Question

What is atp coupling?

Answer 1

`"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.