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Multiple Choice
Which of the following shows the correct order of steps for the mechanism of the sodium-potassium ATPase? I. 2 K+ Ions bind. II. Phosphorylation of an Asp residue. III. Conformational change releasing 3 Na+ ions outside the cell. IV. 3 Na+ ions bind. V. Release of the phosphate group. VI. Conformational change releasing 2 K+ ions inside the cell.
A
II, I, V, III, IV, VI.
B
IV, II, III, I, V, VI.
C
I, II, III, IV, V, VI.
D
IV, II, I, III, V, VI.
E
IV, III, I, II, VI, V.
Verified step by step guidance
1
Understand the function of sodium-potassium ATPase: It is an enzyme that pumps sodium (Na+) out of cells and potassium (K+) into cells, using energy from ATP hydrolysis.
Identify the initial step: The process begins with the binding of 3 Na+ ions from the cytoplasm to the enzyme.
Next, ATP is used to phosphorylate the enzyme, specifically at an aspartate residue, which causes a conformational change.
This conformational change releases the 3 Na+ ions outside the cell and allows 2 K+ ions to bind from the extracellular space.
Finally, the phosphate group is released, causing another conformational change that releases the 2 K+ ions inside the cell, resetting the enzyme to its original state.