Biology RNA and Protein Synthesis Quiz

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Questions and Answers

What type of bond is formed between an amino acid and its tRNA?

Phosphodiester bond

Ionic bond

Covalent bond (correct)

Hydrogen bond

Which part of the tRNA molecule contains the anticodon?

5' end

Amino acid-accepting arm

Anticodon loop (correct)

3' end

What is the role of aminoacyl-tRNA synthetase?

To attach amino acids to mRNA

To break down tRNA molecules

To link amino acids to the correct tRNA (correct)

To form peptide bonds between amino acids

What is the significance of the high-energy bond formed between the amino acid and tRNA?

It is used to link the amino acid to the polypeptide chain Signup and view all the answers

What is the amino acid-accepting arm of the tRNA?

The single-stranded region at the 3’ end where the amino acid Attaches Signup and view all the answers

How many aminoacyl-tRNA synthetases are there in a cell?

20 Signup and view all the answers

In the context of wobble base pairing, which position of the anticodon allows for some flexibility in base pairing?

Third position Signup and view all the answers

What is the purpose of the redundancy in the genetic code?

To allow a single amino acid to be coded by multiple codons Signup and view all the answers

What structural feature is formed by double-stranded regions in tRNA?

Loops and folds Signup and view all the answers

What would be the consequence if there was no redundancy in the genetic code?

Each codon would code for a unique amino acid Signup and view all the answers

During gene transcription, what is the primary role of RNA polymerase?

To catalyze the formation of phosphodiester bonds between RNA nucleotides. Signup and view all the answers

Which type of RNA polymerase is responsible for transcribing mRNA in eukaryotes?

RNA Polymerase II Signup and view all the answers

What is the major difference between eukaryotic and prokaryotic RNA polymerases?

Eukaryotes have three different RNA polymerases, while prokaryotes use only one. Signup and view all the answers

What role does phosphorylation of RPB1 subunit play in RNA Polymerase II activity?

It regulates the enzyme's activity during transcription Signup and view all the answers

What is the role of transcription factors in conjunction with RNA Polymerase II?

To help RNA polymerase 'read' DNA and bind to it. Signup and view all the answers

Which of the following is NOT a function of RNA Polymerase II?

Creating the primer to start RNA synthesis. Signup and view all the answers

Where does the folding of polypeptide chains into the active protein occur?

In the cytoplasm, mitochondria, nucleus, and ER. Signup and view all the answers

What is the direct product of translation?

A polypeptide chain Signup and view all the answers

What is the primary role of transcription factors (TF) in the initiation of transcription?

To guide RNA Polymerase II to the core promoter region. Signup and view all the answers

Which event directly initiates transcription after the pre-initiation complex is formed?

Phosphorylation of RNA Polymerase II at RBP1. Signup and view all the answers

What is the function of the 'transcription bubble' formed during transcription elongation?

To create two separate strands of DNA necessary for RNA synthesis. Signup and view all the answers

During transcription, what determines which DNA strand serves as the template for RNA synthesis?

The location of the core promoter sequence. Signup and view all the answers

What is the primary role of the AAUAAA hexamer sequence in transcription?

To signal the termination of transcription. Signup and view all the answers

How does protein translation differ from transcription in terms of 'language'?

Translation converts 'RNA language' into 'protein language'. Signup and view all the answers

How many nucleotides are present in a codon?

Three Signup and view all the answers

Why is the genetic code considered 'redundant'?

Because there are more codons than amino acids. Signup and view all the answers

What is the dual role of the codon AUG in protein synthesis?

It codes for the amino acid methionine and signals for translation initiation. Signup and view all the answers

What is the significance of the 3D structure of tRNA molecules?

It enables tRNA molecules to specifically bind to both mRNA and amino acids. Signup and view all the answers

What is the role of ribosomes in protein translation?

They assemble amino acids into a polypeptide chain. Signup and view all the answers

Which subunit of the ribosome matches tRNA to the mRNA codon?

Small subunit Signup and view all the answers

How does the large subunit of the ribosome contribute to protein synthesis?

It forms covalent bonds between amino acids. Signup and view all the answers

What characterizes wobble base-pairing in tRNA?

It can tolerate a mismatch at the third position. Signup and view all the answers

What is the composition by weight of ribosomes?

