Lesson 6 : Carbohydrates - Classification- Structure, Function


Carbohydrates can be classified as simple (monosaccharides and disaccharides) or complex (oligosaccharides and polysaccharides).


  1. Monosaccharides are single sugars including:

    • Fructose
    • Glucose
    • Galactose

  2. Disaccharides (simple sugars) are two sugars linked through together including:

    • Sucrose (table sugar), composed of glucose and fructose
    • Lactose (milk sugar), composed of glucose and galactose
    • Maltose (malt sugar), composed of glucose and glucose

  3. Polysaccharides (complex carbohydrates) are many sugars linked together including:

    • Starch, composed of many glucose molecules
    • Glycogen (storage form of carbohydrate in the body), composed of many glucose molecules
    • Fiber (nonstarch polysaccharides), composed of many glucose molecules, which the human body cannot break down

  4. glycoconjugates - derivatives; attached to proteins, lipids, peptide chains

Two monosaccharides joined by covalent bond called a glycosidic linkage via a condensation reaction.

Bond is created between the C-1 of one sugar and the -OH of another carbon

Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group, the number of carbon atoms it contains

If the carbonyl group is an aldehyde, the monosaccharide is an aldose; if the carbonyl group is a ketone, the monosaccharide is a ketose. Monosaccharides with three carbon atoms are called trioses, those with four are called tetroses, five are called pentoses, six are hexoses, and so on. These two systems of classification are often combined. For example, glucose is an aldohexose (a six-carbon aldehyde), ribose is an aldopentose (a five-carbon aldehyde), and fructose is a ketohexose (a six-carbon ketone).

Last modified: Tuesday, 17 January 2012, 11:39 AM