LOG IN Get Started

Translation

Laura Armstrong

Teacher

Laura Armstrong

Contents

What is Translation?

 ↓

Step-by-Step Process of Translation

 ↓

Protein Folding (Formation of Secondary & Tertiary Structure)

 ↓

Recall Questions

This topic requires prior knowledge of transcription. You can test your knowledge on this below.

What is the role of RNA polymerase in transcription?

RNA polymerase joins RNA nucleotides together via phosphodiester bonds in condensation reactions.

What is splicing, and why does it only occur in eukaryotic cells?

  • Splicing removes introns (non-coding regions) from pre-mRNA, leaving only exons to form mature mRNA.
  • It only occurs in eukaryotic cells because prokaryotic genes do not contain introns.

How does mRNA leave the nucleus after transcription?

Mature mRNA exits the nucleus via a nuclear pore and enters the cytoplasm, where it attaches to a ribosome for translation.

Topic Explainer Video

Check out this @LauraDoesBiology video that explains translation or read the full notes below. Once you've gone through the whole note, try out the practice questions!

What is Translation?

Translation is the second stage of protein synthesis, where the mRNA sequence is used to assemble a polypeptide at the ribosome. It involves mRNA, ribosomes, tRNA, and amino acids.

Step-by-Step Process of Translation

Remember, the sequence of bases on the mRNA determines the sequence of amino acids in the polypeptide.

mRNA Binds to the Ribosome

  • The mRNA molecule attaches to a ribosome.
  • The ribosome reads the mRNA codons (triplets of bases) one at a time.

tRNA Delivers Amino Acids

  • Transfer RNA (tRNA) molecules, each carrying a specific amino acid, bind to the ribosome.
  • The anticodon on the tRNA will bind to a complementary codon on the mRNA.

Peptide Bond Formation

  • The ribosome catalyses the formation of a peptide bond between adjacent amino acids, forming a polypeptide chain.
  • This requires energy from ATP.
  • The first tRNA detaches, and the ribosome moves to the next codon.

Process Repeats Until a Stop Codon is Reached

  • This continues until the ribosome reaches a stop codon (UAA, UAG, UGA) on the mRNA.
  • The ribosome releases the completed polypeptide chain.

What Happens to the Polypeptide After Translation?

Once translation is complete and the polypeptide chain is released, it undergoes further modifications to become a fully functional protein. 

Protein Folding (Formation of Secondary & Tertiary Structure)

  • The polypeptide folds into a specific 3D shape, which is crucial for its function.
  • Different types of bonds form between amino acids, including: 
    • Hydrogen bonds (hold α-helices and β-pleated sheets in place).
    • Ionic bonds (between positively and negatively charged R-groups).
    • Disulfide bridges (strong covalent bonds between sulphur atoms where the amino acid cysteine is present).
  • The final shape determines whether the protein is: 
    • Globular (e.g., enzymes, haemoglobin).
    • Fibrous (e.g., collagen, keratin). 

Key Players in Translation

Component  Function
mRNA Carries the genetic code from DNA to the ribosome.
Ribosome The site where translation occurs.
tRNA Carries specific amino acids to the ribosome.
Amino Acids The building blocks of proteins.
Peptide Bonds Join amino acids together to form a polypeptide chain.
Start Codon (AUG) Signals the beginning of translation (codes for methionine).
Stop Codon (UAA, UAG, UGA) Signals the end of translation, the polypeptide will be released from the ribosome when a stop codon is reached.

Key Terms 

  • Translation: The process of assembling a polypeptide chain based on the mRNA sequence at the ribosome.
  • Codon: A sequence of three bases on mRNA that codes for an amino acid.
  • Anticodon:  A complementary three-base sequence on tRNA that binds to an mRNA codon.
  • tRNA (Transfer RNA): Carries specific amino acids to the ribosome for translation.
  • Peptide Bond: A covalent bond that joins amino acids together in a polypeptide.
  • Stop Codon: A codon that ends translation, releasing the protein.
No answer provided.

Exam Tips

Always mention the role of tRNA in Translation – remembering they each carry a specific amino acid.

If asked about translation steps, make sure to explain codon-anticodon pairing and peptide bond formation clearly.

Know the difference between transcription and translation – transcription occurs in the nucleus, translation occurs in the cytoplasm.

No answer provided.

Describe the process of translation in protein synthesis. (6 marks)

  1. mRNA attaches to a ribosome
  2. A tRNA molecule with a complementary anticodon binds to the mRNA codon
  3. The tRNA carries a specific amino acid. 
  4. The ribosome catalyses peptide bond formation between amino acids, forming a polypeptide chain. 
  5. This peptide bond formation requires ATP. 
  6. The ribosome moves along the mRNA, allowing more tRNA molecules to bring amino acids in the correct sequence. 
  7. The sequence of bases on the mRNA determines the sequence of amino acids in the polypeptide.
  8. The process continues until a stop codon is reached, and the polypeptide chain is released. 

Practice Question 1

Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!

Practice Question 2

If you want to try out another one, check this video out and see how you do!

Transcription