Biological Translation and Ribosome Function

Flashcards covering translation initiation, elongation, termination, and regulatory mechanisms in prokaryotes and eukaryotes based on the lecture transcript.

Synthetic versus biological peptide bond formation speed

Synthetic machines like the ammodator form peptide bonds at a rate of one every __________ minutes, whereas biological cells complete the same task in seconds.

Directionality of protein synthesis

The construction of polypeptides occurs in a specific order, building from the __________ terminus to the __________ terminus.

Bacterial ribosome subunit Sedimentation coefficients

Bacterial ribosomes consist of a large __________ subunit and a small __________ subunit.

Ribosomal tRNA processing sites

The three key sites within a ribosome are the __________ site (aminoacyl), the __________ site (peptidyl), and the __________ site (exit).

The catalytic component of the ribosome

Inside the ribosome, the catalytic work of forming peptide bonds is performed by the __________ component rather than the protein component.

Bacterial initiator tRNA

The specialized amino acid carrier used for the first codon in bacteria is called __________, which represents a formulated methionine.

Bacterial mRNA positioning sequence

The __________ sequence in bacterial mRNA interacts with the __________ rRNA of the small ribosomal subunit to identify the translation start site.

Premature ribosome assembly blockers

The initiation factors __________ and __________ function to block the premature assembly of the complete 70S ribosome.

Initiator tRNA escort protein

The GTPase protein __________ is responsible for escorting the special fMet-tRNA to the exposed AUG codon in the P site.

The 30S pre-initiation complex

The __________ complex is formed once IF2 has escorted the fMet-tRNA to the small subunit, but before the large subunit joins.

Elongation factor EF-Tu

The abundant GTPase protein __________ binds to and protects the ester linkage of charged tRNAs while escorting them to the A site.

Elongation factor EF-Ts

The protein __________ is responsible for resetting EF-Tu by replacing its bound GDP with GTP.

Peptidyl transferase center catalysis

Peptide bond formation occurs at the peptidyl transferase center, primarily catalyzed by the __________ rRNA of the large subunit.

Elongation factor EF-G

The GTP-binding protein __________ is required for translocation, providing the mechanical "shove" to move the ribosome three nucleotides downstream.

Standard stop codons

In the nearly universal genetic code, the three stop codons are __________, __________, and __________.

Termination proteins

Stop codons are recognized by proteins known as __________ (such as RF1 and RF2) rather than by tRNAs.

Eukaryotic cap-binding protein

In eukaryotic translation initiation, the factor __________ binds to the 5' cap of the mRNA to help identify the start of the transcript.

Eukaryotic start site identification

Eukaryotes find the appropriate start site by having the small subunit and initiator tRNA __________ the mRNA from the 5' end toward the 3' end using an ATP-dependent __________.

Eukaryotic mRNA circularity

Eukaryotic mRNAs are functionally circularized when the __________ binding protein at the 3' tail interacts with bridge proteins connected to the 5' cap.

The antibiotic Puromycin

The antibiotic __________ acts by mimicking an aminoacyl-tRNA, attaching to the growing peptide chain and causing abortive, premature termination.

Signal recognition particle (SRP) function

The __________ is a ribonucleoprotein that binds to an alpha-helical signal sequence on a nascent peptide, halting translation until the ribosome reaches the ER.

Iron storage protein

The protein __________ consists of 24 subunits and forms a hollow ball capable of sequestering thousands of iron atoms.

Ferritin translation regulation

In the presence of high iron, the __________ binds to iron and dissociates from the mRNA, allowing the translation of ferritin to proceed.

Transferrin receptor mRNA stability

During conditions of low iron, the IREBP binds to the 3' UTR of the transferrin receptor mRNA, which __________ the transcript and increases receptor production.

How is the appropriate AUG start site found in prokaryotes? A) By recognizing a poly-A tail B) By the interaction of the Shine-Dalgarno sequence with rRNA C) By scanning for the start codon from 5' to 3' D) By binding to a cap structure

B

What elongation factors are involved in elongation and what roles do they perform? A) EF1 and EF2 B) EF-Tu and EF-G C) IF1 and IF2 D) RF1 and RF2

B

Which subunit initially binds mRNA and where is the PTC located? A) The large subunit, in the A site B) The small subunit, in the PTC C) The small subunit, in the large subunit D) The small subunit, in the large ribosomal subunit

D

What is the role of the Shine-Dalgarno sequence? A) To initiate translation in eukaryotes B) To align the ribosome with the start codon C) To enhance mRNA stability D) To terminate translation

B

Outline the steps in prokaryotic initiation involving IF2. A) IF2 synthesizes mRNA B) IF2 escorts fMet-tRNA to the small subunit C) IF2 attaches to the large subunit D) IF2 binds to the A site of the ribosome

B

Which elongation factors are GTPases? A) EF-Tu and EF-Ts B) IF1 and IF2 C) EF-Tu and EF-G D) RF1 and RF2

C

What are the A, P, and E sites in a translating ribosome? A) Sites for aminoacyl-tRNA binding, peptide bond formation, and release B) Sites for mRNA binding only C) Sites for ribosomal RNA synthesis D) Sites for termination of translation only

A

What is the initiating tRNA in prokaryotes and what is distinctive about it? A) tRNA^Tyr, it carries tyrosine B) tRNA^Met, it's unmodified C) fMet-tRNA, it carries a formulated methionine D) tRNA^Gly, it binds glycine

C

What is the PTC and what does it catalyze? Who attacks whom? A) The active site for tRNA binding B) The peptidyl transferase center that catalyzes peptide bond formation C) The site for termination of translation D) A regulatory site for ribosome function

B

What is translocation and why is it necessary for continued translation? A) It allows the ribosome to pause during translation B) It moves the ribosome along the mRNA strand C) It terminates the translation process D) It stabilizes the mRNA

B

What is the role of SRP in the secretory pathway? A) It propels the ribosome forward B) It halts translation and delivers peptides to the ER C) It aids in mRNA degradation D) It synthesizes proteins from scratch

B

Understand iron-based regulation of transferrin receptor and ferritin translation. A) High iron stabilizes transferrin receptor mRNA B) Low iron enhances ferritin degradation C) High iron allows ferritin translation to proceed D) Low iron destabilizes all mRNAs

C

Know highlighted differences between prokaryotic and eukaryotic translation. A) Both use the same initiation factors B) Prokaryotic translation occurs in the nucleus C) Eukaryotic translation uses a 5' cap and scanning for the start codon D) Prokaryotic translation relies on 5' capping

C