SURVEY OF BIOCHEMISTRY
Carbohydrates
1
What are Carbohydrates?
• Generic Formula of Simple Carbs
(CH2O)n
• Sugars formed from CO2 and H2O
• Roles
– Energy in diet
– Mediating intercellular communication
– Structural support (e.g. cell walls)
2
Classification
• Monosaccharides
– Aldoses
– Ketoses
• Polysaccharides (Glycans, Glycosides)
• Glycoproteins: sugars bound to proteins
– N-linked Oligosaccharides
– O-Linked Oligosaccharides
3
Aldoses & Ketoses
Sugars made from aldehydes form
aldoses
Sugars made from ketones form
ketoses
4
Important Aldoses To Study
6-C sugars
5-C
sugar
All begin with CHO group
5
Important Aldoses To Study
6-C sugars
5-C
sugar
All end with
group
6
Important Aldoses To Study
6-C sugars
5-C
sugar
Most names end with -ose suffix
7
Important Ketoses To Study
3-C
sugar
5-C
sugar
6-C
sugar
Most names all end with -ulose suffix
8
Important Ketoses To Study
3-C
sugar
Ketoses begin with
5-C
sugar
6-C
sugar
group
9
Important Ketoses To Study
3-C
sugar
Most ketoses end with
5-C
sugar
6-C
sugar
group
10
Important Ketoses To Study
3-C
sugar
5-C
sugar
6-C
sugar
Several ketoses end with -ulose suffix
11
Structures of Monosaccharides
• Isomers and Epimers
• Enantiomers
• Anomeric Carbons
• Ways to Draw Monosaccharides
– Fischer Projection
– Haworth Projection
– Chair form
Preferred
12
Isomers
• Isomers are different compounds that have
the same chemical formula
C6H12O6
13
Epimers
Epimers are sugars that differ only by the
configuration around one carbon atom.
Only
difference
14
Enantiomers
See
Section
4-2
for help
Know this
structure
Most sugars are found in the D-stereoisomer.
D-Glyceraldehyde is the most simple aldose.
15
Cyclization of Monosaccharides
Anomeric Carbons
Anomeric
Carbon
16
Cyclization of Monosaccharides
Anomeric Carbons
Anomeric
Carbon
Conformations


Position of -OH Group on Anomeric C
Down
Up
17
Ways to Draw Monosaccharides
• Fischer Projection - linear
• Haworth Projection - cyclic
• Chair - cyclic



18
Cyclization of Monosaccharides
Up
Down
19
Cyclization of Monosaccharides
Up
Down
20
Polysaccharides
• Disaccharides: 2 sugars
– Lactose: Glucose + Galactose
– Sucrose: Glucose + Fructose
– Maltose: Glucose + Glucose
• Oligosaccharides: 3-12 sugars
• Polysaccharides: 13+ sugars
– Glycogen: homopolysaccharide of glucose
– Glycosaminoglycans: heteropolysaccharides
21
Polysaccharides
Monosaccharides can be linked to form oligosaccharides,
and ultimately polysaccharides via glycosidic bonds.
SUCROSE
Glycosidic Bond
22
Polysaccharides
Monosaccharides can be linked to form oligosaccharides,
and ultimately polysaccharides via glycosidic bonds.
LACTOSE
Glycosidic Bond
23
Glycosidic Bonds in RNA
24
Starch in Plants
25
Starch in Plants
26
Glycoproteins: N-Linked
27
Glycoproteins: O-Linked
28
PRS
• When comparing two enzymes, the
optimal catalytic activity can be
determined by_______.
1.
2.
3.
4.
The
The
The
The
smallest Km
largest KM
smallest Vmax
smallest kcat/KM
29
PRS
• Which class of enzyme catalyzes
group elimination to form double
bonds?
1.
2.
3.
4.
Transferases
Isomerases
Lyases
Ligases
30
PRS
• Which of the following proteins is
involved in muscle contraction?
1.
2.
3.
4.
Trypsin
Troponin
Chymotrypsin
Hemoglobin
31
PRS
• Which of the following is a ketose?
1.
2.
3.
4.
Glucose
Fructose
Ribose
Galactose
32