PROTEIN SYNTHESIS THE DETAILS TRANSLATION The Details Process

PROTEIN SYNTHESIS THE DETAILS

TRANSLATION: The Details Process that occurs after transcription. n Occurs in the cytoplasm, with the help of ribosomes and transfer RNA. n

n TRANSLATION: The Details Translation refers to putting something into a different language – the message on the m. RNA will be translated into a polypeptide chain

The Ribosome Consists of a large and small subunit. n 2 subunits bind to m. RNA clamping it between them. n

The Ribosome Moves along the m. RNA in the 5’ 3’ direction. n Ribosome reads triplets of bases from the m. RNA (codons) n

Fig 2 pg 250

Transfer RNA (t. RNA) delivers aa’s to a polypeptide building site (the ribosome) n Single stranded n looks like a clover leaf n Anticodon at one end recognizes m. RNA codon n

Transfer RNA (t. RNA) Opposite end of t. RNA carries the corresponding amino acid. n t. RNA recognizes m. RNA when complementary bases pair between the codon and anticodon n

Fig 3 pg 251

Transfer RNA (t. RNA) Question: What is the anticodon found on the t. RNA carrying tyrosine? n Question: What amino acid is found on the t. RNA with an anticodon of CAU? n

Every t. RNA carries one specific aa

TRANSLATION Steps INITIATION ELONGATION TERMINATION POST-TRANSLATIONAL MODIFICATION PROTEIN animation

TRANSLATION 1) n n n INITIATION m. RNA exits the nucleus after modifications and enters the cytoplasm. Ribosomes recognize 5’ cap & bind to m. RNA ribosome starts translating at the start codon AUG

TRANSLATION 1) n n INITIATION the start codon ensures that the correct reading frame is used by the ribosome AUG codes for methionine, therefore every pr- starts with the aa methionine

n ribosomes have 2 sites that bind t. RNA: n A (acceptor) site – where t. RNA brings in new aa n P (peptide) site – where peptide bonds form between aa’s in growing polypeptide

Pg 252 First t. RNA is brought into P site – carries Met because the start codon is AUG

Pg 252 - Elongation 2 nd t. RNA enters A site

Pg 252 A peptide bond forms between the 2 aa’s

Pg 252 Ribosome translocates one codon over. t. RNA brings in the appropriate aa into A site.

2) ELONGATION n t. RNA’s are released from the P site n t. RNA is recycled by aminoacylt. RNA synthetase which adds their corresponding aa to them

Elongation Diagram

3) TERMINATION n when the ribosome reaches one of 3 stop codons (UGA, UAA, or UAG) the 2 subunits disassociate. n there is no corresponding t. RNA for the stop codon

The process is repeated until the ribosome reaches a stop codon. Pg 252

3) TERMINATION n A pr- called a release factor recognizes the ribosome has stalled and helps the polypeptide chain release from the ribosome. n the polypeptide chain may be altered in the cytoplasm

2 ribosome subunits fall off m. RNA Pg 252

Termination Diagram

Translation: Simplified translation animation

OVERALL: In Detail

OVERALL: Less Detail