What is atp coupling?

1 Answer
Jun 25, 2015

#"ATP"# coupling is the use of the free energy released by the hydrolysis of #"ATP"# to drive a thermodynamically unfavourable reaction.

Explanation:

For example, the conversion of glucose to glucose-6-phosphate by the enzyme hexokinase is thermodynamically unfavourable, with #ΔG = "+14.3 kJ/mol"#.

The hydrolysis of #"ATP"# to #"ADP"# is a highly favourable process, with #ΔG = "-30.5 kJ/mol"#.

The reactions are

#"glucose " + cancel("P"_i) → "glucose-6-P" + cancel("H"_2"O")#; #ΔG = "+14.3 kJ/mol"#

#"ATP" + cancel("H"_2"O") → "ADP" + cancel("P"_i)#; #ΔG = "-30.5 kJ/mol"#

#bar("glucose " + "ATP" stackrel("hexokinase")(→) "glucose-6-P" + "ADP")#; #ΔG = "-16.2 kJ/mol"#

The coupled reaction has a negative free energy, so the process is thermodynamically favourable.