mRNA and Protein Synthesis

Overview

• mRNA (messenger RNA): Carries genetic information from DNA out of the nucleus to ribosomes for protein production.

Ribosomes

• Eukaryotic cells can contain several million ribosomes.
• Function: Use mRNA to assemble amino acids into proteins essential for life.
• Structure: Composed of one large and one small subunit.

Process of Protein Synthesis

1. Assembly: Ribosome subunits assemble around mRNA.
2. mRNA Movement: mRNA passes through the ribosome.
3. Amino Acids: Carried by tRNA (transfer RNA) attached to amino acids.

Transfer RNA (tRNA)

• Role: Carries amino acids into the ribosome.
• Structure: Larger green molecules.
• Function: Matches codon on mRNA with anti-codon on tRNA.

Ribosome Sites

• A Site (Aminoacyl site): Entry point for tRNA carrying amino acids, checks codon-anti-codon match.
• P Site (Peptidyl site): Holds tRNA carrying the growing protein chain.
• E Site (Exit site): Releases spent tRNA after amino acid is added to the chain.

Translation Process

• Codon Reading: mRNA read in groups of three letters (codons).
• tRNA Matching: Each codon on mRNA matches anti-codon on tRNA.
• Amino Acid Assembly: Larger ribosome subunit removes amino acid from tRNA, adds to protein chain.
• Ratcheting: mRNA moves through ribosome, advancing by one codon.

Protein Folding

• Protein chain emerges from ribosome, folding into specific shapes based on amino acid sequence.

Central Dogma

• Describes the process of turning the four-letter DNA code into proteins, the building blocks of life.