The Two Processes Of Protein Synthesis Are – Protein biosynthesis starting from transcription and post-transcriptional modifications in the nucleus. The mature mRNA is exported to the cytoplasm, where it is translated. The polypeptide chain is assembled and undergoes post-translational modification.

Protein biosynthesis (or protein synthesis) is a fundamental biological process that occurs inside cells and balances the loss of cellular proteins (through degradation or export) by the production of new proteins. Proteins perform a number of key functions as zomes, structural proteins or hormones. Protein synthesis is a very similar process in both prokaryotes and eukaryotes, but there are some distinct differences.

The Two Processes Of Protein Synthesis Are

Protein synthesis can be broadly divided into two phases – transcription and translation. During transcription, a protein-coding section of DNA, called ge, is converted into a messenger molecule called messenger RNA (mRNA). This conversion is carried out by enzymes, known as RNA polymerases, in the cell’s nucleus.

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In eukaryotes, this mRNA is initially produced in a premature form (pre-mRNA), which undergoes post-transcriptional modifications to produce mature mRNA. Mature mRNA is exported from the cell nucleus through nuclear pores to the cell cytoplasm, where translation occurs. During translation, mRNA is read by ribosomes, which use the nucleotide sequence of the mRNA to determine the amino acid sequence. Ribosomes catalyze the formation of covalent peptide bonds between encoded amino acids, forming a polypeptide chain.

After translation, the polypeptide chain must assemble to form a functional protein; for example, to function as a zyme, the polypeptide chain must fold correctly to produce a functional active site. To assume a functional three-dimensional (3D) shape, a polypeptide chain must first form a series of smaller structures called secondary structures. The polypeptide chain in these secondary structures folds to form an overall 3D tertiary structure. Once properly assembled, the protein can undergo further maturation through various post-translational modifications. Post-translational modifications can change a protein’s ability to function where it is located in the cell (e.g., in the cytoplasm or nucleus) and the protein’s ability to interact with other proteins.

Protein biosynthesis plays a key role in disease because changes and errors in this process, resulting from DNA mutations or protein misfolding, are often the primary cause of disease. DNA mutations change the next mRNA sequence, which changes the sequence of amino acids encoded in the mRNA. Mutations can shorten the polypeptide chain by creating a stop sequence that causes translation to terminate prematurely. Alternatively, a mutation in the mRNA sequence changes the specific amino acid encoded at that position in the polypeptide chain. This change in amino acids can affect the protein’s ability to function properly or fold correctly.

Misfolded proteins are often associated with disease because misfolded proteins tend to stick together, forming clumps of dse protein. These lumps are associated with a number of diseases, often neurological, including Alzheimer’s disease and Parkinson’s disease.

Chapter 10: Transcription And Rna Processing

Transcription occurs in the nucleus using DNA as a template to produce mRNA. In eukaryotes, this mRNA molecule is known as pre-mRNA because it undergoes post-transcriptional modifications in the nucleus to form the mature mRNA molecule. However, in prokaryotes, post-transcriptional modifications are not required, so the mature mRNA molecule is immediately produced by transcription.

Illustrates the structure of a nucleotide with 5 carbon atoms labeled, showing the 5′ nature of the phosphate group and the 3′ nature of the hydroxyl group needed to form the connecting phosphodiester bonds

Illustrates the intrinsic directionality of a DNA molecule with the coding strand running from 5′ to 3′ and the complementary template strand running from 3′ to 5′

Initially, the DNA molecule is acted upon by a enzyme called helicase. DNA has an antiparallel double helix structure composed of two complementary polynucleotide strands connected by hydrogen bonds between base pairs. Helicase breaks hydrogel bonds, causing the age-specific region of DNA to relax, separating the two DNA strands and exposing a series of bases. Even though DNA is a double-stranded molecule, only one of the strands acts as a template for the synthesis of pre-mRNA – this strand is called the template strand. The second strand of DNA (which complements the template strand) is called the coding strand.

Solved Activity #8 Translation 1. Objective: To Illustrate

Both DNA and RNA have intrinsic directionality, which means there are two different molecules. This property of directionality is due to the asymmetric base nucleotide subunits, with a phosphate group on one side of the ptose sugar and a base on the other. The five carbon atoms in ptose sugar are numbered from 1′ (where ‘is a prime number) to 5′. Therefore, phosphodiester bonds connecting nucleotides are formed by combining the hydroxyl group on the 3′ carbon of one nucleotide with the phosphate group on the 5′ carbon of another nucleotide. Thus, the coding DNA strand runs in the 5′ to 3′ direction, and the complementary, template DNA strand runs in the opposite direction from 3′ to 5’.

