Question

Combustion of glucose (C6H12O6) is the main source of energy for animal cells: C6H12O6(s)+ 6O2(g)→ 6CO2(g)+ 6H2O(l) =ΔGrxn37°C−2872.kJ One of the most important uses to which this energy is put is the assembly of proteins out of amino acid building blocks. The Gibbs free energy of formation of one peptide bond, joining one amino acid to another, is 21/kJmol. Suppose some cells are assembling a certain protein made of 17 amino acids. (Note that the number of peptide bonds in the protein will be one less than the number of amino acids.) Calculate the minimum mass of glucose that must be burned to assemble 650.μmol of this protein. Round your answer to 2 significant digits.

Answer 1

Given the free energy formation of one peptide bond is 21 kJ/mol

By 17 amini acids they can form 17-1 = 16 peptide bonds

So the energy required to form 16 peptide bonds = 16 x 21 kJ/mol = 336 kJ

So 1 mole of protein requires 336 kJ of energy

650 micromoles = 650 x10^-6 moles of protein requires  650 x10^-6 x336 kJ = 0.2184 kJ

C6H12O6(s)+ 6O2(g)→ 6CO2(g)+ 6H2O(l) =ΔGrxn37°C −2872.kJ

Molar mass (g/mol) 180

upon combustion of 1 mol=180 g of glucose it produces 2872 kJ of heat

For M g of glucose the heat produced is 0.2184 kJ

M = ( 0.2184*180) / 2872

= 0.014 g of glucose