Chemistry Reference
In-Depth Information
CH
2
OH
O
OH
O
OH
HO
OH
HO
OH
HO
OH
OH
Ribose
Glucose
FIGURE 5.1
Chemical structures of two monosaccharides: glucose and ribose.
O
OH
HO
HO
HO
OH
OH
O
OH
HO
OH
OH
CH
2
OH
O
HO
O
H
H
OH
OH
CH
2
OH
FIGURE 5.2
Alternative forms of the six-membered ring sugar.
5.3 FRUCTOSE AND GLUCOSE
Fructose is a simple sugar commonly found in fruits and vegetables. Glucose, also
known as grape or blood sugar, is present in all major carbohydrates, for example,
starch and table sugar. Although both are a good source of energy, excess of glucose
can be fatal to diabetic patients, and excess of fructose in the human body can lead
to health problems such as insulin resistance and liver disease
.
5.4 THE DISACCHARIDE SUCROSE
There are two types of sugars: reducing and nonreducing. Monosaccharides are
almost all reducing sugars, for example, glucose or lactose. Detection is achieved
with the use of Fehling's reagent. In the Fehling reaction, reducing sugars should
turn red and develop a red precipitate, which comes from the reduction of copper (II)
ions to copper (I) oxide.
Conversely, a good example of a nonreducing sugar is sucrose (Figure 5.4).
Sucrose is composed of glucose (left) and fructose (right), which are linked together
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