Chapter 12, Problem 1RE

RECALL Prepare a flow chart showing the stages of protein synthesis.

Interpretation Introduction

Interpretation:

A flow chart representing various stages of protein biosynthesis is to be prepared.

Concept introduction:

Proteins are large macromolecules, which consist of long sequences of amino acid residues. They are involved in a number of different biochemical processes in an organism.

They mostly differ in their structure and activity due to the arrangement of amino acid residues that is governed by their gene makeup.

Answer to Problem 1RE

Solution:

Explanation of Solution

Biosynthesis of protein is a complicated process that requires messenger and transfer RNA (mRNA and tRNA), ribosomes, and various protein factors. Ribosomes are the primary location for the biosynthesis of protein, to which the mRNA and tRNA are attached. The mRNA and tRNA are crucial for the correct arrangement of amino acids in the elongating chain.

The amino acid must be activated prior to being incorporated in the protein chain. The activation of amino acids requires tRNA and aminoacyl-tRNA synthetases (a group of specific enzymes). The amino acid residues get attached covalently to the tRNA forming aminoacyl-tRNA. The actual synthesis of polypeptide sequences takes place in three steps (chain initiation, chain elongation, and chain termination).

In the chain initiation step, the primary aminoacyl-tRNA gets attached to mRNA at a point that codes the initiation of polypeptide biosynthesis. The mRNA is attached with the ribosome, forming a complex. The subsequent aminoacyl-tRNA then makes a complex with the complex of ribosome and mRNA. The binding position for the subsequent aminoacyl-tRNA is adjacent to the primary aminoacyl-tRNA. Now, in the chain elongation step, formation of a peptide bond takes place between the amino acids. This process recurs until the polypeptide chain is accomplished. At last, in the chain termination step, the newly synthesized protein is released from the ribosomes.

Conclusion

The protein molecules are long chains of amino acids, the information for which is stored in the genetic code.