Similarities and differences between prokaryotic and eukaryotic translational initiation complexes 5

In eukaryotic cells, the ribosomal small subunit 40s first and initiates the aminoacyl tRNA structure, while the prokaryotic ribosomal small subunit 30s first binds to mRNA.

There are more than a dozen initiation factors involved in eukaryotes, and there are only 3 prokaryotes, including iF1, iF2, and iF3 ribosomes with different subunit sedimentation rates.

Unlike initiating aminoacyl tRNAs, prokaryotes require formylation.

The mechanisms of small subunit and mRNA localization are different. The eukaryotes are the 5-terminal caps and 3-segment polya tails, and the pronucleus is the purine-rich SD sequence and the small nucleotide sequence downstream of it.

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The genes encoding proteins in eukaryotes are usually intermittent and discontinuous, because the introns and exons are transcribed together during transcription, so the messenger RNA produced by transcription must be processed, the intron transcription part is cut off, and the exon transcription part is spliced together to become a functionally mature messenger RNA. However, the genes of prokaryotes do not contain exons and introns, so the messenger RNA produced by transcription does not need to be sheared, spliced and other processing.

Furthermore, the transcription and translation of prokaryotic genes usually take place at the same time and place, i.e., translation begins before transcription is completed. For example, in the process of lactose catabolism in Escherichia coli, the transcription and translation of three structural genes are carried out in the cytoplasm at the same time. Eukaryotes have a nucleus and the nuclear membrane separates the nucleoplasm from the cytoplasm, therefore, transcription takes place in the nucleus and translation takes place in the cytoplasm.

It can be seen that the transcription and translation of eukaryotic genes are separated in time and space. The above-mentioned processes such as splicing, splicing, and transfer of eukaryotic genes after transcription all require the regulation of regulatory sequences, which are not found in prokaryotes.

Eukaryotes have untranslated introns in their genes, and prokaryotes have no introns and non-coding regions.

Select D. a. Organisms made up of prokaryotic cells are called prokaryotes, a correct.

B. Bacteria and cyanobacteria are both prokaryotes, B is correct.

c. Prokaryotes do not have a formed nucleus (no nuclear membrane, nucleolus and chromosomes), and there is a nucleus in the dust, c is correct.

d. Some prokaryotes can also carry out photosynthesis, such as cyanobacteria, d error.

Knowledge point analysis.

The structure of prokaryotic cells, or their genetic and variant characteristics, are the focus of the examination. It is important to remember that prokaryotic cells have only one organelle, ribosomes, and even though it can photosynthesize or aerobic respiration, it does not have chloroplasts or mitochondria.

It is also important to know that transcription and translation of prokaryotic cells can occur simultaneously and in the same place; Eukaryotic cells are transcribed first and then translated, in different places: transcription is in the nucleus and translation is in ribosomes.

a. Organisms composed of prokaryotic precursor cells are called prokaryotes, a correct;

b. Bacteria and cyanobacteria belong to the source of the prokaryotes, b is correct;

c. Prokaryotes do not have a formed nucleus (no nuclear membrane, nucleolus, and chromosomes), but they do have a nucleoid, c is correct;

d. Some prokaryotes can also carry out photosynthesis, such as cyanobacteria, dFalse, so hail locust selection: d

Semi-preserved replication, discontinuous synthesis, and the starting point and direction of replication all require DNA polymerase, helicase, etc.

Differences between prokaryotic and eukaryotic replication:

1. Eukaryotes are linear DNA, with multiple replication start sites, forming multiple replication forks, and the movement speed of DNA polymerase is slower than that of prokaryotes. Prokaryotes are generally circular DNA with a single replication start site.

2. Eukaryotary DNA replication only occurs in the S phase of the cell cycle, and replication is no longer carried out after the start of a replication, and multiple replication in prokaryotes is carried out at the same time.

3. Eukaryotary replicon sizes are different and not synchronized.

4. Prokaryotes have replication start sites composed of 9-mer and 13-mer repeating sequences, while eukaryotes have no fixed replication start sites.

Translation process.

Activation of amino acids.

The prokaryotic starting amino acid is formylmethionine, and eukaryotic begins with the generation of methionyl-tRNAi (MET superscaler).

The beginning of translation.

The starting tRNA of the pronucleus is fmet-tRNA (fmet superunit), and the 30S small subunit first binds to the mRNA template, then to the fmet-tRNA (fmet superunit), and finally to the 50S large subunit. The initiating tRNA in eukaryotic is.

Met-tRNA (Met superlabel), the 40S small subunit first binds to Met-tRNA (Met Upper Label), then to the template mRNA, and finally to the 60S large subunit to generate the initiation complex.

Extension of peptide chains.

There is no difference. Termination of the peptide chain.

Pronucleus contains three release factors, RF1, RF2, RF3. The eukaryotes only have ERF1 and ERF3.

Processing of protein precursors.

Folding of proteins.

Inhibition of protein synthesis.

