Page 77 - The Manga Guide to Biochemistry

Saccharides and the “-ose” suffix

You’ve probably noticed that most of the saccharides we’ve discussed so far, like glucose and
galactose, end with the suffix “-ose.” There are standardized rules for naming saccharides,
so these names usually end with “-ose.”

For instance, glucose is the saccharide that’s the basis of energy production, and it’s the
sugar referred to when we talk about blood sugar. Common table sugar is technically called
sucrose. Milk contains a saccharide called milk sugar, which is known as lactose, and the
sugar contained in fruit is called fructose. It’s important to remember that there are several
kinds of saccharides in the natural world, and the structures of sucrose, lactose, glucose,
galactose, and fructose actually differ somewhat. Also, the starch found in rice, potatoes, and
other starchy foods is made from amylose and amylopectin.

In Chapter 3, we’ll examine the structures of these saccharides in detail.

Why do monosaccharides take a cyclic structure?

Why do monosaccharides take a cyclic structure more often than an open-chain ­structure?
The secret is in an OH that’s bonded to a carbon in the molecule.

Alcohol is a good example of this: All types of alcohol are represented in the form R-OH
(where R is the variable group). Alcohol can bind with an aldehyde group or a ketone group
to create a substance called hemiacetal. Since an OH of a monosaccharide also has this
property, the monosaccharide ends up reacting with an aldehyde group or a ketone group
within the molecule, and a cyclic structure is formed as the result.

H RO H
+ R´ C
R OH C
O
Alcohol R´ OH
Aldehyde
Hemiacetal

H O

1 Aldehyde

C 6 CH2OH

2 CH2OH

H C OH H 5C OH H H O H
H OH
3 4 H1
C H
HO C H C OH H
O OH
4 HO 32 HO
CC
H C OH Aldehyde

5

H C OH

6CH2OH H OH H OH

The OH in the fifth position of ...to form a cyclical
the monosaccharide reacts structure.
with the aldehyde...

Photosynthesis and Respiration 63