Free Biology resources · VCE Units 3 & 4
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Describe the role of mRNA and tRNA in the process of translation. (3 marks)
1 mark: mRNA carries the genetic code (sequence of codons) from the nucleus to the ribosome / acts as the template read during translation. 1 mark: tRNA carries a specific amino acid and has an anticodon that is complementary to a codon on the mRNA. 1 mark: tRNA anticodons base-pair with mRNA codons at the ribosome so amino acids are added in the correct order to form the polypeptide. Total: 3 marks.
A signal peptide is found at the start of many newly synthesised polypeptides destined for secretion from the cell. Explain the function of this signal peptide and outline the path the protein follows from synthesis to secretion. (4 marks)
1 mark: the signal peptide directs the ribosome/polypeptide to the rough endoplasmic reticulum (RER), so the protein enters the endomembrane system. 1 mark: the protein is synthesised into / processed within the RER. 1 mark: vesicles transport the protein from the RER to the Golgi apparatus, where it is modified/packaged. 1 mark: the protein is packaged into a secretory vesicle that fuses with the plasma membrane, releasing the protein by exocytosis. Total: 4 marks.
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