20 Questions
Which component of the ribosome binds peptidyl-tRNA?
Peptidyl (P)
In which direction does the ribosome read mRNA during protein synthesis?
5'->3'
What is the primary function of transcription in the process of protein synthesis?
Synthesis of mRNA from DNA
In prokaryotes, when can translation of mRNA begin?
Before transcription has finished
What is the function of peptidyl-transferase during polypeptide chain elongation in translation?
Catalyzing the formation of peptide bonds between amino acids
What is the role of the release factor in termination and release during translation?
Binding to the stop codon in the A site
What is the significance of the stop codons UAA, UAG, and UGA during translation?
They signal termination of protein synthesis
What occurs during folding and post-translational modifications of peptides?
Formation of disulfide bonds and attachment of prosthetic groups
During protein biosynthesis, what is responsible for attaching the correct amino acid to the correct tRNA, using ATP energy?
Aminoacyl-tRNA synthetases
What is the role of N-formyl methionyl-tRNA in the initiation complex of protein biosynthesis in prokaryotes?
Serving as the start codon
Which component of the ribosome binds the incoming aminoacyl-tRNA to the A site during elongation in protein biosynthesis?
Ribosomal RNA (rRNA)
What occurs when the ribosome moves one codon towards the 3’ end of the mRNA during elongation in protein biosynthesis?
Translocation
Which stage of protein biosynthesis involves the activation of amino acids to facilitate formation of a peptide bond and their linkage to the mRNA that encodes them?
Activation of Amino Acids
During initiation in eukaryotic cells, what binds eukaryotic mRNAs to the ribosome as a complex with specific binding proteins?
Eukaryotic initiation factors (eIF)
What forms a catalytic domain for polypeptide synthesis when engaged with mRNAs in ribosomes?
(rRNA)-protein complexes
What is redundant but not ambiguous in the genetic code during protein biosynthesis?
(mRNA) codons
Which molecule is responsible for forming attachments to individual amino acids and recognizing the encoded sequences of mRNAs during protein biosynthesis?
(tRNA)
What is activated to facilitate formation of a peptide bond and linked to the mRNA that encodes it during protein biosynthesis?
Amino acids
What is formed as a result of Amino acid + tRNA + ATP + Mg2+ reaction during protein biosynthesis?
Aminoacyl-tRNA
What does each codon specify in the genetic code during protein biosynthesis?
An amino acid
Study Notes
- Transfer RNA (tRNA) forms attachments to individual amino acids and recognize the encoded sequences of mRNAs to allow correct insertion of amino acids into the elongating polypeptide chain.
- Ribosomal RNA (rRNA) assembles with ribosomal proteins to form ribosomes. Ribosomes engage mRNAs, forming a catalytic domain for polypeptide synthesis. Each codon specifies an amino acid, the genetic code is redundant but not ambiguous.
- Protein biosynthesis occurs in five stages: activation of amino acids, initiation, elongation, termination, and folding and posttranslational processing.
- Activation of Amino Acids:*
- Each amino acid must be activated to facilitate formation of a peptide bond and linked to the mRNA that encodes it.
- Amino acid + tRNA + ATP + Mg2+ results in the formation of aminoacyl-tRNA.
- Aminoacyl-tRNA synthetases are responsible for attaching the correct amino acid to the correct tRNA, using ATP energy.
- Initiation:*
- Formation of the initiation complex in bacteria.
- AUG (methionine) start codon binds to formyl methionine tRNA in prokaryotes, while methionine tRNA binds in eukaryotes.
- Initiating factors (IF), ribosome, mRNA, and N-formyl methionyl-tRNA form the initiation complex.
- Initiation in eukaryotic cells: eukaryotic mRNAs bound to the ribosome as a complex with specific binding proteins.
- Eukaryotic initiation factors (eIF) including eIF4F, eIF4E, eIF4G, and eIF4A.
- Elongation:*
- Involved in the formation of peptide bonds between amino acids.
- Incoming aminoacyl-tRNA binds to the A site of the ribosome, anticodon to codon.
- Translocation: ribosome moves one codon towards the 3’ end of the mRNA and shifts P-site tRNA to the E site.
- Peptide bond formed between the 2 amino acids bound by their tRNAs to the A and P sites on the ribosome.
Test your knowledge of protein synthesis with this quiz focusing on the components of ribosomes, the reading of mRNA, and the three tRNA binding sites. Explore the central dogma of biology and understand the process of one gene encoding for one protein.
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