Biomolecules:
Carbohydrates

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In this module:

Introduction
Definition
Linear and Cyclic Forms
Anomers
Disaccharides
Polysaccharides
Variations
Other Functions

Glucose: Linear and Cyclic Forms

One of the most important carbohydrates in the body is glucose (C6H12O6). Glucose is called a monosaccharide because it forms one simple building block of more complicated carbohydrates. One structure of glucose is shown below.

Click on the step numbers below to see some important things about glucose's structure. Click on the mouse at left to clear the text and reset the image.

The functional groups are the aldehyde and hydroxyl groups.

1.

Because of these polar functional groups, glucose (and other monosaccharides) are highly soluble in water (1.5 g/mL at 25 ºC).

2.

Linear glucose has four chiral carbons (pointed to by the red arrows).

3.

The linear form of glucose shown above makes up less than 3% of the glucose molecules in a water solution. The rest is one of two cyclic forms of glucose formed when the hydroxyl group on carbon 5 (C5) bonds to the aldehyde carbon 1 (C1), as shown below.

Where did all the carbons go? Why do some carbons have less than four bonds?

Linear and Cyclic Forms