Stages of Protein Synthesis

Introduction

• Topic focused on protein synthesis for Triple Biology Higher Tier.
• Important because exam questions could be tricky.
• Previous knowledge: DNA is a double-stranded polymer of nucleotides with bases A, T, G, C.
• DNA strands are complementary: A pairs with T, C pairs with G.

DNA and Proteins

• Proteins are polymers of amino acids.
• Humans have 20 different amino acids.
• Order of amino acids determines protein shape and function.
  • Example: Enzymes like amylase or structural proteins like collagen.
• Order of amino acids in a protein is determined by gene's base sequence.

Protein Synthesis Process

• Two Stages: Transcription and Translation

• Stage 1: Transcription (Nucleus)

  • Base sequence of a gene is copied into a complementary template called messenger RNA (mRNA).
  • mRNA is single-stranded.
  • mRNA exits nucleus to cytoplasm.

• Stage 2: Translation (Cytoplasm)

  • mRNA attaches to a ribosome.
  • Amino acids are brought to ribosome by transfer RNA (tRNA).
  • Ribosome reads triplets of bases on mRNA to join amino acids in correct order.
  • Once complete, protein folds into its unique shape to perform its function.

Additional Resources

• Practice questions available in revision workbook linked above.

[Music]