translation

translation

process of taking mRNA and making a protein, occurs in cytoplasm usinf ribosomes. codons on mRNA are translated into amino acids by help with tRNA

3 stages of translation

initiation, elongation, termination

tRNA

have regions that base-pair with themselves, forming clover shape. contain anticodon sequence

anitcodon

complementary to mRNA to bring correct amino acid

aminoacylation

process of adding an amino acid to tRNA

aminoacyl-tRNA synthetase

enzymes that catalyze aminoacylation

wobble hypothesis

multiple codons can code for the same amino acid

ribosomes

2 parts: large subunit and small subunit. subunits are made of rRNA and ribosomal proteins

3 binding sites of ribosomes

A (aminoacyl), P (peptidyl), E (exit)

aminoacyl (A) site

for incoming tRNA containing next amino acid for protein

peptidyl (P) site

for tRNA carrying growing polypeptide chain

exit (E) site

where tRNAs leave the ribosome

initation

ribosome’s small subunit associates with mRNA, Met-tRNA scans mRNA to find start codon and is in P-site, large subunit binds and completes ribosome

elongation

mRNA codons read one at a time, second tRNA binds to A-site, amino acid in P site is cleaved from tRNA, peptide bond forms between amino acids in P and A site, ribosome moves along mRNA to next codon, extending polypeptide, tRNAs shift to next site

reading frame

mRNA codons are read one at a time by ribosomes

peptidyl transferase

forms a peptide bond between amino acids in P and A site

termination

A-site of ribosome reaches STOP codon, small proteins release polypeptide, subunits dissociate, mRNA is destroyed

release factors

proteins that release polypeptide bonds

polysome

multiple ribosomes can translate a single mRNA molecule at one time