Chapter 7- Carbohydrates Flashcards
What are oligosaccharides?
short chains of a few monosaccharide units
what are polysaccharides?
long chains of monosaccharide units
Monosaccharides have an ______ carbon chain with _____ carbons
unbranched
3-7
Monosaccharides are soluble in ____ but not _____
water
nonpolar solvent
two families of monosaccharides
aldose
ketose
Aldose characteristics
possess a carbonyl at the end of the carbon chain (aldehyde)
Ketose characteristics
carbonyl is found at any other position other than the end (is a ketone)
Carbons are numbered starting at the extremity closest to _____
carbonyl
Monosaccharides contain ________ centers
chiral
if there are n chiral centers then there are ____ stereoisomers
2^n
If OH on reference carbon is on the right it is known as ____ and in ___ configuration
Dextro
D
If OH on reference carbon is on left it is known as ____ and in ___ configuration
levo
L
Where is the reference carbon??
chiral carbon most distant from carbonyl
Monosaccharides with 5 or more carbons usually occur in solution as _____
cyclic (ring) structures
carb rings result from a reaction between ______ and _____
alcohols
aldehydes or ketones
An alpha anomer occurs when
OH is on opposite side of the CH2OH
A beta anomer occurs when
OH is on same side of the CH2OH
A pyranose ring is a
6 membered ring
a furanose ring is a
5 membered ring
How are hexoaldoses formed
OH on C5 attach C1 carbonyl which forms pyranose ring
when Hexoaldoses are formed, C1 becomes chiral making it an _____
anomeric carbon
when Hexoaldoses are formed, _____ becomes chiral making it an _____
C1
anomeric carbon
when ketohexoses are formed, _____ becomes chiral making it an _____
C2
anomeric carbon
How are ketohexoses formed?
OH on C5 attack ketone group on C2 which forms furanose ring
(6 member) Fisher to Haworth rules for C2, C3, and C4?
- If OH is right –> down
- If OH is left —> up
(6 member) Fisher to Haworth rules for C5?
- If OH is right –> D-sugrar- CH2OH is up
- if OH is left —> L-sugar- CH2OH is down
(6 member) Fisher to Haworth rules for C1?
- If alpha anomer has OH –> down (for D)
- If Beta anomer has OH —> up (for D)
The position of OH anomeric carbon by convention if alpha, is:
Alpha
Pyranose and furanose rings are not ____ but they may assume ______ conformation
planar
Boat or chair
Boat conformation is _____ stable than chair conformation for pyranose/furanose rings
Less
Interconvertion of cyclic a/b anomers in solution occurs via the ______ form
linear
Mixtures with pyranose/furanose rings contain a mixture of ______
alpha and beta forms
steps of carb ring converting from alpha to beta anomers
- ring opens into linear form
- close again to produce other anomer
A ______ bond joins monosaccharides to form oligosaccharides
O-glycosidic bond
product of O-glycosidic bond forming?
glycoside
Since the anomeric OH group is a/b, monosaccharides coming together form:
a or b glycosides
Glycosidic bonds result form the _____
condensation with an alcohol other than a sugar.
Which OH on the carb rings can form glycosidic bonds?
C1-C5
How to know when a sugar is a reducing sugar?
Any sugar counting a hemiacetal
Sugars with anomeric carbon not invloved in glycosidic bond are called _____
reducing sugars
Characteristics of reducing sugars
- Ring in equilibrium with linear form
- contain aldehyde (is reducing agent)
When anomeric carbon is involved in glycosidic bond, glycosidic bond renders sugar ____
Non reducing
Since the 2 anomeric carbons are involved in glycosidic bonds, Sucrose is not a _____
reducing sugar
since the anomeric carbon of glucose is free, lactose is a _____
Reducing sugar