This three-step process is overly complex and varies from species to species.

Activation of amino acids during translation: the prokaryotic starting amino acid is formylmethionine, and eukaryotic begins with the generation of methionyl-trnai (MET superlabel). The beginning of translation.

The starting tRNA of the pronucleus is the fmet-tRNA (fmet superunit) reading, and the 30s small subunit first binds to the mRNA template, then to the fmet-tRNA (fmet superstar), and finally to the 50s large subunit. The initiation tRNA in eukaryotes is met-tRNA (Met superlabel), and the 40s small subunit first binds to Met-tRNA (Met superlabel), then to the template mRNA, and finally to the 60S large subunit to form the initiation complex. Extension of peptide chains.

There is no distinction between the termination of the peptide chain: the pronucleus contains three release factors: RF1, RF2, RF3. The eukaryotes only have ERF1 and ERF3.

The processing of protein precursors, the folding of proteins, and the inhibition of the synthesis of high white matter are too complex and vary from species to species.

Answer]: The prokaryotic remainder biological translation initiation complex is composed of nucleoprotein size subunits, mRNA, and Woolling initiation aminoacyl-tRNA. The origin of the original cavity destroys the nucleozoan, and the aminoacyl-tRNA is formylmethionyl-tRNA.

The condensation of amino acids on ribosomes into polypeptide chains is achieved through ribosomal cycling. This cycle can be divided into three main processes: the initiation of peptide chain synthesis, the elongation of peptide chains, and the termination of peptide chain synthesis. The process of protein synthesis in prokaryotic cells takes cells as an example.

Initiation of peptide chain synthesis.

1.The ribosome 30s subunit of the Trimmer Complex is attached to the initiation signal site of mRNA, and this binding reaction is mediated by initiation factor 3 (IF3) with the participation of Mg2+. Therefore, the IF3-30S subunit-mRNA ternary complex was formed.

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Formation of the pre-initiation complex (30s pre-initiation complex) Under the action of initiation factor 2 (IF2), formylmethionine-initiation tRNA (fmet-tRNA met) binds to the initiation codon (AUG or GUG) in the mRNA molecule, that is, the codon reacts with the anticodon. At the same time, IF3 was detached from the ternary complex to form a 30 s pre-start complex, i.e., the IF2-30S subunit-mRNA-FMET-TRNAMEF complex. This step also requires FGTP and MG2+ participation.

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The initiation complex (70s initiation complex) is formed. The 50S subunit binds to the pre-30S initiation complex described above, while IF2 sheds off to form the 70S initiation complex, the 30S subunit-mRNA-50S subunit-fmer-tRNA Met complex. At this time, the fmet-trna met occupies the peptidyl site of the 50s subunit (p-site or donor), while the aminoacyl site (abbreviated as the A site or acceptor site) of the 50s subunit is temporarily vacant.

The initiation of protein synthesis in prokaryotic cells is the activation of amino-vussinyl orange (FMET-TRNAMET formation).

Summary. Prokaryotic translation is a biological process in which mRNA plays a key role in the synthesis of amino acids, which can translate a series of messenger RNAs into a series of amino acids that can be used to prepare proteins. This process can be broken down into four steps:

Binding, primer selection, primer polymerization and dissociation. 1.Combine:

In the prokaryotic translation reaction, the nucleic acid molecule mRNA binds to the complex macromolecule to form the mRNA-transcription factor complex (mRNA-TF). This complex is called ribosome and is made up of a large amount of RNA and proteins. 2.

Primer selection: Every three nucleotides encode an amino acid, called a "codon", and the start codon is determined by identifying and binding the start codon. 3.

Primer polymerization: After each identified codon, the ability to add amino acids to the alpha peptide chain joins adjacent codons to form a peptide chain, resulting in the multipolymerization of amino acids and the creation of new proteins. 4.

Dissociation: After the peptide chain has completed translation, the ribosome will break down into its original RNA and protein, so that the protein will be released to complete the prokaryotic translation process.

Prokaryotic translation is a biological process in which mRNA plays a key role in the synthesis of amino acids, which translates a series of messenger RNAs into a series of amino acids that can be used to prepare proteins. This process can be broken down into four steps: binding, primer selection, primer polymerization, and dissociation.

1.Binding: In the prokaryotic translation reaction, the nucleic acid molecule mRNA binds to the complex macromolecule to form the mRNA-transcription factor complex (mRNA-TF).

This complex is called ribosome and is made up of a large amount of RNA and proteins. 2.Primer selection:

Every three nucleotides encode an amino acid, called a "codon", and the start codon is determined by the step of identifying and binding the start codon. 3.Primer polymerization:

After each recognized codon, the ability to add amino acids to the alpha peptide chain joins the adjacent codons to form a peptide chain, which enables the multipolymerization of amino acids and the creation of new proteins. 4.Dissociation:

After the peptide chain is translated, the ribosome breaks down into its original RNA and protein, which is released to complete the prokaryotic translation process.

Kiss as above.