CH 460
Dr. Muccio
Worksheet 4
What is the difference between an aldose and a ketose?
Aldoses have the aldehyde functional group at C-1 and ketoses have a ketone
function group at C-2.
What is the oxidation number of the carbon on the following 3 groups?
From left to right: 0, 1, -1.
Circle the carbons in the figure below that are chiral. How many isomers does this
molecule have?
The middle two should be circled. There are 22 = 4 isomers.
What is the difference between an epimer and an enantiomer?
Epimers are two different molecules where only 1 chiral center is different. In
enantiomers, all chiral centers are different.
How is the Fisher projection of D-glucose converted to L-glucose?
L has the OH on the left (remember L for “L”eft), D has the OH on the right in a
Fisher projection with the most oxidized carbon on the top. You must switch
the positions (all D’s become L’s and vice versa) of all chiral carbons.
D is the default carb (remember: your body can only “D”igest “D” carbs). The
name comes from the stereochem of the last chiral carbon. If it’s L, it’s an L
carb and vice versa.
To convert from straightchain to the Haworth projection, remember
“DOWNright UPlefting” (like ‘this is downright uplifting!’). The OHs that are on
the right of the straight chain will point down, and OHs that are left will be up.
The chemical formula of a tetrose monosaccharide is _____.
C6H12O6
C4H10O4
C6H10O4
C4H8O4
None
CH 460
Dr. Muccio
Worksheet 4
Match the carbohydrates to their descriptions on the left.
D-Glyceraldehyde ___D__
D-Threose __H___
D-Ribose ___C__
D-Mannose ___A__
D-Galactose ___G__
D-Erythrose ___B__
D-Xylose __F___
D-Glucose ____E_
D-Arabinose ___I__
D-Fructose __N___
D-Xylulose __K___
D-Erythrulose __M___
Dihydroxyacetone __J___
D-Ribulose __O___
L-Mannose ___L__
A. C-2 Epimer of Glucose
B. C-2 Epimer of Threose
C. Pentose with D,D,D stereochem
D. Triose
E. Hexose with DLDD stereochem
F. C-3 Epimer of Ribose
G. C-4 Epimer of Glucose
H. C-2 Epimer of Erythrose
I. C-2 Epimer of Ribose
J. Ketose of Letter D
K. Ketose of Letter F
L. Enantiomer of Letter A
M. Ketose of Letter B
N. Ketose of Letter E
O. Ketose of Letter C
In the conversion of aldoses to their ketoses, the _____ carbon loses its
stererochemistry.
C-3
C-2
C-4
C-5
C-1
The generic form of a hemiacetal is _________?
R-O-C-H
R-C-O-H
R-O-CH-OH R-C-C-OH
none
In Haworth projection of carbohydrates, the D and L prefix denotes the position of
the ______ group on carbon ______.
Carbonyl; 6
OH; 5
O-; 6
OH; 6
Carbonyl; 5
Below is the Haworth Projection of ______________.
α-L-Glucopyranose
α-D-Glucopyranose
β-D- Glucopyranose
β-L-Glucopyranose
D-Glucose
CH 460
Dr. Muccio
Spring 2014
Worksheet 4
Here, you have to know what the difference between ‘a’ and ‘b’ is: ‘a’ means the
C-1 OH is pointing down. ‘b’ points up.
Galactose forms a _______ ring structure where as fructose forms a ___________.
pyranose; furanose
__________ inverts the position of the anomeric carbon. The ring structure of
carbohydrates is ______ stable than the open chain form.
a. Epimerization; more
b. Mutarotation; more
c. Epimerization; less
d. Mutarotation; less
The ________ position on the anomeric carbon is the more stable.
a. L
b. D c. β d. α
Groups on the anomeric carbon are denoted by α and β, not D and L.
The ______anomer of the ______ form of ribose is the more stable. It occurs in a ______:1
ratio.
a. β; pyranose; 3
b. β; furanose; 4
c. α; pyranose; 3
d. α; furanose; 4
Can you identify the reducing and non-reducing end of the disaccharide below? Put
a star on the acetal carbon and a triangle around the hemiacetal carbon. Name the
sugar below.
Circled is reducing end. Acetal functional group is RO-CH-OR; hemiacetal is
RO-CH-OH. This is α-Glc (14)Glc or Maltose.
Which of the following disaccharides does not have a reducing end?
a. Lactose
b. Glucose
c. Cellobiose
d. Sucrose e. Amylopectin
Sucrose is the only disaccharide where both the anomeric carbons are tied up
in the glycosidic bond. Glucose is a monosaccharide and amylopectin is a
polysaccharide. Lactose and cellobiose have free anomeric carbons.
CH 460
Dr. Muccio
Spring 2014
Worksheet 4
Match the di/polysaccharides to their descriptions on the left. Some will have
multiple matches.
β-Glc (14)Glc ___AK______
α-Glc (12)-β-Fru ___BF____
α-Glc (14)Glc _____D_____
β-Fru (21)-α-Glc ____JB______
β-Gal (14)Glc ______H____
Amylopectin __GCN_____
Cellulose____IL____
Amylose ___EM_______
A. Cellobiose
B. Sucrose
C. Branched homoglycan of Glc
D. Maltose
E. Linear homoglycan of Glc
F. Has no reducing ends
G. Has α(1,6) branches
H. Lactose
I. Linear polymer of Glc with β(1,4)
glycosidic bonds
J. 100% sweet
K. Humans cannot digest – not
nutritional
L. hydrolyzed by Cellulases that break
β(1,4) bonds
M. Makes up a minority of plant
starch
N. Makes up a majority of plant starch