The enyme hexokinase catalyzes the phosphorylation of glucose as the first step

Question

The enyme hexokinase catalyzes the phosphorylation of glucose as the first step of glycolysis and is an example of a coupled reaction. What is the ?G°' for the phophorylation of glucose to glucose-6-P by hexokinase? Circle the correct answer.

(a) -44.3 kJ/mol

(b) -16.7 kJ/mol

(c) 0.0 kJ/mol

(d) +16.7 kJ/mol

(e) +44.3 kJ/mol

To answer questions 1-4, consult these values for hydrolysis of phosphorylated compounds phosphoenolpyruvate (PEP) pyruvate P 61.9 kJ/mol -30.5 kJ/mol ATP ADP Pi -13.8 kJ/mol glucose-6-phosphate glucose Pi -43.1 kJ/mol creatine phosphate-creatine Pi -9.7 kJ/mol glycerol 3-phosphate glycerol P 1,3-bisphosphoglycerate 3-phosphoglycerate Pi -49.0 kJ/mol

Explanation / Answer

Answer is (B)

D-glucose + ATP D-glucose-6-phosphate + ADP ------- Go = -16.7

Its an a coupled reaction and the reaction can be made into two reactions.

The sum of the two reactions results in an overall negative free energy change, the strongly spontaneous hydrolysis of ATP is coupled to the otherwise unspontaneous glucose phosphorylation.

D-glucose + phosphate D-glucose-6-phosphate + H2O ----- Go = +14.3

ATP + H2O ADP + phosphate -------- Go = -31.0

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