Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 3 - Section 3.3 - Membrane Transport - Before You Go On - Page 98: 19

Answer

The Na+-K+ pump is a primary active transport. 3 Na+ ions are pumped from the ICF into the ECF in exchange for 2 K+ ion being pumped from the ECS into the ICF. The Na+-K+ pump maintains a steep Na+ gradient that allows for secondary active transport to occur. The Na+-K+ pump also helps regulate cell volume, maintain membrane potential, and produce heat to keep the cells warm.

Work Step by Step

The Na+-K+ pump is basically a pump bailing out a leaky boat. The pump exchanges 3 Na+ for 2 K+ ions at the cost of 1 ATP. This keeps the K+ concentration higher and the Na+ concentration lower in the cell than in the ECF. Because the Na+ concentration is lower in the cell than in the ECF, sodium-glucose transporters can easily transport down the Na+ gradient into the cell. Therefore, the Na+-K+ facilitates secondary active transport. The Na+-K+ pump also helps regulate cell volume. The retention of these ions would cause osmotic swelling and lyse the cell. By actively pumping a net of one additional ion out of the cell, the intracellular ion concentration is reduced and the cell’s osmolarity is controlled.
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