Question

Beta-galactosidase protein has 1024 amino acids. How many molecules of glucose should be consumed to produce just 1 molecule of the beta-galactosidase?

Ignore the cost of amino acid biosynthesis; assume complete oxidation of glucose to CO2

Answer 1

Hi,
The beta-galactosidase is synthesized from 1024 aminoacids. These individual amino acids are joined together by peptide bond by utlizing 2 ATP molecules for each pair of amino acids.
1024 amino acids = 1023 peptide bonds.
1 peptide bond = 2 ATP;
1023 peptide bond = 2*1023 = 2026 ATP.

1 complete ooxidation of glucose to CO2 = 32 ATP ( considering glycolysis, TCA and ETC).
To produce 2026 ATP,we need = 2026 / 32 = 63.31 glucose molecules.= 64 glucose molecules.

We have ignored the 2 ATP required to activate amino acids, 2 ATP required to carry out rrofreading and all the ATP required to synthesize amino acids.
Please note that the yield of ATP is given to range between 30-32 in some books, and 36 or 38 in some. I have followed the one from Lhninger biochemistry.