Question

Which of the choices are examples of coupled reactions? In water, sodium choloride (NaCl) dissociates into sodium and chloride ions. ATP hydrolysis drives lactose synthesis from glucose and galactose. ATP is hydrolyzed by water without the presence of enzymes. ATP synthesis is driven by a proton gradient formed in the mitochondria Sucrose hydrolysis by water results in glucose and fructose.

Answer 1

1) ATP hydrolysis drive lactose synthesis from glucose and galactose

2) ATP synthesis is driven by a proton gradient in the mitochondria

A coupled reaction is one where the energy released from one reaction is used to drive the another reaction.

ATP hydrolysis releases a lot of energy which is used to drive many reactions in nature.

However dissociation of NaCl, ATP and sucrose in water, although it does release energy, does not copies the reason with any other reaction. They are uncoupled reactions.

ATP synthesis in mitochondria is possible due to the protons from NADH and FADH2 which driven through the inner mitochondrial membrane to the intermembrane space. The increase in proton concentration makes them do down their gradient back into the matrix through the ATP synthesis enzyme F1F0 ATP synthase. This drives the synthesis of ADP + Pi to give ATP.

The energy released from ATP hydrolysis is used to make lactose from glucose and galactose.