What are macromolecules and why are they important?

Published: 08th July 2010
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The term macromolecule by definition implies "large molecule". In the context of biochemistry, 'macromolecule' is used to describe nucleotides, proteins, carbohydrates, and lipids. For example, a protein may consist of 1000s of atoms and may weigh a 100,000 Daltons.

A polymer is a long molecule consisting of many similar or diverse building blocks (monomers) linked by covalent bonds.

What is the difference between dehydration and hydrolysis? A dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions. Two monomers can be brought together and covalently attached by the loss of a water molecule between them. This is a dehydration reaction, since water is lost.
Example of Dehydration Reaction: Conversion of alcohols to ethers

2 R-OH → R-O-R + H2O

A hydrolysis reaction is when an H2O molecule is added to oxygen to produce two Hydroxide groups, thus separating the bonds at the spot.
Hydrolysis is a chemical reaction during which one or more water molecules are split into hydrogen and two hydroxide ions which may go on to participate in further reactions. Hydrolysis is used to break down certain polymers. Hydrolysis can be considered as the reverse or opposite of condensation.

Polysaccharide molecules are hydrolyzed into monosaccharide molecules. In polysaccharides, monosaccharide molecules are linked together by a glycosidic bond. This bond can be cleaved by hydrolysis to yield monosaccharides.

How exactly do monomers combine to form polymers?
Two monomers 1 and 2 can both have hydrogen (H) and hydroxyl groups (OH) attached to them. When they come together with an appropriate catalyst, one monomer loses a hydrogen while the other loses a hydroxyl group. The hydrogen and hydroxyl groups combine to form water (H2O), and the remaining electrons form a covalent chemical bond between the monomers. The resulting compound is the basic subunit of copolymers 1 and 2. This reaction may occur over and over again until you get a long chain of copolymers 1 and 2.

An enzyme is a specialized molecule that can speed up chemical reactions, such as the reactions that bring monomers together to form polymers.

How is food absorbed by the body? Food is absorbed in the form of polymers. Polymers are broken down to monomers by hydrolysis. When water is added to a polymer, a hydrogen atom from water can attach to the end of one monomer. The remaining hydroxide ion can attach to the end of the adjacent monomer, slicing the polymer at that point.

For example, enzymes in the digestive tract of humans break down the polymers into monomers in this way. The monomers are appropriately sent to cells as nutrition. Once they reach the cell, they can be re-assembled into polymers to be used for diverse cellular needs.

Each human cell has 1000s of different kinds of macromolecules (1000s of proteins). While only 40-50 monomers are used, the number of polymers created from these numbers in the 1000s.

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