20. During the sodium-potassium pump:
a. ATP binds to the membrane protein,
energizing it to accept 3 intracellular sodium ions and then change shape, allowing
the 3 sodium ions to pass outside the membrane.
b. 2 extracellular potassium ions then
bind to the protein, and as the protein changes shape again, allows them to
pass into the intracellular environment of the cytoplasm.
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Slichter