Protein Synthesis: The process of making proteins.
Involves two main steps: Transcription and Translation.
Key Concepts
Transcription: Copying a single gene of DNA into mRNA (messenger RNA).
Translation: Using mRNA to produce a protein.
Importance of DNA
DNA is located in the nucleus and contains all genetic material.
Contains thousands of genes, each coding for specific amino acid sequences.
The sequence of bases in DNA determines the protein produced.
Structure of mRNA
Similar to DNA, but with key differences:
Single-stranded (DNA is double-stranded).
Contains Uracil (U) instead of Thymine (T).
Shorter than DNA (only one gene long).
Transcription Process
RNA Polymerase binds to DNA before the gene starts.
DNA strands separate, exposing bases.
RNA Polymerase reads DNA bases and synthesizes mRNA:
Base pairing rules:
A (adenine) pairs with U (uracil)
T (thymine) pairs with A
C (cytosine) pairs with G (guanine)
G (guanine) pairs with C
Once mRNA strand is complete, RNA Polymerase detaches, and DNA strands rejoin.
The mRNA strand exits the nucleus to reach the ribosome.
Translation Process
Ribosome binds to the mRNA to begin protein synthesis.
tRNA (transfer RNA) molecules bring amino acids to the ribosome:
Each tRNA has an anticodon at the bottom that is complementary to the mRNA codon.
Anticodon ensures the correct amino acid is added.
Amino Acids: 20 different types, each coded by specific triplet codons.
Example: Agu (codes for serine), CCA (codes for proline).
Steps in Translation
mRNA and ribosome bind together.
tRNA brings the amino acid to the ribosome according to the complementary codon.
Ribosome joins amino acids together, forming a chain.
The process repeats until a complete chain is formed.
The completed amino acid chain detaches and folds into a protein.
Conclusion
The processes of transcription and translation are crucial for protein synthesis, enabling cells to produce necessary proteins based on genetic information.