Question

How many ATP equivalents (ATP -> ADP + Pi) are needed to make a 200 amino acid polypeptide from a mRNA template, amino acids and tRNA molecules. GTP -> GDP + Pi counts as one ATP equivalent and ATP -> AMP + 2 Pi counts as 2 equivalents.

Answer 1

In protein translation, there are total 5 steps

1. Aminoacid activation or tRNA charging- requires 2 ATP equivalent as 1 ATP is converted to AMP.

2. INITIATION - 1 GTP utilised so it is 1 ATP equivalent.

3. Elongation - 1 GTP for elongation

4. Translocation - 1 GTP

5. Termination - 1 GTP

The TOTAL energy is 4 ATP ENERGY EQUIVALENT for 1 peptide bond synthesis. Therefore for 200 amino acids the the number of peptide bond is 199. So the ATP EQUIVALENT WILL BE 4*199 = 796.

Note: If the tRNA CHARGING is considered then the energy equivalent for 200 amino acids is (2*200) + (199*4)

= 1196 ATP equivalents.