Protein Synthesis Overview

Introduction

• Geared towards the Irish Leaving Certificate.
• Basic summary of protein synthesis.

Key Concepts

• Genes: Sections of DNA that code for proteins.
• DNA: Located in the nucleus of eukaryotic cells.
• Proteins: Made in ribosomes in the cytoplasm.

Problem in Protein Synthesis

• DNA cannot exit the nucleus due to its size.
• Solution: Gene code is copied onto a single-stranded molecule (mRNA) to move to ribosomes.

Stages of Protein Synthesis

• Remembered by the phrase: "I talk to people."

1. Initiation

• DNA unwinds at the gene.
• Enzymes break strands to expose bases.

2. Transcription

• Messenger RNA (mRNA) is created using DNA as a template.
• mRNA is single-stranded and complementary to DNA.
• RNA polymerase connects mRNA nucleotides.
• DNA Bases: A, T, G, C; RNA Bases: A, U, G, C (U replaces T).
• mRNA organizes bases into codons:
  • Codons: Groups of three bases
  • Types: Start codons, amino acid codons, stop codons

3. Translation

• mRNA travels to ribosomes.
• Ribosomes made of ribosomal RNA, composed of two subunits.
• Transfer RNA (tRNA): Carries amino acids to ribosomes.
• tRNA anticodons pair with mRNA codons, ensuring correct amino acid sequence.
• Peptide bonds form between amino acids.
• Process continues until a stop codon is reached.

4. Protein Folding

• Amino acid chain folds into a functional protein shape.
• Critical for protein function.

Additional Notes

• Some textbooks may consolidate stages differently.
• These notes are supplementary to textbooks.
• Practice with past exam papers is recommended.

Conclusion

• Four stages: Initiation, Transcription, Translation, Protein Folding.
• Videos are educational, not commercial.
• Best of luck in your studies!