2/3 RNA and 1/3 proteins Signup and view all the answers

Which of the following statements about ribosomal RNA (rRNA) is true?

It is responsible for the catalytic activity and regulation of translation. Signup and view all the answers

What is the function of free ribosomes in protein synthesis?

To translate proteins that remain in the cytoplasm or mitochondria. Signup and view all the answers

What does the sedimentation coefficient (S) of ribosomal subunits indicate?

The size and density of the ribosomal particles. Signup and view all the answers

Which site in the ribosome is responsible for accepting a tRNA carrying the next amino acid to be added to the polypeptide chain?

A site Signup and view all the answers

Which of the following DOES NOT contribute to the assembly of the ribosome on the mRNA?

RNA polymerase Signup and view all the answers

How does the ribosome "know" where to start translation on the mRNA?

The ribosome binds to the 5' end of the mRNA and scans for the start codon. Signup and view all the answers

What is the role of the peptidyl transferase activity in protein synthesis?

It catalyzes the formation of peptide bonds between amino acids. Signup and view all the answers

Which of the following is NOT a stop codon?

UAU Signup and view all the answers

What happens when the ribosome encounters a stop codon in the mRNA?

The ribosome releases the mRNA and separates into its two subunits. Signup and view all the answers

What is the role of the tRNA in protein synthesis?

It carries amino acids to the ribosome and matches them to the appropriate mRNA codons. Signup and view all the answers

What is the role of proteins called "translation initiation factors" in protein synthesis?

They help to recruit the small ribosomal subunit to the mRNA. Signup and view all the answers

What is the role of the small ribosomal subunit in protein synthesis?

It binds to the mRNA and scans for the start codon. Signup and view all the answers

Where does protein synthesis occur in the cell?

Cytoplasm Signup and view all the answers

What is the function of the mRNA-binding site of the ribosome?

It binds to the mRNA molecule. Signup and view all the answers

Which of the following statements is true about protein synthesis?

Protein synthesis is initiated by the binding of the large ribosomal subunit to the mRNA. Signup and view all the answers

What is the difference between translation elongation and translation termination?

Elongation involves the addition of amino acids to the polypeptide chain, while termination involves the release of the completed polypeptide chain from the ribosome. Signup and view all the answers

Study Notes

RNA Transcription & Translation

RNA transcription is the process of copying information from a DNA strand into an RNA molecule.
RNA polymerase enzymes catalyze this process.
Eukaryotes have three RNA polymerases.
- RNA Pol I transcribes ribosomal RNA (rRNA).
- RNA Pol II transcribes messenger RNA (mRNA) and most non-coding RNAs.
- RNA Pol III transcribes transfer RNA (tRNA) and other types.
Prokaryotes use only one RNA polymerase.
RNA polymerase II (RNA Pol II) is a large multiprotein complex composed of 12 subunits (RBP1-12).
RPB1 subunit catalyzes transcription of DNA to mRNA.
Phosphorylation of RBP1 regulates enzyme activity.
RNA Pol II needs transcription factors for DNA binding and transcription.
RNA Pol II can start creating an RNA chain without a primer.

Gene Transcription

This process copies DNA information into an RNA molecule.
It is catalyzed by RNA polymerase enzymes.

From DNA to protein

DNA is transcribed into mRNA in the nucleus.
mRNA is released into the cytoplasm through nuclear pores.
mRNA is attached to ribosomes.
Ribosomes translate mRNA into a polypeptide chain.
Polypeptide chains fold into an active protein conformation.
Folding occurs in the cytoplasm, mitochondria, nucleus, and ER.

Transcription Initiation:

RNA Pol II binds to a non-coding DNA sequence (core promoter).
Transcription factors (TF) guide RNA Pol II to the core promoter.
RNA Pol II and TF form the pre-initiation complex.
RNA Pol II phosphorylation at RBP1 initiates transcription.

Transcription Elongation:

RNA Pol II unwinds the DNA strand into a transcription bubble.
RNA Pol II moves along one strand, using it as a template to synthesize a complementary RNA sequence.
Either of DNA strands can be template (depending on promoter location).
RNA Pol II adds nucleotides to the 3' end of the growing RNA molecule.

Transcription Termination:

RNA Pol II encounters a termination signal (AAUAAA hexamer).
Transcription stops.
RNA polymerase and mRNA are released.
The DNA double helix reforms.

