carbs part 1 Flashcards
whats the carb general formula
Cm(H2O)n
what are carbs and what groups do they contain
hydrates of carbon though some contain other elements such as nitrogen
Synthesis by plants from CO2 & H2O + energy
they contain the carbonyl (C=O) and hydroxyl (OH) groups. which hydrogen bonds occur between
discuss alcohol solubility
Alcohols tend to be very soluble in water due to hydrogen bonding between water molecules and the polar OH groups.
name the 3 major carb groups
monosaccharide, oligosaccharide, and polysaccharide
monosaccharides NO. units and ex
they have 1 unit
e.g. ribose, glucose, fructose,
oligosaccharides unit NO. and ex
they have 2 or more units that don’t have to be same they can be different from each other
e.g. sucrose, maltose, lactose
polysaccharides NO. units and ex
they have many units (100 - 1000)
as poly means many
e.g. cellulose, starch, glycogen
what are the most common monosaccharides
pentoses (5 carbons) and the hexoses ( 6 carbons).
naming monosaccharides
Common names are used, ending in ‘ose’
what are monosaccharides classified as and how
Classified as aldoses or ketoses, depending on whether they contain an aldehyde or a ketone group.
what do stereoisomers have
multiple chiral carbons
in what shape are sugars found in nature
in a ring
in an aldose sugar what is attached to the first and last carbon
the first carbon is at top of chain and has an aldehyde group attached
the last carbon has the primary alcohol group attached (hydroxyl group)
how many chiral carbons does a hexose aldose sugar have
4
Therefore there are 2 to the power of 4 =16 stereoisomers , ie. 8 pairs of mirror images.
so 8 sugars
what does a chiral carbon have that a non chiral carbon doesn’t have
4 diff groups attached to the carbon
are ketoses rare or common in nature
rare.
fructose is the most interesting and common one
how many chiral carbons does a hexose ketose sugar have
3 chiral carbons …. Therefore there are 23=8 stereoisomers , ie. 4 pairs of mirror images.
what is D/L nomenclature is based on for
orientation of the hydroxyl group on the greatest number chiral Carbon, ex c6 on the aldose or ketose
as chiral carbons are numbered after the c=o group
D for right hand side
L foe left hand side
what are enantiomer optical isomers
non-superimposable mirror images of one another eg. D and L glucose
what are Diastereoisomer optical isomers
if not mirror images but their chiral carbons are connected to the exactly the same substrates but connected at differing configurations
what are epimer optical isomers
two diastereoisomers that differ only at one stereocenter eg. D-Arabinose and D-Ribose
what do cyclic forms result from
the intramolecular reversible reaction of their C=O group with an OH group (usually the OH on the highest numbered chiral carbon).
sugars in nature exist by large as a ring structure, as there most stable. But aren’t a ring structure in solution.
Its reversible reaction as ring opens and closes continuously but at very high speed
But theres always a time when we have a number of closed molecules at one time as they have to be in closed form in nature
Theyre intramolecular as it happens within the molecule
what forms when alcohol reacts with aldehydes and ketones
“hemi acetyls” or “hemi ketals”
what are pyranose form of a monosaccharide and furanose form
The pyranose form of a monosaccharide has a six-membered ring, while the furanose form has a five-membered ring.