Tell the function of Na+ K+ pump

Reading File

Finding Sources

Reading File

Loading Image

Here is a detailed breakdown of the Na+/K+ ATPase Pump functions, drawn from Guyton & Hall and Medical Physiology textbooks:

Na+/K+ Pump (Na+-K+ ATPase) - Functions

Structure

The pump is a transmembrane protein complex with two subunits:

Alpha (α) subunit (~100,000 molecular weight) - the functional unit
Beta (β) subunit (~55,000 molecular weight) - anchors the complex in the lipid membrane

The α subunit has:

3 binding sites for Na+ on the intracellular side
2 binding sites for K+ on the extracellular side
ATPase activity on its intracellular portion

Mechanism of Action

Figure: The Na+/K+ pump transports 3 Na+ out and 2 K+ in per cycle, hydrolyzing one ATP to ADP + Pi. (Guyton & Hall, Medical Physiology)

Per cycle:

3 Na+ ions bind inside the cell to the α subunit
2 K+ ions bind on the outside
1 ATP is cleaved to ADP + phosphate (Pi)
Released energy causes a conformational change
3 Na+ are extruded outside; 2 K+ are pumped inside

The pump cycles through 8 conformational states (E1 and E2 forms), and under extreme conditions can actually run in reverse to synthesize ATP.

Key Functions

1. Maintains Ion Concentration Gradients

The pump keeps intracellular Na+ low and intracellular K+ high relative to extracellular fluid (ECF). This is the only primary active transport mechanism for Na+ in animal cells. - Medical Physiology, Boron & Boulpaep

2. Establishes the Resting Membrane Potential

Because the pump is electrogenic (3 Na+ out vs 2 K+ in = net positive charge leaving the cell), it creates a negative electrical potential inside the cell. This is a basic requirement for nerve conduction and muscle signaling. - Guyton & Hall, p.72

3. Controls Cell Volume

Inside the cell, large negatively charged proteins attract cations (Na+, K+), which drives osmotic water entry. Without the pump, cells would swell and burst. The pump continuously expels more ions (net loss) than it brings in, which draws water out of the cell. If a cell begins to swell, the pump is automatically activated to restore normal volume. - Guyton & Hall, p.72

4. Drives Secondary Active Transport

Many other transporters (co-transporters, antiporters) depend on the Na+ gradient created by the pump. By maintaining low intracellular [Na+], the pump provides the "downhill" gradient that drives secondary transport of glucose, amino acids, and other solutes into cells. - Medical Physiology

5. Energy Demand

In metabolically active cells like neurons, 60-70% of the cell's total energy may be used just by the Na+/K+ pump. This reflects how critical maintaining these gradients is to normal cell function. - Guyton & Hall

Summary Table

Feature	Detail
Ions transported	3 Na+ out, 2 K+ in (per cycle)
Energy source	1 ATP hydrolyzed per cycle
Type	Primary active transport (P-type ATPase)
Electrogenic?	Yes (net 1+ charge moves outward per cycle)
Inhibitor	Ouabain, cardiac glycosides (e.g., digoxin)
Main functions	Ion gradients, membrane potential, cell volume, drives secondary transport

This is a shared conversation. Sign in to Orris to start your own chat.