Translation AHL

Topic 7.4

7.4.1: Charging tRNA molecules

Each tRNA molecule is recognized by a tRNA-activating enzyme which binds a specific amino acid to the tRNA using ATP for energy. The process is outlined below, it is worth to note the shape of the tRNA molecule and the presence of CCA at the 3' end of the molecule.

Charging tRNA molecules

Figure 7.4.2: The structure of ribosomes

Structure of a ribosome

7.4.3 & 7.4.4: Translation

Translation of the mature mRNA occurs on ribosomes and consists of initiation, elongation, translocation and termination. The process of translation occurs in the 5' to 3' direction. The structure of a ribosome is shown below. While studying the structure notes protein and RNA composition, the presence of large and small subunits, three tRNA binding sites and in mRNA binding site.

7.4.5:Dipeptide structure

7.4.6: Translation processes

Figure 1: Initiation

Initiation Translation

Figure 2: Elongation

Elongation Translation

Table 1: The process of Elongation

The step numbers in the table correspond to the blue numbers in Figure 6 shown above.

Step Description
1 Charged tRNA molecules are produced from uncharged tRNA molecules as outlined in Figure 1 shown above.
2 Next amino acid charged tRNA moves into the empty A-site on the ribosome through complementary base pairing of the anti-codon on tRNA anticodon on mRNA.
3 Peptide bond formed between amino acid on the A-site in the amino acid on the growing polypeptide on the P-site.
4 Growing polypeptide chain transferred to the A-site tRNA.
5 ATP used to move the ribosome along the mRNA in the 5' to 3' direction.
6 Opens up the A-site for the next charged tRNA.
7 Uncharged tRNA removed from the E-site.
8 Elongation proceeds until a stop codon is reached.


Termination Translation

7.4.7: Protein synthesis on ribosomes

Protein synthesis on ribosomes
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