Molecular and Cellular Basis of Life: Protein Synthesis

Vocabulary-based flashcards covering the molecular mechanisms of translation, the genetic code, and the differences between prokaryotic and eukaryotic protein synthesis.

Adaptor Hypothesis

Proposed by Crick around 1954, it states that a template is RNA and the amino acid is carried to the template by an adaptor molecule that may contain nucleotides.

tRNA (Transfer RNA)

A molecular adaptor that brings amino acids to the mRNA; it contains an amino acid binding site and an anticodon.

Anticodon

A nucleotide triplet on tRNA that pairs with a complementary codon on mRNA during translation.

Degenerate

A property of the genetic code where most amino acids are specified by two to four (or up to six) different codons.

Frameshift mutation

An alteration of the reading frame caused by the insertion or deletion of one or two bases.

AUG

The initiation codon that establishes the reading frame and codes for methionine.

Stop codons

The three codons ($UAA$, $UGA$, and $UAG$) that signal the termination of a polypeptide chain.

Open Reading Frame (ORF)

A sequence characterized by an $AUG$ codon followed by a long stretch of amino acid-coding codons without a stop codon.

Wobble hypothesis

The theory that the first base of the anticodon can tolerate more mispairing, allowing the same tRNA to recognize different codons.

70S Ribosome

The prokaryotic ribosome composed of a $50S$ large subunit and a $30S$ small subunit.

80S Ribosome

The eukaryotic ribosome composed of a $60S$ large subunit and a $40S$ small subunit.

A site (aminoacyl site)

The ribosomal binding site for the incoming aminoacyl-tRNA.

P site (peptidyl site)

The ribosomal binding site occupied by the tRNA with the growing polypeptide chain attached.

E site (exit site)

The ribosomal binding site where the "empty" tRNA resides before being released.

Aminoacyl-tRNA synthetases

A set of twenty enzymes that each bind a specific amino acid and its matching tRNA to perform aminoacylation.

Shine-Dalgarno sequence

An mRNA sequence in prokaryotes recognized by the $16S$ rRNA of the small ribosomal subunit to initiate translation.

Kozak sequence

The sequence that serves as the translation initiation site in eukaryotes.

tRNAfMet

The initiator tRNA in prokaryotes that carries N-Formylmethionine.

EF-Tu

An elongation factor that carries the activated tRNA to the ribosomal A site and is recharged by EF-Ts.

Peptidyl transferase

An enzymatic activity carried out by the $23S$ rRNA in prokaryotes that forms the peptide bond between amino acids.

EF-G

An elongation factor that energizes ribosome translocation through the hydrolysis of $GTP$.

Release factors (RF1, RF2, RF3)

Proteins that recognize stop codons and trigger the hydrolysis of the terminal peptide-tRNA bond and ribosome dissociation.

Polycistronic mRNA

An mRNA molecule that carries the genetic information for multiple different proteins, characteristic of prokaryotes.

Monocistronic mRNA

An mRNA molecule that codes for only a single protein, characteristic of eukaryotes.