-mannose is a epimer to D-glucose as well, but not to D-galactose
How do cyclic monosaccharides occur and what are two types are made?
When a hydroxyl group in a sugar reacts with the aldehyde or ketone groups. They form either:
hemiacetals (aldehyde + OH)
hemiketals (ketone + OH)
What is the anomeric carbon atom?
It’s the chiral carbonyl carbon in a cyclic sugar. The anomeric carbon can either be α or β, depending on if the hydroxyl group is on the right/down (R) or the left/down (L)
On Haworth structures (showing ring as 2D, not 3D like in conformational structures) the hydroxy group is down in α and up in β
What kind of rings are formed in monosaccharide cyclization? (2 types)
All rings have an oxygen in them, the carbon clockwise of the oxygen is the 1’ anomeric carbon.
Furan rings have 5 members (4 C and 1 O)
Pyran rings have 6 members (5 C and 1 O)
The monosaccharide names for these two types are furanose and pyranose
Converting linear depiction of cyclical sugars to cyclical.
The whole thing ‘timbers’ down, but there’s a catch, groups depicted on the right point up and groups depicted on the left point down.
Conformation of the pyranose rings
The pyranose ring is like a cyclohexane except it hase an O instead of a 5’ C. It can be in boat or chair conformation, if the substituents are in certain position, steric crowding can occur in the boat position.
