Lecture Notes: Protein Synthesis

Overview

Protein Synthesis: Process of making proteins, involving two main steps:
- Transcription: Copying a gene from DNA to mRNA.
- Translation: Using mRNA to produce a protein.

DNA: Contains genetic material in the form of thousands of genes in a cell's nucleus.
- Each gene has a specific sequence of bases that code for amino acids to form proteins.
Ribosomes: Structures that read the DNA sequence to make proteins, located outside the nucleus.
mRNA: Messenger RNA, a copy of a single gene that can exit the nucleus to reach ribosomes.
- Differences from DNA:
  - Shorter because it is only a single gene long.
  - Single-stranded.
  - Contains uracil (U) instead of thymine (T).

Uncoiling DNA: DNA is normally coiled into a helix; for transcription, it is uncoiled to expose bases.
RNA Polymerase: Enzyme that binds to DNA and synthesizes mRNA.
- Complementary Base Pairing:
  - C on DNA pairs with G on mRNA.
  - G pairs with C.
  - T pairs with A.
  - A pairs with U (since mRNA has U instead of T).
Template Strand: The DNA strand used by RNA polymerase to make mRNA.
Result: mRNA strand that can exit the nucleus and head to ribosomes.

mRNA and Ribosome Binding: mRNA binds to ribosomes to start protein synthesis.
Codons: Triplets of bases on mRNA that code for specific amino acids.
- Example: AGU codes for serine, CCA codes for proline.
tRNA (Transfer RNA): Molecules that bring amino acids to the ribosome.
- Have an anticodon complementary to mRNA codons to ensure correct amino acid sequence.
Building Amino Acid Chain:
- tRNA binds to mRNA codon, brings the correct amino acid.
- Ribosome joins amino acids to form a chain.
- Ribosome moves along mRNA, repeating process until the protein is complete.
Conclusion: The amino acid chain folds into a functional protein.

Protein synthesis is essential for cellular function and organism development.
Understanding transcription and translation is critical for grasping genetic expression.

End of Lecture