Protein Translation - Reading the code

The process converts RNA language into protein language.
The process uses different symbols.

Codons

mRNA is read in groups of three nucleotides called codons.
Each codon corresponds to a specific amino acid.
There are 64 possible codons.
Only 20 amino acids.
Redundancy in the code
AUG is the start codon for methionine.
There are three stop codons.

Transfer RNAs (tRNAs)

Small RNA molecules.
Folded into a cloverleaf shape.
80 nucleotides long
The strand folds into complex 3D structures.
Different parts bind.
Amino acid attachment site
Anticodon loop

Coupling of amino acids to tRNAs

Aminoacyl-tRNA synthetases catalyze the process.
One synthetase for each amino acid.
The enzyme recognizes the nucleotide sequence in the anticodon loop of a specific tRNA and the amino acid that corresponds to the codon sequence.
An enzymatic reaction links the amino acid to the tRNA.
Energy from ATP hydrolysis is used.
A high energy bond links amino acid and tRNA.

Wobble base-pairing and redundancy

The third nucleotide in the anticodon (wobble position) can sometimes tolerate a mismatch with the corresponding nucleotide in the mRNA codon (doesn't follow strict base pairing rules).
Certain amino acids are encoded by more than one codon.
This redundancy occurs because some amino acids can bind to more than one tRNA.

Ribosomes Translate mRNA into Protein

mRNA is released from the nucleus
Attaches to ribosomes.
Ribosomes translate mRNA into proteins.
Free ribosomes remain in the cytoplasm.
Endoplasmic reticulum ribosomes translate proteins destined for the cell membrane or release by the cell.

Ribosomes

Protein translation is carried out by ribosomes.
Ribosomes bind to mRNA molecules and position correct tRNAs.
Ribosomes catalyze the formation of covalent bonds between amino acids (peptidyl transferase activity).
Ribosomes are large complexes made of ribosomal proteins and ribosomal RNAs.
Ribosomes are made of a large and a small subunit.
Small subunit matches tRNA to the mRNA codon.
Large subunit catalyzes peptide bonds between amino acids.
Ribosomes have 40S (small) and 60S (large) subunits = 80S

Ribosome Structure

Ribosomes have 2/3 RNA and 1/3 proteins by weight.
RNA, not protein, is responsible for catalytic activity and regulation.
RNA is folded into a precise 3D structure.
Binding sites for tRNAs
Catalytic site of peptidyl transferase.
RNA molecules can act as enzymes (ribozymes).

Ribosome Function

Small and large ribosome subunits assemble on an mRNA molecule.
Ribosomes translate mRNA from the 5' to 3' direction, translating one codon at a time. Using tRNAs as adaptors.
Each amino acid is added to the end of the polypeptide chain in the correct sequence.
Two subunits separate when protein synthesis completes.

Mechanism of Protein Translation

Translation initiation

The tRNA recognizing the start codon (initiator tRNA) binds to the small ribosomal subunit.
This scans the mRNA until it finds the start codon (AUG) and binds to it
The large subunit (after scanning) completes ribosome assembly.
Initiator tRNA always carries methionine.
The small subunit binds to the 5′ end of the mRNA and scans until it detects AUG.
The anticodon of the initiator tRNA base pairs with the AUG codon.

Translation elongation

The ribosome moves in a 5' to 3′ direction translating the nucleotide sequence into an amino acid sequence, one codon at a time, using the tRNAs as adaptors.
Amino acids are added in the correct sequence to the end of the polypeptide chain.

Translation termination

The presence of a stop codon (UAA, UAG, or UGA) signals protein synthesis termination.
Proteins called release factors bind to the stop codons in the A site.
Binding of release factors changes peptidyl transferase activity.
Water molecule is added (hydrolysis).
The C-terminal polypeptide is released from tRNA.
Ribosome releases mRNA, dissociates into subunits.

Ribosome Binding Sites

mRNA-binding site
Aminoacyl-tRNA (A) site
Peptidyl-tRNA (P) site
Exit (E) site

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Description

Test your knowledge on the key concepts of RNA and protein synthesis, including the role of tRNA, aminoacyl-tRNA synthetase, and the mechanisms behind gene transcription. This quiz covers essential topics around the structure and function of RNA as well as the genetic code. Perfect for students studying molecular biology or related fields.