Translation and Protein Destination Lecture Flashcards

Flashcards covering the major components, stages, and fate of polypeptides during and after translation according to Chapter 17 notes.

Eukaryotic Translation Locations

In eukaryotes, translation occurs in the cytoplasm, on the rough ER, in the mitochondrial matrix, and in the chloroplast stroma.

Genetic Code

The universal key to translating nucleotide sequences to amino acids, shared by nearly all organisms and made of 3-nucleotide sequences called codons.

Codon

A sequence of 3 nucleotides that encodes a specific amino acid; there are 64 total ($4^3$) possible combinations.

Genetic Code Redundancy

A property of the genetic code where most amino acids have more than one codon; 61 codons encode for 20 amino acids, while 3 serve as stop codons.

Ribosome Subunits

Consist of a large subunit and a small subunit, both composed of ribosomal RNAs (rRNAs) and proteins.

Transfer RNAs (tRNAs)

RNAs that carry specific amino acids and bind to mRNA codons; they contain an amino acid attachment site at one end and an anticodon at the other.

Anticodon

A region on the tRNA that binds antiparallel to its amino acid's specific mRNA codon using base pair rules.

Aminoacyl-tRNA Synthetase

The enzyme responsible for attaching the correct amino acid to each specific tRNA type.

A Site

The ribosome binding site for the incoming aminoacyl-tRNA (AA-tRNA).

P Site

The ribosome binding site for the tRNA carrying the growing polypeptide chain.

E Site

The exit site on the ribosome for empty tRNAs.

Translation Initiation

The stage where the small ribosomal subunit and initiator tRNA (Met-tRNA) bind the $5'$ end of mRNA and scan towards the $3'$ for the first AUG start codon.

Reading Frame

The specific choice of nucleotide triplet groups for translation; although 3 frames are possible, only one is correct.

Translation Elongation

The process where codons are read, peptide bonds form between amino acids, and the growing chain is transferred to the A site tRNA, adding amino acids to the C-terminus.

Ribozyme

In the context of translation, an rRNA that catalyzes the formation of peptide bonds, powered by GTP hydrolysis.

Untranslated Regions (UTRs)

Segments of the mRNA that exist on either side of the protein-coding region, which spans from the first start codon to the first in-frame stop codon.

Translation Termination

Occurs when a stop codon (UAG, UAA, or UGA) at the A site binds a release factor, causing the release of the polypeptide and the separation of ribosome subunits.

Release Factor

A protein that binds to the stop codon at the A site and releases the new polypeptide from the tRNA at the P site.

Post-translational Modification

Chemical changes after translation, including folding, the removal of amino acids (e.g., insulin), or the covalent attachment of groups such as sugars to form glycoproteins.

Signal Sequence

A molecular shipping label at the N-terminal of a polypeptide that causes the ribosome to bind to the Rough ER membrane pore.

Signal-recognition particle (SRP)

A particle in the cytosol that recognizes and binds the signal peptide of a growing polypeptide chain.

Stop Transfer Sequence

A hydrophobic region in a polypeptide that stays in the lipid bilayer, required for plasma membrane proteins.