5 Steps to a 5 AP Biology, 2014-2015 Edition

124 ❯ STEP 4. Review the Knowledge You Need to Score High

Large ribosomal subunit mRNA

A site

(b)

Small ribosomal subunit tRNA ♦To start, the P site lies over the AUG codon of the mRNA and

P site the tRNA carrying the appropriate amino acids binds to the site.

(a) The tRNA carrying the next amino acid arrives at the A site.

Random amino acids

(c)

(f)

(e)

♦This process continues until the stop codon is reached and the

protein is complete.

AUG CGG

♦A peptide bond forms between the two amino acids. The amino

acid from the P site hops onto the A site amino acid, freeing the

tRNA in the P site to leave and find another amino acid to carry.

(d)

Old P site

New P site New A site

Translocation: The ribosome slides along the mRNA in such a

way that the A site becomes the new P site, and the next tRNA

comes into the new A site carrying the next amino acid.

Figure 11.6 A pictorial representation of translation.