‘Some biological molecules in organisms are small and simple containing only one or a few functional groups, others are large, complex assemblies called macromolecules’ .
The term macromolecule is convenient because the bulk properties of a macromolecule differ from those of smaller molecules. These large chemical compounds have a high molecular weight consisting of a number of structural units linked together by covalent bonds, giving them a variety of structures and functions in the body. Macromolecules (also known as supermolecules) are commonly grouped into four major categories: proteins, nucleic acids, lipids and carbohydrates. These are mainly composed of polymers, long molecules made up of a large number of small, similar molecules, or monomers.
Proteins are polymers of amino acids. Long amino acid chains are folded into complex shapes, the shape of each determining the function of the protein. They are complex organic compounds, essential to the functioning as well as the structure of all organic cells. Proteins range in size from a few amino acids to thousands, having a wide range of important roles covering structural support, cell protection, catalysis, transport, defense, regulation and movement.
The specific amino acid sequence of a protein forms its primary structure. The folding of the amino acid chain by hydrogen bonding into coils and pleats forms a protein's secondary structure.
The nucleic acids occur chiefly in combination with proteins. These informational macromolecules are complex chemical compounds found in all living cells. They are long polymers of linked nucleotides consisting of a five-carbon sugar, a phosphate, and a nitrogen-containing base, creating very long, very rigid rods, such that they would be shattered by shear forces at the tip of a pipette if pipetted.
One form of nucleic acid, deoxyribonucleic acid (or DNA), encodes the...