Question

Question 4 1 pts Which of the following correctly describes the Nat/K+-ATPase? O a. The ratio of Na+UK+ pumped in one cycle is 1:1. ob. It is electrogenic. O c. The pump is open to the cytosol in the E2 conformation. O d. It pumps faster in the presence of digitalis. Question 5 1 pts Which of the following best describes ATP synthase? O a. A pore for facilitated diffusion. O b. An escalator. c. A rotary motor. O d. A hydraulic lift.

Answer 1

Answer 4) The correct option is b (it is electrogenic).

Na⁺/K⁺ ATPase are also called as sodium pumps are a kind of electrogenic pumps. During Na⁺/K⁺ pumping, three sodium ions are transported out of the cell via ATPase while two K+ ions are imported from outside to inside of the cell. Thus, during this unequal transport, there is one net positive charge is exported out of the cell thereby causing the process to be electrogenic. Hence, this option is correct.

Option a is incorrect: Na⁺/K⁺ ATPase involves 3: 2 ratio. For every 3 sodium ions exported, 2 potassium ions are imported. Hence, this option is incorrect.

Option c is incorrect: During cytosolic opening of gate (of Sodium pump), the protein is in E1 conformation. Hence, this option is incorrect.

Option d is incorrect: Digitalis is an inhibitor of sodium pump. Hence, this option is incorrect.

Answer 5) The correct option is c (a rotary motor).

ATP synthase is a kind of rotary motor. It has two sub units: F0 and F1. F0 subunit is fixed in to the membrane however F1 subunits protrudes out of the membrane (inside the mitochondria). F1 subunit has a rotational potential and rotation brings conformational changes in ATP synthase which ultimately drives ATP synthesis.

Option a is incorrect: Facilitated diffusion is a kind of passive transport where spontaneous transport of molecules (or ions) takes place. ATP synthesis is not a spontaneous process. Hence, this option is incorrect.

Option b and d are incorrect: ATP synthase does not work on the principle of escalator or hydraulic lift. However, it 's function is based upon rotation mechanism. Hence, these options are incorrect.