1. Carbohydrates Flashcards
what is a carbohydrate made up of and what is the ratio
contains: carbonyl (C=O) and hydroxyl groups
=aldehydes or ketones with 2 or more hydroxyl groups
ratio of C,H,O is 1:2:1
can carbohydrates be 2C
no at least 3C etc
major classes of carbohydrates (4)
- monosaccharide (simple sugars)
-single aldehyde or ketone with hydroxyl - disaccharide
-2 units of monosaccharides - oligosaccharide
-short chains (3-10) monosaccharides - polysaccharide
-long chains/ more than 10 of monosaccharides
oligosaccharides may be linked to other macromolecules such as _____ and_____
glycoproteins & glycolipids
give 3 functions of carbohydrates
-store energy
-provide energy
-building blocks of macromolecules
-structural elements
-lipid metabolism
how to name monosaccharides based on number of carbons
sugar molecule –> “ose” at end of name
n=3 triose
n=4 tetrose
n=5 pentose
n=6 hexose
n=7 heptose
where do u start numbering carbons
end nearest the carbonyl group (C=O)
for ring: at carbonyl group
aldose vs ketose based on carbonyl
aldose = carbonyl on end (aldehyde)
ketose = carbonyl inside (ketone)
aldoses and ketoses are chiral?
YES - 4 different groups attached
what are constitutional isomers
same composition, different connectivity
how to get stereoisomers
2^power n
n=number of chiral centers
enantiomers vs diastereomers
enantiomers = non superimposable MIRROR images (must have AT LEAST one chiral center)
diastereomers = NOT mirror images ex.cis/trans
compare D and L enantiomers and how are they determined
D-sugars = OH group on the right
L-sugars = OH group on the left
-look at OH on whichever chiral carbon is farthest away from C=O
what is the penultimate carbon
highest numbered chiral carbon
where is carbon 1 drawn on a fischer projection
carbon #1 is always drawn ON TOP
what does it mean to be reduced
gain H (usually breaks C=O to become OH)
when could something no longer be distinguished as D or L sugars
if there is no longer a chiral carbon
what are epimers
-two sugars that differ only in the configuration around ONE CARBON
what are hemiacetals and hemiketals and what is special about their formations
hemiacetals = aldehydes attacked by alcohols
hemiketals = ketones attacked by alcohols
- new hemiacetal/hemiketal carbon becomes CHIRAL
alpha-anomer vs Beta-anomer
alpha - OH opposite C6
beta - OH same as C6
where is anomeric carbon
aldoses is C1
ketoses is C2
result of cyclization / on right side has OH / becomes chiral
what is haworth projection and how to draw
cyclic ring structure
- to the right in fischer projection = are on bottom of ring
-below attacking group (usually OH) = goes on top of ring
what is a furanose vs a pyranose
furanose = 5 membered ring
pyranose = 6 membered ring
which membered ring is more stable
6 membered ring = pyranose
what happens to pyranose at high temps
becomes furanose form ???
what are configurational isomers and example
interconvert thru BREAKING and re-forming covalent bonds
ex.alpha or beta
what are conformational isomers and example
interconvert WITHOUT BREAKING of covalent bonds
ex. endo or exo
what is meant by endo / exo
endo = same face (ex. both dash lines)
- C2 is on same side as C5
exo = opposite faces (one dash one solid line)
-C2 is on opposite side as C5
what is dehydration synthesis
monosaccharides linked by O-glycosidic bond and has removal of water
describe formation of glycosidic bond
AT LEAST ONE anomeric carbon is used for bond formation
what does it mean to be a reducing sugar
has a free anomeric carbon
are all monosaccharides and disaccharides reducing sugars?
monosaccharides - YES
disaccharides - NO only if have free anomeric carbon
how to name if reducing or non reducing
reducing - “ose”
nonreducing - “oside”
when to add “syl” to end of name of first molecule
if anomeric carbon is involved in glycosidic bond
could oligosaccharides have 1->1 linkages
no cuz has 3-10 monosaccharides linked and if had 1->1 then would not have a free anomeric carbon for 3rd to link to
homo vs heteropolysaccharide
homo - only one type of monosaccharide
hetero - more than one type of monosaccharide
what is the function of alpha glycosidic bonds
energy storage
what is the function of beta glycosidic bonds
structure
what are glucan homopolymers
contain only alpha-D-glucopyranose
starch
glycogen
cellulose
describe starch
energy storage for plants
amylose - linear (a1->4)
amylopectin - (a1->4 linkages and a1->6 branched linkages )
describe glycogen
energy storage in animals
(a1->4 linkages and a1->6 branched linkages )
describe cellulose
structural component of cell wall
BETA1->4 glycosidic bonds !
-linear
-each monomer is turned 180 relative to neighbor
describe chitin
BETA 1->4 linkages
-homopolysaccharide
-found in exoskeleton
what is most stable conformation of cellulose
straight extended chain
*hydrogen bonds between chains to promote sheets
