The simplest aldose sugar, __ has __ chiral center(s)
glyceraldehyde (3 C’s); 1
(See slide #2)
The simplest ketose sugar, __ has __ chiral center(s)
Dihydroxyacetone (3 C’s); 0 (achiral)
(See slide #2)
A reaction between __ results in a hemiacetal
an aldehyde (C1) & an alcohol (C5)
(during the cyclization of an aldohexose such as glucose. See slide #3)
Glucose has ___ stereoisomers in Fischer form & __ stereoisomers in Haworth form
2^4 = 16 stereoisomers;
2^5 = 32 stereoisomers
(See slide #2 & 3)
In alpha, the anomeric OH is __ to CH2OH in a pyranose. In beta, the anomeric OH is __
trans (or axial when in chair conformation); cis (or equatorial when in chair conformation)
(See slide #3)
Epimers & their OH positioning
Epimers differ at the positioning of the OH group at one chiral carbon. Remember 2-3-4-MAG
Mannose (epimer @ C2)
Allose (epimer @ C3)
Galactose (epimer @ C4)
(See slide #4)
A reaction between __ results in a hemiketal
a ketone (C2) & an alcohol (C5)
(during the cyclization of a ketohexose such as fructose. See slide #6)
In both D-glucopyranose & D-fructofuranose, which is more stable? In alpha or beta form?
beta (less steric clash)
Fructose has __ stereoisomers in Fischer form & __ stereoisomers in Haworth form
2^3 = 8 stereoisomers;
2^4 = 16 stereoisomers
reducing sugars
has a free OH in its anomeric carbon
can mutarotate
will produce a positive Benedict’s or Tollens test
In the Tollens & Benedict’s reagent test, what is being oxidized & what is reduced?
The sugars are oxidized & the metals are reduced
What does a positive & negative Benedict’s test look like?
Negative: blue
Positive: copper color precipitate (since copper is the metal used)
What does a positive & negative Tollens test look like?
Negative: clear
Positive: silver precipitate (since silver is the metal used)
non-reducing sugars
glycosides
CANNOT mutarotate
will produce a negative Benedict’s or Tollens test
What does a Maltose structure look like? (Need to know how to draw)
2 Glucoses with a 1-4 glycosidic linkage
(See slide #8)
How many stereoisomers does a disaccharide have (in Haworth form)?
2^(10 chiral centers) = 1024 stereocenters
5 chiral centers for each sugar. See slide #8
What does a Lactose structure look like? (Need to know how to draw)
a Galactose + a Glucose with a 1-4 glycosidic linkage
(See slide #8)
concept of a sugar glycoside
when an anomeric carbon of one sugar reacts with the anomeric carbon of another sugar (hence no free anomeric OH groups)
when an anomeric OH is transformed into an OR
(See Ex. 2 on slide #11)
Branched carbohydrate polymer found in animals
Glycogen
Note: All other carbohydrate polymers are found in plants. The one whose structure is exactly like Glycogen is Amylopectin. The other 2 are not branched.
(See table on slide #12)
Branched carbohydrate polymer found in plants
Amylopectin
Note: Amylopectin’s structure is exactly the SAME as Glycogen.
(See table on slide #12)
Non-branched carbohydrate polymer that has alpha1-4 as the main chain
Amylose
(Also has a helical shape but won’t show that in a 2D structure)
(See table on slide #12)
Non-branched carbohydrate polymer that has beta1-4 as the main chain
Cellulose
Note: All other carbohydrate polymers have alpha1-4 as the main chain
(See table on slide #12)
Functions of carbohydrate polymers
Glycogen, Amylopectin, & Amylose: energy storage
Cellulose: structural support
glycosidic linkage of the branch of carbohydrate polymers
alpha1-6
(Occurs in branches of Glycogen & Amylopectin. See slide #13)