Carbohydrates play four main functions:
1) They are the main source of energy for cells.
2) Carbohydrates store reserve energy.
3) Carbohydrates provide carbon skeletons to build new molecules.
4) Carbohydrates constitute structural materials for supporting and covering cells.
Monosaccharides
Monosaccharides are divided into aldoses (e.g., glucose) and ketoses (e.g., fructose).
Composition:
- Carbon chain
- One carbon atom carries the carbonyl group
- The other carbon atoms carry a hydroxyl group
C6H1206
Hexoses: six carbon atoms and all have the same shape.
The most widespread is glucose.
Pentoses: five carbon atoms (e.g., ribose and deoxyribose)
A sugar has six carbon atoms (hexose)
H,OH
НО
H
H
OH HO
OH
Marinasio
A The glycosidic bond
CH,OH
0 H
H
OH H
A OH
Glucose
H OH G
014
OH
OH H
OH
CH,OH,
OH,OH
HOH
T
H
Galactose
H
COH
T2
OH
ON H
Fructose
150
OHV
CH,OH
Formation
H of a glycosidic bond
H,OH
Н,О
OH A
Fructose
OH
H
OH
H₂OH
MONOSACCHARIDES FORM GLYCOSIDIC BONDS
A single glycosidic bond between two monosaccharides forms a DISACCHARIDE
Glucose + Fructose = Sucrose (disaccharide)
Glycosidic bond
CH,OH
-0 H
OH H
H OH
Glucose
O
CH,OHO
H
Sucrose
SCH,OH
H
B Sugars with five carbon atoms (pentoses)
OH
Fructose
OH
OH ZOH
Ribose
H
OCH₂OH
H/H
4C
H
H
H-C-OH
HO-C-H
H-C-OH
H-C-OH
CH₂OH
H,OH
D-Glucose
an aldo-hexose
HA
OH
Deoxyribose
H
H-C-OH
C=O
HO-C-H
H-C-OH
H-C-OH
CH₂OH
D-Fructose
a keto-hexose
Two or more monosaccharides linked through a glycosidic bond form oligosaccharides.
Summary
In conclusion, monosaccharides are simple sugars such as glucose and fructose, while disaccharides and polysaccharides are formed by bonding multiple monosaccharides. These carbohydrates serve various functions, including providing energy, storing reserves, and creating structural materials for cells. Glycosidic bonds are crucial in forming disaccharides and polysaccharides, contributing to their diverse roles in biological systems.
