Elongation and Termination in Protein Synthesis

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Questions and Answers

During translocation, what is the energy source that allows tRNA to shift from the A site to the P site?

ATP

AMP

ADP

GTP (correct)

What is the role of a release factor during translation?

Reading the genetic code on the mRNA

Adding an amino acid to the growing polypeptide chain

Initiating the translation process

Terminating the translation process (correct)

What type of proteins do free ribosomes primarily synthesize?

Proteins that are embedded in the cell membrane

Proteins that are secreted from the cell

Proteins of the endomembrane system

Proteins that function in the cytosol (correct)

What is the result of the polypeptide chain shifting from the P site to the A site during translation?

The tRNA in the P site is released Signup and view all the answers

Bound ribosomes synthesize proteins that are primarily:

Part of the endomembrane system Signup and view all the answers

What is the purpose of translocation during translation?

To shift the mRNA by one codon along the ribosome Signup and view all the answers

What is the result of the release factor binding to the A site during translation?

The release of the polypeptide chain from the ribosome Signup and view all the answers

What is the role of GTP during translocation?

To provide energy for the translocation process Signup and view all the answers

What is the purpose of the E site during translation?

To exit the tRNA from the ribosome Signup and view all the answers

What occurs when a stop codon reaches the A site during translation?

The translation process is terminated Signup and view all the answers

What is the function of RNA polymerase in transcription?

To catalyze the synthesis of RNA Signup and view all the answers

What is the role of the 5' cap in RNA modification?

All of the above Signup and view all the answers

What is the function of RNA splicing?

To remove introns and join exons Signup and view all the answers

What is the structure of tRNA?

An L-shaped molecule with a 5' and 3' end Signup and view all the answers

What is the function of ribosomes in translation?

To translate mRNA into protein Signup and view all the answers

What is the genetic code?

A triplet code that translates into amino acids Signup and view all the answers

What is the result of alternative splicing?

Different proteins are formed from the same gene Signup and view all the answers

What is the function of ribozymes?

To catalyze the splicing of RNA Signup and view all the answers

What is the role of the TATA box in transcription?

To bind RNA polymerase Signup and view all the answers

What is the function of RNA polymerase III?

To synthesize snRNA and miRNA Signup and view all the answers

What is the result of the addition of a water molecule during translation?

Release of the polypeptide Signup and view all the answers

During translation, what is the purpose of the energy from GTP?

To translocate the mRNA along the ribosome Signup and view all the answers

What is the primary function of free ribosomes?

To synthesize proteins that function in the cytosol Signup and view all the answers

What occurs during elongation, when a tRNA is in the A site and the polypeptide chain shifts from the P site?

The tRNA in the A site shifts to the P site Signup and view all the answers

What is the role of the A site during termination?

It binds to the release factor Signup and view all the answers

What is the purpose of translocation during translation?

To shift the mRNA along the ribosome Signup and view all the answers

What is the primary function of elongation factors during translation?

To facilitate the formation of peptide bonds Signup and view all the answers

What is the result of peptide bond formation during translation?

A new amino acid is added to the C-terminus of the growing chain Signup and view all the answers

What is the role of initiation factors during translation?

To bring the small subunit to the mRNA and initiate translation Signup and view all the answers

What is the purpose of translocation during translation?

To shift the tRNA from the A site to the P site Signup and view all the answers

What occurs during the codon recognition step of elongation?

The tRNA is positioned on the A site of the ribosome Signup and view all the answers

What is the result of the polypeptide chain being shifted from the A site to the P site during translation?

The next amino acid is added to the growing chain Signup and view all the answers

What is the role of poly-A tail in RNA modification?

To increase the stability of the mRNA Signup and view all the answers

What is the function of the 5' cap in RNA modification?

To protect the mRNA from hydrolytic enzymes Signup and view all the answers

What is the result of RNA modification during transcription?

The mRNA is protected from hydrolytic enzymes and facilitated for export Signup and view all the answers

What is the function of RNA splicing during post-transcriptional modification?

To remove introns and join exons Signup and view all the answers

During what stage of translation does the polypeptide chain undergo post-translational modifications?

After translation is complete Signup and view all the answers

Which of the following factors is NOT involved in the formation of peptide bonds during translation?

Initiation factors Signup and view all the answers

What is the primary function of elongation factors during translation?

To facilitate the translocation of tRNA during elongation Signup and view all the answers

During translocation, which site does the tRNA in the A site move to?

P site Signup and view all the answers

What is the energy source that allows the tRNA to shift from the A site to the P site during translocation?

GTP Signup and view all the answers

What is the role of initiation factors during translation?

To facilitate the binding of mRNA to the ribosome Signup and view all the answers

What is the primary function of poly-A tail in RNA modification?

To protect mRNA from hydrolytic enzymes Signup and view all the answers

During peptide bond formation, which of the following occurs?

