The key difference between ion channel and ion pump is that ions move passively through ion channels while ions move actively through ion pumps.
Ions travel across the plasma membrane through ion channels or ion pumps. Ion channels are transmembrane proteins that passively transport ions down their electrochemical gradient across the cell membranes. Ion pumps are transmembrane proteins that actively transport ions against a concentration or electrochemical gradient across the plasma membranes. Both ion channels and ion pumps are found in the cell membrane. They are selective for specific ions.
CONTENTS
1. Overview and Key Difference
2. What is an Ion Channel
3. What is an Ion Pump
4. Similarities Between Ion Channel and Ion Pump
5. Side by Side Comparison – Ion Channel vs Ion Pump in Tabular Form
6. Summary
What is an Ion Channel?
An ion channel is a specialized protein located in the cell membrane. Ion channels passively transport ions across the cell membrane along the concentration gradient. Structurally, ion channels are heteromultimeric complexes composed of one to four pore-forming α subunits arranged around a central membrane-spanning shaft. Generally, ion channels have a selectivity filter which allows only one type of ion to travel across. Therefore, most ion channels are selective for specific ions. However, some ion channels such as ligand-gated ion channels permit the passage of multiple ion species.
Figure 01: Ion Channel
Ion channels can be either non-gated or gated. Voltage-gated ion channels and ligand-gated ion channels are two types of gated ion channels. In fact, a majority of ion channels fall into these two broad categories: voltage-gated or ligand-gated. Na+, K+, Ca2+ and Cl− ions mostly move through ion channels. Ion channels affect the membrane potential since they generate an ionic current by the movement of charged ions through membrane channels.
What is an Ion Pump?
Ion pump is a transmembrane protein that actively transports ions across the cell membrane. Ion pumps use energy from ATP in order to generate gradients. Then the ions move against the concentration gradient through the ion pumps. Similar to ion channels, ion pumps are also selective for ions. Na+/K+ pumps, H+ pumps, Ca2 + pumps and Cl− pumps are several specific ion pumps.
Figure 02: Ion Pump
Ion pumps can also be categorized as primary or secondary active transporters based on the method they use to move ions. Primary active transporters hydrolyze ATP to produce energy in order to transport ions across the membrane. Secondary active transporters use electrochemical gradient created across the membrane by pumping ions in or out of the cell. Secondary active transporters can be either antiporters or symporters. Antiporters pump two different ions or solutes in opposite directions across the membrane. Symporters pump two different ions or solutes in the same direction.
What are the Similarities Between Ion Channel and Ion Pump?
- Ion channel and ion pump are two types of transmembrane proteins that facilitate the movement of ions across the membrane.
- They contribute to control the incessant traffic of ions across the membrane.
What is the Difference Between Ion Channel and Ion Pump?
Ion channels allow ions to passively flow down a concentration gradient across the membrane while ion pumps actively transport ions against a concentration gradient across the membrane. Thus, this is the key difference between ion channel and ion pump. Moreover, ion channels can be gated or non-gated while ion pumps have at least two gates.
The below infographic lists more differences between ion channel and ion pump in tabular for side by side comparison.
Summary – Ion Channel vs Ion Pump
Ion channel and ion pump are two types of proteins that transport ions across the cell membrane. Ion channels transport ions passively without the use of energy while the ion pumps transport ions actively with the use of energy. So, this is the key difference between ion channel and ion pump. Moreover, ion channel needs only a single gate while the ion pump needs at least two gates.
Reference:
1. Purves, Dale. “How Ionic Movements Produce Electrical Signals.” Neuroscience. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. “Ion Channel.” ScienceDirect Topics, Available here.
Image Courtesy:
1. “Ion channel” – Original uploader was Outslider (Paweł Tokarz) at pl.wikipedia – Transferred from pl.wikipedia to Commons by Masur using CommonsHelper. (Public Domain) via Commons Wikimedia
2. “Sodium-potassium pump and diffusion” By Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436.Derivative by Mikael Häggström – File:Blausen_0211_CellMembrane.png (CC BY 3.0) via Commons Wikimedia