Protein Synthesis

Translation

What is the process by which mRNA is translated into an amino acid sequence called?

What is the general structure of an amino acid composed of?

A central carbon, an amino group, a carboxyl group, a hydrogen atom, and a variable R group.

What forms the peptide bond between amino acids?

The carboxyl group of one amino acid reacts with the amino group of another, releasing water.

What do three nucleotides form in the genetic code?

A codon.

How does tRNA interact with the codon?

tRNA has an anticodon that is complementary to the codon on the mRNA.

How does tRNA become charged with an amino acid?

By an enzyme called aminoacyl-tRNA synthetase, which attaches the correct amino acid to its corresponding tRNA.

What are the A, P, and E sites in a ribosome?

A site: aminoacyl site, P site: peptidyl site, E site: exit site.

What happens at the A site of a ribosome?

A new tRNA carrying an amino acid enters and pairs with the mRNA codon.

What happens at the P site of a ribosome?

The growing polypeptide chain is held by tRNA.

What happens at the E site of a ribosome?

The empty tRNA exits the ribosome after releasing its amino acid.

What initiates translation in prokaryotes?

The small ribosomal subunit binds to the Shine-Dalgarno sequence.

What is the start codon in prokaryotes?

The first AUG after the Shine-Dalgarno sequence.

What do EF-T and EF-G factors do in prokaryotic translation?

EF-T helps bring tRNAs to the ribosome; EF-G helps translocate the ribosome along the mRNA.

What are release factors (EF-T, EF-G) responsible for in translation?

They recognize stop codons and promote ribosome dissociation.

What is a polysome?

A cluster of ribosomes translating the same mRNA simultaneously.

Why can bacteria couple transcription and translation?

Because both processes occur in the same location (cytoplasm) and happen simultaneously.

Can transcription and translation occur at the same time in eukaryotes?

No, because transcription occurs in the nucleus and translation occurs in the cytoplasm.

How does eukaryotic translation initiation differ from prokaryotic?

It forms at the 5' cap without a Shine-Dalgarno sequence, and the first AUG after the cap becomes the start site

Does translation end the same way for prokaryotes and eukaryotes?

Yes, it occurs when the ribosome encounters stop codon in the mRNA and the release factor recognize these stop condons

What is a tmRNA and its function in prokaryotes?

A tmRNA helps 'unstick' stalled ribosomes by providing a template for protein synthesis.

How do prokaryotes and eukaryotes slow or stop protein synthesis?

By using regulatory proteins, ribosome stalling, or mRNA degradation.

What do post-translational modifications to amino acids do?

They increase the type of functions and activities of proteins.

Name three types of post-translational modification.

Phosphorylation, glycosylation, ubiquitination.

What is the role of chaperonins in protein folding?

They assist in proper protein folding.

What is the difference between chaperonins that 'hold' and those that 'fold' proteins?

'Hold' chaperonins temporarily retain proteins; 'fold' chaperonins facilitate the folding process.

What does phosphorylation do

Adds a phosphate group to a protein, on amino acids like serine, threonine etc

What does Glycosyation do

Adds sugar molecules to proteins

What is the function of N’-terminal signal sequences in proteins?

They direct proteins to their correct cellular locations.

What happens to a protein labeled with ubiquitin?

It is tagged for degradation by the proteasome.

What does Ubiquitionation do

Marks the protein for recreation by the proteasome

what is a proteasome

A cells recycling bin