Biology

6.4 Translation

6.4.1 Explain how the structure of tRNA allows recognition by a tRNA-activating enzyme that binds a specific amino acid to tRNA, using ATP for energy.

Each amino acid has a specific tRNA activating enzyme that helps tRNA to combine with its complementary mRNA codon. The enzyme has a 3 part active site that recognizes three things:

Ð'* A specific amino acid

Ð'* ATP,

Ð'* A specific tRNA.

The enzyme attaches the amino acid to the 3' end of the tRNA. The amino acid attachment site is always the base CCA.

6.4.2 Outline the structure of ribosomes including protein and RNA composition, large and small subunits, two tRNA binding sites and mRNA binding sites.

Ð'* Two subunits, large and small

Ð'* Proteins and ribosomal RNA molecules form part of structure.

Ð'* Binding sites for tRNA on ribosome surface, two tRNA molecules can bind to the ribosome.

Ð'* There is a binding site for mRNA on the ribosome surface.

6.4.3 State that translation consists of intitiation, elongation, and termination.

6.4.4 State that translation occurs in a 5' to 3' direction.

Translation occurs in a 5' to 3' direction. The ribosome moves along the mRNA toward the 3' end. The start codon is nearer to the 5' end than the stop codon.

6.4.5 Explain the process of translation including ribosomes, polysomes, start codons, and stop codons.

Initiation

Ð'* When RNA reaches the cytoplasm, it attaches its 5' end to the small subunit of the ribosome. AUG is called the start codon because it initiates the translation process.

Ð'* The anticodon on one end of a tRNA molecule is complementary to a specific codon on the mRNA. The codon AUG bonds with a tRNA molecule holding the amino acid methionine (the initiator tRNA).

Ð'* The large ribosomal subunit has two tRNA binding sites: the P site and the A site.