Lecture Notes: Crash Course Biology with Dr. Sammy

Introduction

• Cells build billions of peptides (baby proteins) continuously.
• Proteins are essential for building cells, chemical reactions, and oxygen transport.
• There are over 10,000 unique proteins in the human body.
• The process of turning messages into proteins is called translation.

DNA and mRNA

• DNA: Contains life's instructions, housed in the cell nucleus.
• mRNA: Messenger RNA that copies DNA instructions and exits the nucleus.
• mRNA uses nucleotides: Adenine (A), Uracil (U), Cytosine (C), and Guanine (G).
• mRNA's structure is similar to DNA but uses Uracil instead of Thymine.

Translation Process

• Proteins are made from amino acids, different from mRNA's nucleotides.
• Translation: The conversion of mRNA into proteins via codons (three-letter words).
  • Codons correspond to specific amino acids (e.g., G-U-A for valine).
  • Stop codons signal the end of a sequence.
• Ribosome: Cellular machine translating mRNA into proteins.
  • Composed of protein and ribosomal RNA (rRNA).
  • Operates like an assembly line.

Steps of Translation

1. Initiation
   • Small ribosome part binds to mRNA starting at start codon (AUG for methionine).
   • tRNA (transfer RNA) brings amino acids to ribosome.
   • Complementary nucleotide pairing with mRNA.
2. Elongation
   • Ribosome reads mRNA codons; tRNAs bring more amino acids.
   • Limited to holding three tRNAs at once.
   • Fast-paced assembly to continue building peptides.
3. Termination
   • Stops at stop codons, releasing amino acid chain.
   • Peptides grow into proteins through folding and combining with polypeptides.

Importance of Proteins

• Proteins are essential for activities like playing sports and creating content.
• Universality of codons hints at a common ancestor for all life.
• Cells rapidly build peptides, faster than current lab methods.

Advances in Protein Science

• Evolution has optimized peptide synthesis in cells.
• mRNA technology has been developed over decades for medical applications.
  • Dr. Katalin Karikó's work pivotal in mRNA vaccine development for COVID-19.
  • mRNA vaccines instruct cells to produce viral proteins for immune response.

Conclusion

• Recognition of proteins’ roles in diverse processes like blood function and immune responses.
• Future potential for mRNA in treating other diseases.
• Upcoming episodes will explore gene expression.

Additional Resources

• Visit BioInteractive.org/CrashCourse for educational materials.
• Support Crash Course on Patreon to keep it free for everyone.