Translation and Protein Synthesis

Vocabulary flashcards covering the stages of translation, protein structure, and the nature of the genetic code.

Nuclear Pore Complex (NPC)

A gateway that controls transport between the nucleus and cytoplasm, acting as the docking point for mRNA export.

Amino Acids

Biological building blocks of proteins containing an amino group ($–NH_{2}$), a carboxyl group ($–COOH$), a hydrogen atom, and a variable R-group.

Peptide Bond

A covalent bond formed between the amino group of one amino acid and the carboxyl group of another via a condensation reaction.

Polypeptide Chain

A sequence of many amino acids linked together that can fold into a functional protein.

Primary Structure

The linear sequence of amino acids in a protein, which is determined directly by the DNA sequence.

Secondary Structure

Local folding of a polypeptide chain due to hydrogen bonding, resulting in shapes like the $\text{α-helix}$ or $\text{β-pleated sheet}$.

Tertiary Structure

The overall three-dimensional folding of a single polypeptide, stabilized by hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds.

Quaternary Structure

The association of two or more polypeptide chains, such as in the protein Haemoglobin.

Genetic Code

The set of rules used to translate nucleotide sequences in mRNA into amino acid sequences in proteins.

Triplet Code

A characteristic of the genetic code where three nucleotides form one codon specifying one amino acid.

Degenerate

A property of the genetic code where multiple codons can code for the same amino acid, such as $GAA$ and $GAG$ both coding for glutamate.

Universal

The principle that nearly all organisms use the same genetic code for protein synthesis.

Non-overlapping

A rule in the genetic code stating that each nucleotide belongs to only one codon.

Unambiguous

A characteristic of the genetic code where each individual codon specifies only one amino acid.

AUG

The start codon that codes for methionine and initiates the process of translation.

Stop Codons

The codons $UAA$, $UAG$, and $UGA$ which signal the end of translation.

tRNA (Transfer RNA)

An adaptor molecule approximately $74–95$ nucleotides long that carries specific amino acids to the ribosome.

Acceptor Arm

The part of the tRNA located at the $3′$ end that binds to a specific amino acid.

Anticodon Arm

The region of tRNA containing a three-base sequence that recognizes and pairs with complementary codons on mRNA.

40S Subunit

The small ribosomal subunit in eukaryotes, consisting of $18S$ rRNA and $33$ proteins.

60S Subunit

The large ribosomal subunit in eukaryotes, consisting of $5S$ rRNA, $5.8S$ rRNA, $28S$ rRNA, and $49$ proteins.

rRNA (Ribosomal RNA)

A structural and catalytic molecule that forms the framework of ribosomes and catalyzes peptide bond formation.

Translation Initiation

The stage of protein synthesis where the small ribosomal subunit, mRNA, and initiator tRNA carrying methionine assemble at the start codon.

P site

The ribosomal site where the initiator tRNA is positioned and where the growing peptide chain is held.

Elongation

The stage of translation where amino acids are added one by one through codon recognition, peptide bond formation, and translocation.

A site

The ribosomal site where a charged tRNA first arrives and its anticodon pairs with the mRNA codon.

Translocation

The step during elongation where the ribosome moves one codon along the mRNA in the $5′ \rightarrow 3′$ direction.

E site

The exit site where empty tRNA moves before being released from the ribosome.

Termination

The final stage of translation triggered by a stop codon, resulting in the binding of release factors and the release of the completed polypeptide.