Ch. 7 Flashcards
Common biological roles of carbohydrates
energy storage
metabolic intermediate
nucleic acids
structural
cell recognition
cell signaling
Common features of carbohydrates
(CH2O)n
chiral centers
linear and cyclic structures
glycosidic bonds
H-bond donors and acceptors
aldehyde containing sugar
aldose
ketone containing sugar
ketos
3 carbon sugar
triose
4 carbon sugar
tetrose
5 carbon sugar
pentose
6 carbon sugar
hexose
7 carbon sugar
heptose
How is stereochemistry assigned to sugars
bottom most chiral center orientation
D orientation
hydroxyl group on the right
L orientation
hydroxyl group on the left
Most common orientation of sugars in nature
D
Epimers
differ at one of several chiral centers
Constitutional isomers
differ in the order of attatchment
Enantiomers
Non superimposable mirror images
Diastereomers
Isomers that are not mirror images
Anomers
differ at asymmetric carbon in ring structure
5 membered ring sugar
furanose form
6 membered ring sugar
pyranose form
favored ring size of aldohexos sugars
pyranose form
favored ring size of aldopentos sugars
furanose form
favored ring size of ketohexos
furanose form
Oxidation at carbon 1 in aldos sugars
forms carboxylic acid (aldonic acid)
Oxidation at carbon 6
uronic acid
Oxidation ar carbons 1 and 6
aldaric acid
what is mutarotation
interconversion between open chain and α and β cyclic forms
What is a reducing sugar
contains an aldehyde or anomeric hydroxyl group that can be oxidized to carboxylic acid
What happens in deoxygenation
replace hydroxyl group with H or CH3
What is a Fehling test used for
Treat solution with Cu2+ to find aldehyde containing sugars through a red solid
Phosphate esters
replace hydroxyl group with a phosphate group (PO4)
Amino sugar
replace OH with NH2
Glycosidic bond
replace anomeric OH with OR or NH2
Consequence of forming glycoside
traps sugar in cyclic form
Disaccharides
2 sugars linked by glycosidic bond
Two roles of polysaccharides
energy storage and structure
3 types of energy storage polysaccharides
Starch, Glycogen, and Dextrans
Starch is made up of what?
α-amylose and amylopectin
α-amylose structure
linear chain of α1-4 linkage of D-glucose
amylopectin structure
linear chain of α1-4 linkage of D-glucose and α1-6 branches (every 12-30 units)
Glycogen structure
Similar to amlyopectin but more heavily branched
Benefits of heavily branched polymers
can be broken faster
Dextrans structure
linear chain of α1-6 linkage of D-glucose with braches
Two structural polysaccharides
Cellulose and Chitin
Structure of Cellulose
linear chain of β1-4 linkage of D-glucose
Structure of Chitin
similar to cellulose but with an acetamide at C2
α-amylase enzymatic role
hydrolyzes α1-4 linkages
cellulase enzymatic role
hydrolyzes β1-4 linkages
lactase enzymatic role
cleaves galactose and glucose β1-4 linkages
What are glycosaminoglycans
linear chains of repeating disaccharides with at least one charged group and an amino sugar
What is peptidoglycan
provides strength to bacterial cell walls
What are Glycoproteins
protein with covalently linked oligo- and polysaccharide groups
How are glycoproteins linked
O-linked (Ser, Thr, or hydroxylysine)
N-linked (Asn)
What effects to sugars have on a protein
can effect shape, solubility, location, and degradation
How is sialic acid used in degradation
As sialic acid is cleaved off, the protein can bind to a receptor better to be degraded
What are lectins
class of proteins that bind carbohydrates with high specificity and affinity
How to selectins directly help luekocytes
the leukocyte binds to the selectins to be directed towards the site of infection
common structural features of proteoglycans
extracellular protein