The zyme RNA polymerase binds to the exposed template strand and reads from ge in the 3′ to 5′ direction. At the same time, RNA polymerase synthesizes a single strand of pre-mRNA in the 5′-3′ direction, catalyzing the formation of phosphodiester bonds between activated nucleotides (free in the nucleus), which are capable of complete base pairing with the template strand. Behind the moving RNA polymerase, the two DNA strands reconnect, so only 12 DNA base pairs are exposed at a time.

RNA polymerase builds a pre-mRNA molecule at a rate of 20 nucleotides per second, allowing thousands of pre-mRNA molecules of the same size to be produced in an hour. Despite its rapid rate of synthesis, the RNA polymerase enzyme contains its own proofreading mechanism. Proofreading mechanisms allow RNA polymerase to remove incorrect nucleotides (that are not complementary to the template DNA strand) from the growing pre-mRNA molecule through an excision reaction.

When RNA polymerases reach a specific DNA sequence that completes transcription, the RNA polymerase detaches and pre-mRNA synthesis is completed.

Mechanisms And Regulation Of Protein Synthesis In Mitochondria

The synthesized pre-mRNA molecule is complementary to the template DNA strand and has the same nucleotide sequence as the coding DNA strand. However, there is one fundamental difference in the nucleotide composition of DNA and mRNA molecules. DNA is made up of bases – guanine, cytosine, adine and thymine (G, C, A and T) – RNA is also made up of four bases – guanine, cytosine, adine and uracil. In RNA molecules, the basic DNA thymine is replaced by uracil, which can form base pairs with adine. Therefore, in the pre-mRNA molecule, all complementary bases, which would be thymine in the coding DNA strand, are replaced by uracil.

It presents the process of post-transcriptional modification of pre-mRNA through capping, polyadylation and splicing to produce a mature mRNA molecule ready for export from the nucleus.

The 5′ cap is added to the 5’d end of the pre-mRNA molecule and consists of a guanine nucleotide modified by methylation. The purpose of the 5′ cap is to prevent the degradation of mature mRNA molecules prior to translation, the cap also helps bind the ribosome to the mRNA to initiate translation

In contrast, the 3′ Poly(A) tail is added to the 3’d of the mRNA molecule and consists of 100-200 adine bases.

Question Video: Identifying How A Polypeptide Is Formed

These distinct mRNA modifications enable the cell to detect that the full mRNA message is intact if both the 5′ cap and 3′ tail are present.

This modified pre-mRNA molecule undergoes the RNA splicing process. Ges consist of a series of introns and exons, introns are nucleotide sequences that do not code for a protein, while exons are nucleotide sequences that directly encode a protein. Introns and exons are stable in both the primary DNA sequence and the pre-mRNA molecule, so splicing must occur to produce a mature protein-coding mRNA molecule.

During splicing, spacer introns are removed from the pre-mRNA molecule by a multi-protein complex known as the spliceosome (consisting of over 150 proteins and RNA).

This mature mRNA molecule is exported to the cytoplasm through the nuclear pores in the nuclear cavity.

Sketch The General Process Of Protein Synthesis Below.

Illustrates the translation process by showing the tRNA codon-anticodon pairing cycle and the incorporation of amino acids into the growing polypeptide chain by the ribosome.

The ribosome on the mRNA strand arrives with the tRNA, performing codon-anti-codon pairing, delivering its amino acid to the growing polypeptide chain, and leaving. Demonstrates the functioning of the ribosome as a biological machine operating at the nanoscale to perform translation. The ribosome moves along the mature mRNA molecule, turning on the tRNA and forming a polypeptide chain.

During translation, ribosomes synthesize polypeptide chains from mRNA template molecules. In eukaryotes, translation occurs in the cytoplasm of the cell, where ribosomes float freely or are attached to the endoplasmic reticulum. In prokaryotes, which do not have a nucleus, both transcription and translation processes occur in the cytoplasm.

Ribosomes are complex molecular machines, made of a mixture of protein and ribosomal RNA, arranged in two subunits (large and small subunit) that surround an mRNA molecule. The ribosome reads the mRNA molecule in the 5′-3′ direction and uses it as a template to determine the order

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