ZOOHCC - 501: Molecular Biology (Theory)
Unit 4: Translation
Protein synthesis in prokaryotes takes place in two main steps: transcription and translation.
Transcription:
The process begins when the enzyme RNA polymerase binds to the promoter region of a DNA molecule. The DNA double helix is unwound and RNA polymerase synthesizes a single-stranded mRNA molecule using one of the DNA strands as a template. As the RNA polymerase moves along the DNA template, the mRNA molecule lengthens and when the termination signal is reached, the RNA polymerase dissociates from the DNA template. The mRNA molecules then exit the nucleus and translocate into the cytoplasm. translation:
Ribosomes bind to mRNA molecules, and ribosomes read codons on the mRNA in order. Ribosomes recruit the appropriate tRNA molecule with the specific amino acid indicated by the codon. Amino acids are added to the growing polypeptide chain and the ribosome moves to the next codon. This process continues until the ribosome reaches the stop codon, at which point the newly synthesized polypeptide is released. In prokaryotes, transcription and translation can occur simultaneously because there is no nuclear envelope separating the two processes. Therefore, when an mRNA molecule is synthesized, it is immediately translated into a polypeptide chain by ribosomes.
Protein involvement
Proteins play an important role in the process of protein synthesis in prokaryotes. Here are some examples.
RNA polymerase: RNA polymerase is the protein enzyme involved in the transcription of DNA into RNA. It binds to the promoter regions of DNA molecules and catalyzes the formation of complementary strands of RNA.
Ribosome: Ribosome is a large molecular complex of RNA and protein. They are responsible for translating mRNA into polypeptide chains. Ribosomes have three distinct sites, the A site, the P site, and the E site, where tRNA molecules carrying specific amino acids bind and are used to assemble growing polypeptide chains.
Transfer RNA (tRNA): tRNA molecules are small RNA molecules involved in the translation of mRNA into polypeptide chains. Each tRNA molecule carries a specific amino acid that is added to the growing polypeptide chain. The tRNA molecule also has a sequence of three nucleotides called anticodons that are complementary to the codons on the mRNA.
Initiation Factors: Initiation factors are proteins involved in the initiation of translation. They help bring the ribosome and mRNA together and also help place the first tRNA molecule in the correct position in the mRNA.
Release Factors: Release factors are proteins involved in the termination of translation. They recognize stop codons in mRNAs and release newly synthesized polypeptide chains from ribosomes.
Briefly Explanation
The process of protein synthesis in prokaryotes is a complex molecular process involving multiple steps including transcription and translation. This is the process of using the genetic information encoded in DNA to synthesize proteins, which are essential molecules that perform various functions within the cell.
Transcription:
The first step in protein synthesis is transcription. This is the process by which genetic information encoded in DNA is copied into single-stranded RNA molecules known as messenger RNA (mRNA). Transcription takes place in the nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells. In prokaryotes, transcription is initiated when the enzyme RNA polymerase binds to the promoter region of a DNA molecule. The DNA double helix is unwound and RNA polymerase synthesizes a complementary strand of RNA using one of the DNA strands as a template. RNA polymerase adds nucleotides to the growing mRNA molecule until it reaches a termination signal. At this point, RNA polymerase dissociates from the DNA template. Newly synthesized mRNA molecules exit the nucleus and travel to the cytoplasm.
translation:
The second step in protein synthesis is translation. This is the process of using the genetic information encoded in mRNA to synthesize proteins. Translation takes place in the cytoplasm of both eukaryotic and prokaryotic cells.
In prokaryotes, translation may begin before transcription is complete. A large molecular complex of RNA and protein, the ribosome binds to the mRNA molecule and sequentially reads the codons on the mRNA. Ribosomes have three distinct sites, the A site, the P site, and the E site, where tRNA molecules carrying specific amino acids bind and are used to assemble growing polypeptide chains. Each tRNA molecule carries a specific amino acid that is added to the growing polypeptide chain. The tRNA molecule also has a sequence of three nucleotides called anticodons that are complementary to the codons on the mRNA. The ribosome moves to the next codon and adds the appropriate amino acids until it reaches the stop codon. Upon reaching the stop codon, the newly synthesized polypeptide is released from the ribosome.
Regulations:
The process of protein synthesis in prokaryotes is regulated at various levels. Transcription is regulated by the binding of regulatory proteins called transcription factors to specific DNA sequences known as enhancers and silencers. Transcription factors can either promote or repress gene transcription. Translation is regulated by several mechanisms, including the binding of regulatory proteins known as initiation factors to the mRNA molecule, which aid in the binding of the ribosome to the mRNA. Another regulatory mechanism is modification of the mRNA molecule itself. B. Removal of introns by splicing. Coding sequences can change and affect mRNA translation. Diploma:
The process of protein synthesis in prokaryotes is a complex molecular process involving multiple steps and regulatory mechanisms. It is essential for the function and survival of cells and organisms. Understanding the process of protein synthesis in prokaryotes is important for many branches of biology, including genetics, molecular biology, and biotechnology.
