Question

How do most motor proteins ensure their movements are unidirectional? O Choose one: O A. They couple a conformational change to the formation of an ATP molecule from ADP and Pi. O B. Their asymmetrical structures support movement in only one direction. O C. They couple a conformational change to a thermodynamically unfavorable reaction. O D. They couple a conformational change to the hydrolysis of an ATP molecule. O E. They hydrolyze their bound GTP, effectively preventing movement in the reverse direction. O

Answer 1

Option D is correct.

Movement of most motor proteins is like mainly depends on the hydrolysis of ATP molecule.ATP inside cell is storage form of energy most biochemical reactions make use of. So hydrolysis of ATP releases stored form of energy, this energy being used by many biochemical processes to go on. Same mechanism happens with the motor proteins movement.

Motor proteins ensure their unidirectional movement by this process involving ATP hydrolysis.

Example movement of kinesin dimers over microtubules involves following steps

Kinesin heads when not bound to the microtubules are ADP bound, when comes in contact with microtubules releases its ADP in exchange for ATP in the cellular environment. This ATP bound head causes conformational change in the neck region of the kinesin compelling other head to bind to the microtubule, therefore releasing its bound ADP and exchanges for ATP. The previously bound head ATP is hydrolysed loosing its affinity for microtubule and head is released ready for another ATP, therefore maintaining the direction as the later bound head is still attached to the microtubule.

Option A is wrong as formation of ATP is energy rather energy storage process.

Option C is wrong, as thermodynamics remain same throughout the reaction as the cellular environment remain same.

The other options are not correct according to the question and the explained answer.