Saturday, February 12, 2011

Macromolecule 1: Carbohydrates

Carbohydrates are one of the four major groups of macromolecules which are essential to life as we know it. Composed primarily of carbon, hydrogen and oxygen in a fixed 1-2-1 ratio, these molecular compounds are produced and consumed by living organisms in order to attain energy. In addition, they are also used as building materials and for means of identification. Their importance is therefore undeniable.

Sugars are the subunit of carbohydrates. They can be categorized based on the number of carbon atoms present within their structure: for example, a sugar with 6-carbons would be called a "hexose". However, there are also different types of hexose sugars which are isomers of each other. Two examples would include glucose and galactose. These are examples of simple sugars are called monosaccharides and can be identified by the carbonyl group they possess.

These simple sugars can be assembled (through condensation reactions) or disassembled (through hydrolysis). The covalent bonds that hold these monomer units together are called glycosidic linkages. When linked together, two monosaccharides can form disaccharides. Likewise, many monomer units of this kind form polysaccharides.

For example:

Glucose + Glucose = Maltose
Glucose + Fructose = Sucrose
Glucose + Galactose = Lactose

It is also important to consider the position of the hydroxyl group in these polymer chains. A chain of alpha glucoses form starch (a carbohydrate that can be digested by humans), whereas a chain of beta glucoses for cellulose (a carbohydrate found in plants that cannot digested by humans).

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