The amino acid is attached to the 3' end of the tRNA Signup and view all the answers

What is the role of initiation factors during translation?

To bring the small subunit to the ribosome Signup and view all the answers

What is the primary function of elongation factors during translation?

To facilitate the addition of amino acids to the growing polypeptide chain Signup and view all the answers

During translocation, what occurs?

The tRNA moves from the A site to the P site Signup and view all the answers

What is the energy source that allows the tRNA to shift from the A site to the P site during translocation?

GTP Signup and view all the answers

Which of the following is NOT a function of initiation factors during translation?

Releasing the completed polypeptide chain Signup and view all the answers

What is the result of the polypeptide chain being shifted from the A site to the P site during translation?

The polypeptide chain is lengthened by one amino acid Signup and view all the answers

Which of the following occurs during the elongation stage of translation?

The polypeptide chain is lengthened by one amino acid Signup and view all the answers

What is the result of the addition of a water molecule during translation?

The amino acid is hydrolyzed from the tRNA Signup and view all the answers

Study Notes

Translation

Polypeptide chain shifts from P site to A site, requiring energy from GTP.
Translocation: mRNA shifts one codon along the ribosome, allowing tRNA to shift from A site to P site and exit through E site.
Elongation continues until a stop codon reaches the A site.
Release factor binds to A site, causing hydrolysis and releasing the polypeptide chain.
Ribosomal subunits dissociate after termination.

Free and Bound Ribosomes

Free ribosomes synthesize proteins that function in the cytosol.
Bound ribosomes (attached to ER) synthesize proteins of the endomembrane system and secreted proteins.

Transcription

RNA synthesis is catalyzed by RNA polymerase.
RNA polymerase does not require a primer.
Base-pairing rules are the same as DNA, except uracil substitutes for thymine.
Transcription unit: a segment of DNA that is transcribed into a single RNA molecule.
Promoter: a sequence that RNA polymerase binds to.
Terminator: a sequence that signals the end of transcription.

Initiation Stage of Transcription

RNA polymerase binds to the promoter, opening up the DNA strand.
TATA Box is a sequence that RNA polymerase binds to.
RNA transcript is complementary to DNA, formed from 5' to 3'.

Elongation Stage of Transcription

RNA polymerase untwists the double helix.
Transcription occurs at a rate of 40 nucleotides per second in eukaryotes.
DNA is read 3' to 5', RNA transcript is formed 5' to 3'.

Termination Stage of Transcription

In bacteria, RNA polymerase stops transcription at the terminator.
In eukaryotes, RNA modification occurs, including 5' cap and 3' poly A tail.
Polyadenylation: poly A tail of RNA transcript that only has adenine bases on the 3' end.
5' cap: a modified nucleotide at the 5' end of mRNA.

Importance of RNA Modification

Protects mRNA from hydrolytic enzymes.
Helps ribosome attach to the 5' end.
Facilitates export.
If cap and tail are not present, RNA is hydrolyzed and loses function.

RNA Polymerase I

Synthesizes ribosomal RNA (rRNA).
In eukaryotes, rRNA has 4 components: 28S, 5.8S, 5S, and 18S.
Large subunit: 28S, 5.8S, and 5S.
Small subunit: 18S.

RNA Polymerase II

Synthesizes messenger RNA (mRNA).
Synthesizes small nucleolar RNA (snRNA) and micro RNA (miRNA).
miRNA is involved in RNA silencing and post-transcriptional regulation of genes.

RNA Polymerase III

Synthesizes transfer RNA (tRNA).
Synthesizes 5S rRNA.

RNA Splicing

Introns: non-coding regions.
Exons: coding regions.
RNA splicing removes introns by splicing at splice sites and joining exons by DNA ligase.
Bacterial cells have no introns, so no splicing is required.

Ribozymes

Ribozymes are enzymes that can splice RNA.
They can cleave and ligate RNA molecules.

Translation

Polypeptide chain shifts from P site to A site, requiring energy from GTP.
Translocation: mRNA shifts one codon along the ribosome, allowing tRNA to shift from A site to P site and exit through E site.
Elongation continues until a stop codon reaches the A site.
Release factor binds to A site, causing hydrolysis and releasing the polypeptide chain.
Ribosomal subunits dissociate after termination.

Free and Bound Ribosomes

Free ribosomes synthesize proteins that function in the cytosol.
Bound ribosomes (attached to ER) synthesize proteins of the endomembrane system and secreted proteins.

Transcription

RNA synthesis is catalyzed by RNA polymerase.
RNA polymerase does not require a primer.
Base-pairing rules are the same as DNA, except uracil substitutes for thymine.
Transcription unit: a segment of DNA that is transcribed into a single RNA molecule.
Promoter: a sequence that RNA polymerase binds to.
Terminator: a sequence that signals the end of transcription.

