The process of protein synthesis is the most complicated biological activity. Basically it is governed by the genetic information carried in the genes (DNA) of the chromosomes.
Specific amino acids are linked in particular sequence or order to form a polypeptide chain of protein.
The various cell organelles and chemical compounds involved in the synthetic process are:
1. Deoxyribonucleic acid DNA
2. Three type of ribonucleic acids RNA
3. Amino acids
4. Enzymes and
The discussion above will clearly reveal that proteins are the representative of the master molecule of the cell DNA to carry out and regulate all the metabolic activities. Proteins are important in another way also.
They are important for the existence of DNA itself. A number enzyme (proteins) is necessary for the replication of DNA itself.
When proteins are of such fundamental biological importance, no wonder then the cell machinery to synthesize them (proteins) is not only complicated but precisely regulated.
Which molecule(s) present in the cell can regulate the synthesis of proteins? Obviously there cannot be another compound than DNA.
The structure and properties of the DNA molecule are eminently suited to exercise such a regulation over the synthesis of proteins.
Having conceded that DNA directly is involved in the regulation of protein synthesis we may now try to answer the two following questions – which aspect of protein structure is controlled by DNA?
And how and by what mechanism DNA regulates the assembly of amino acids to synthesize the proteins?
Proteins are extremely complicated biological macromolecules. There are different dimensions for its structural complexity and integrity.
These are the primary, secondary, tertiary and quaternary structures (for details – see later in protein synthesis). DNA molecule specifies only the primary structure, while other dimensions of protein structure like folding etc is controlled by proteins themselves.
The primary structure of proteins involves the following aspects – quality, quantity and sequence of amino acids and it is this that is regulated by DNA.
What is the mechanism adopted by DNA to regulate the synthesis of proteins? Obviously proteins cannot be synthesized in situ i.e. within the nucleus, because all the components needed for proteins-amino acids – ribosome’s etc is not present in the nucleus.
It is not possible also for the DNA itself to migrate to cytoplasm to synthesize the proteins. The only alternative is for DNA to send a messenger or representative which carries the message to specify the quality, quantity and the sequence of amino acids to be assembled to produce the protein.
This message is called the genetic code, because it specifies in genetic language the amino acids to be assembled.