module 7 lec 6 Flashcards
What is the function of the ribosome?
The ribosome is the site of polypeptide synthesis.
What are ribosomes made of
Ribosomes are made of rRNA and proteins.
How do ribosomes contribute to translation?
Ribosomes read mRNA codons and facilitate the pairing of tRNA to add amino acids to the growing polypeptide chain.
What are the two main components of a ribosome?
Ribosomes have two main components: a large subunit and a small subunit.
Are ribosomes found in all cells?
Yes, ribosomes are found in both prokaryotic and eukaryotic cells, where they carry out translation.
What is translation initiation?
Translation initiation is the process where the ribosome assembles on the mRNA and starts protein synthesis.
What are the key steps in translation initiation?
Small ribosomal subunit binds to mRNA.
Initiator tRNA binds to the start codon (usually AUG).
The large ribosomal subunit binds, forming the complete ribosome.
What role does the start codon play in translation initiation?
The start codon (AUG) signals the beginning of translation and recruits the initiator tRNA carrying methionine.
What is the role of the initiator tRNA in translation initiation?
The initiator tRNA carries the first amino acid (usually methionine) and pairs with the start codon on mRNA.
What happens after translation initiation
After initiation, the ribosome moves along the mRNA, and translation elongation begins, adding amino acids to the growing polypeptide chain.
What happens during translation elongation?
During translation elongation, amino acids are added to the C-terminus of the growing polypeptide chain.
How are amino acids added during elongation?
tRNA molecules with the corresponding amino acids bind to mRNA codons in the ribosome, and the amino acids are added to the polypeptide.
What is the direction of polypeptide growth during translation elongation?
The polypeptide grows in the C-terminus direction as amino acids are added one by one.
What are the key steps in translation elongation?
Key steps include:
Codon recognition: tRNA with the matching anticodon binds to the mRNA codon.
Peptide bond formation: The ribosome catalyzes the formation of a peptide bond between amino acids.
Translocation: The ribosome moves along the mRNA to the next codon.
What happens after translation elongation?
After elongation, the process continues until a stop codon is reached, triggering translation termination.
What signals the end of translation?
Stop codons (UAA, UAG, UGA) signal the end of translation and trigger translation termination.
What happens during translation termination?
During translation termination, the ribosome reaches a stop codon, and a release factor binds, causing the release of the newly synthesized polypeptide.
What role do release factors play in translation termination?
Release factors recognize the stop codon and catalyze the release of the polypeptide from the ribosome.
What happens to the ribosome after translation termination?
After translation termination, the ribosome dissociates from the mRNA, and the polypeptide is released to fold into its functional form.
What is a polyribosome?
A polyribosome is a complex of multiple ribosomes translating the same mRNA simultaneously.
What is the advantage of polyribosomes in translation?
Polyribosomes increase the efficiency of protein synthesis by allowing multiple copies of a protein to be made at once from a single mRNA.
Where are polyribosomes typically found?
Polyribosomes are commonly found in the cytoplasm of both prokaryotes and eukaryotes, where they speed up protein production.
What is posttranslational processing?
Posttranslational processing involves modifications to a protein after it has been synthesized, affecting its structure, activity, and function.
How does enzymatic cleavage affect proteins?
Enzymatic cleavage may remove an amino acid, split a polyprotein, or activate a zymogen (inactive enzyme form)
What is the role of chemical modifications in posttranslational processing?
Chemical modifications like phosphorylation, acetylation, or glycosylation can alter protein structure, activity, or its cellular location.
What is a zymogen?
A zymogen is an inactive enzyme precursor that is activated by posttranslational cleavage.
How do chemical modifications affect protein function?
Chemical modifications can enhance or inhibit a protein’s function, affect its stability, or influence its interaction with other molecules
What is polyprotein cleavage?
Polyprotein cleavage involves splitting a large protein into smaller functional proteins after translation, often seen in viral proteins.
Where does gene expression occur in prokaryotes?
In prokaryotes, gene expression occurs in the cytoplasm since they lack a nucleus.
How is transcription and translation related in prokaryotes?
In prokaryotes, transcription and translation can occur simultaneously in the cytoplasm
What is the key regulatory element for gene expression in prokaryotes?
Prokaryotes regulate gene expression using operons, which group related genes together under the control of a single promoter.
Do prokaryotes have introns in their genes?
No, prokaryotes typically do not have introns in their genes, so mRNA is usually ready for translation right after transcription.
Where does transcription and translation occur in eukaryotes?
In eukaryotes, transcription occurs in the nucleus, and translation happens in the cytoplasm.
What is the key regulatory element for gene expression in eukaryotes?
: In eukaryotes, gene expression is regulated by promoters, enhancers, silencers, and other regulatory sequences that interact with transcription factors.
How is RNA processed in eukaryotes?
n eukaryotes, RNA undergoes several post-transcriptional modifications like capping, splicing, and the addition of a poly-A tail before leaving the nucleus.
How is gene expression in eukaryotes more complex than in prokaryotes
Eukaryotic gene expression is more complex due to chromatin remodeling, RNA processing, and regulation by multiple factors, including enhancers and repressors.
Do eukaryotes have introns?
Yes, eukaryotic genes often contain introns that are removed during RNA splicing, leaving only the exons in the mature mRNA.