Initiation Stage of Transcription

RNA polymerase binds to the promoter, opening up the DNA strand.
TATA Box is a sequence that RNA polymerase binds to.
RNA transcript is complementary to DNA, formed from 5' to 3'.

Elongation Stage of Transcription

RNA polymerase untwists the double helix.
Transcription occurs at a rate of 40 nucleotides per second in eukaryotes.
DNA is read 3' to 5', RNA transcript is formed 5' to 3'.

Termination Stage of Transcription

In bacteria, RNA polymerase stops transcription at the terminator.
In eukaryotes, RNA modification occurs, including 5' cap and 3' poly A tail.
Polyadenylation: poly A tail of RNA transcript that only has adenine bases on the 3' end.
5' cap: a modified nucleotide at the 5' end of mRNA.

Importance of RNA Modification

Protects mRNA from hydrolytic enzymes.
Helps ribosome attach to the 5' end.
Facilitates export.
If cap and tail are not present, RNA is hydrolyzed and loses function.

RNA Polymerase I

Synthesizes ribosomal RNA (rRNA).
In eukaryotes, rRNA has 4 components: 28S, 5.8S, 5S, and 18S.
Large subunit: 28S, 5.8S, and 5S.
Small subunit: 18S.

RNA Polymerase II

Synthesizes messenger RNA (mRNA).
Synthesizes small nucleolar RNA (snRNA) and micro RNA (miRNA).
miRNA is involved in RNA silencing and post-transcriptional regulation of genes.

RNA Polymerase III

Synthesizes transfer RNA (tRNA).
Synthesizes 5S rRNA.

RNA Splicing

Introns: non-coding regions.
Exons: coding regions.
RNA splicing removes introns by splicing at splice sites and joining exons by DNA ligase.
Bacterial cells have no introns, so no splicing is required.

Ribozymes

Ribozymes are enzymes that can splice RNA.
They can cleave and ligate RNA molecules.

Translation

Polypeptide chain shifts from P site to A site, requiring energy from GTP.
Translocation: mRNA shifts one codon along the ribosome, allowing tRNA to shift from A site to P site and exit through E site.
Elongation continues until a stop codon reaches the A site.
Release factor binds to A site, causing hydrolysis and releasing the polypeptide chain.
Ribosomal subunits dissociate after termination.

Free and Bound Ribosomes

Free ribosomes synthesize proteins that function in the cytosol.
Bound ribosomes (attached to ER) synthesize proteins of the endomembrane system and secreted proteins.

Transcription

RNA synthesis is catalyzed by RNA polymerase.
RNA polymerase does not require a primer.
Base-pairing rules are the same as DNA, except uracil substitutes for thymine.
Transcription unit: a segment of DNA that is transcribed into a single RNA molecule.
Promoter: a sequence that RNA polymerase binds to.
Terminator: a sequence that signals the end of transcription.

Initiation Stage of Transcription

RNA polymerase binds to the promoter, opening up the DNA strand.
TATA Box is a sequence that RNA polymerase binds to.
RNA transcript is complementary to DNA, formed from 5' to 3'.

Elongation Stage of Transcription

RNA polymerase untwists the double helix.
Transcription occurs at a rate of 40 nucleotides per second in eukaryotes.
DNA is read 3' to 5', RNA transcript is formed 5' to 3'.

Termination Stage of Transcription

In bacteria, RNA polymerase stops transcription at the terminator.
In eukaryotes, RNA modification occurs, including 5' cap and 3' poly A tail.
Polyadenylation: poly A tail of RNA transcript that only has adenine bases on the 3' end.
5' cap: a modified nucleotide at the 5' end of mRNA.

Importance of RNA Modification

Protects mRNA from hydrolytic enzymes.
Helps ribosome attach to the 5' end.
Facilitates export.
If cap and tail are not present, RNA is hydrolyzed and loses function.

RNA Polymerase I

Synthesizes ribosomal RNA (rRNA).
In eukaryotes, rRNA has 4 components: 28S, 5.8S, 5S, and 18S.
Large subunit: 28S, 5.8S, and 5S.
Small subunit: 18S.

RNA Polymerase II

Synthesizes messenger RNA (mRNA).
Synthesizes small nucleolar RNA (snRNA) and micro RNA (miRNA).
miRNA is involved in RNA silencing and post-transcriptional regulation of genes.

RNA Polymerase III

Synthesizes transfer RNA (tRNA).
Synthesizes 5S rRNA.

RNA Splicing

Introns: non-coding regions.
Exons: coding regions.
RNA splicing removes introns by splicing at splice sites and joining exons by DNA ligase.
Bacterial cells have no introns, so no splicing is required.

Ribozymes

Ribozymes are enzymes that can splice RNA.
They can cleave and ligate RNA molecules.

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Description

This quiz covers the process of protein synthesis, including the translocation of mRNA and the roles of tRNA, GTP, and codons in elongation and termination.