Expression of Proteins (Translation) – Key Vocabulary

A set of vocabulary flashcards covering the major molecules, steps, and post-translational events involved in eukaryotic protein synthesis.

Translation

The cytoplasmic process in which ribosomes use the nucleotide sequence of mRNA to assemble a specific sequence of amino acids into a polypeptide.

mRNA (messenger RNA)

Single-stranded RNA that carries the genetic information transcribed from DNA and provides the codon sequence read during translation.

Ribosome

A 40S/60S two-subunit ribonucleoprotein complex that binds mRNA and tRNAs to catalyse protein synthesis.

Polysome

A cluster of multiple ribosomes simultaneously translating the same mRNA molecule.

Codon

A sequence of three nucleotides in mRNA that specifies either one amino acid or a stop signal.

Genetic Code

The set of 64 codons—61 coding for 20 amino acids and 3 acting as stop signals—that translates nucleotide information into protein sequence.

Start Codon (AUG)

The codon that establishes the reading frame and recruits methionine-charged tRNA to begin translation.

Stop Codon

One of three codons (UAA, UAG, UGA) that signal termination of polypeptide elongation.

Reading Frame

The non-overlapping, triplet grouping of nucleotides set by the start codon and maintained during translation.

Open Reading Frame (ORF)

The stretch of nucleotides between a start codon and a stop codon that can be translated into protein.

tRNA (transfer RNA)

A 76-90 nucleotide adaptor molecule with an anticodon loop and 3′ acceptor end that delivers specific amino acids to the ribosome.

Anticodon

The three-nucleotide sequence on tRNA that base-pairs with a complementary mRNA codon.

Aminoacyl-tRNA Synthetase

One of 20 enzymes that couples a specific amino acid to its corresponding tRNA using ATP, forming aminoacyl-tRNA.

Charging (Aminoacylation)

The ATP-dependent attachment of an amino acid to its tRNA by aminoacyl-tRNA synthetase.

Aminoacyl-tRNA

A tRNA covalently linked to its correct amino acid; the substrate used by the ribosome during elongation.

Peptidyl Transferase

The ribosomal rRNA-based enzymatic activity that forms peptide bonds between adjacent amino acids during elongation.

Initiation (Translation)

Assembly of the small and large ribosomal subunits on mRNA, recognition of the start codon, and binding of Met-tRNA to the P site.

Elongation (Translation)

Cyclic process in which aminoacyl-tRNAs enter the A site, peptide bonds form, and the ribosome translocates along mRNA.

Termination (Translation)

Stage where a stop codon recruits release factors, prompting polypeptide release and ribosome recycling.

Central Dogma of Molecular Biology

Concept that genetic information flows from DNA → RNA → Protein, with replication, transcription, and translation as main transfers.

Protein Folding

The post-translational process whereby a nascent polypeptide acquires its native three-dimensional structure via non-covalent interactions and disulfide bonds.

Disulfide Bond

A covalent linkage between two cysteine residues stabilising tertiary or quaternary protein structure.

Post-translational Modification (PTM)

Any chemical alteration of a protein after translation, affecting its structure, localisation, or function.

Phosphorylation

Addition of a phosphate group to Ser, Thr, or Tyr residues by kinases, often regulating protein activity and signalling.

Glycosylation

Attachment of carbohydrate chains (N- or O-linked) to certain amino acids, influencing protein folding, stability, and trafficking.

Prenylation (Lipidation)

Covalent addition of isoprenyl lipid groups that anchor proteins to cellular membranes.

Prosthetic Group

A non-protein molecule (e.g., heme) covalently attached to a protein and essential for its biological activity.

Ubiquitination

Covalent linkage of the 76-amino-acid protein ubiquitin to lysine residues of target proteins, marking them for degradation.

Proteolysis

Specific cleavage of protein precursors to activate or inactivate them, e.g., conversion of angiotensinogen to angiotensin II.