The key difference between ionotropic and metabotropic receptors is that ionotropic receptors allow the binding of ionic ligands to them that opens up the ion channel. Meanwhile, metabotropic receptors allow the binding of chemical ligands to the receptors, initiating a cascade of reactions via linking with a G protein.
Signal transduction and membrane transport are important processes in biology. Both play a vital role in the regulation of metabolism in the system. Majority of the metabolic pathways and membrane transportation take place through receptors that bind with ligands, which can be either ionic ligands or chemical ligands.
CONTENTS
1. Overview and Key Difference
2. What are Ionotropic Receptors
3. What are Metabotropic Receptors
4. Similarities Between Ionotropic and Metabotropic Receptors
5. Side by Side Comparison – Ionotropic vs Metabotropic Receptors in Tabular Form
6. Summary
What are Ionotropic Receptors?
Ionotropic receptors, also called ion channels, are channel proteins that facilitate the transport of ions. Channel proteins open when ions bind to the receptors. In other words, the binding of ions to the receptors leads to the opening of ion channels.
Figure 01: Ionotropic Receptors
Ion channels do not remain in the closed or opened state all the time. But, they are generally in the closed state. The binding of the ions to the ionotropic receptors do not lead to the activation of secondary molecules. Therefore, the effect of the ionotropic receptor does not last for a long time. The reactions upon activation of the ionotropic receptors do not give rise to a cascading transduction mechanism. Moreover, ionotropic receptors play an important role in neurotransmission. Apart from that, these are important elements in the membrane transport mechanisms such as the sodium- hydrogen transporter and the potassium transporter.
What are Metabotropic Receptors?
Metabotropic receptor is a type of receptor involved in the signal transduction mechanisms via a secondary messenger binding the receptor. The metabotropic receptor is found on the surface of cells. The most inherent type of receptor for the metabotropic receptor is G protein-coupled receptors. Thus, metabotropic receptors consist of receptors like glutamate receptors, muscarinic acetylcholine receptors and the serotonin receptors. Most metabotropic receptors are neurotransmitter ligands.
Figure 02: Metabotropic Receptors
The mechanism of action of metabotropic receptors depends on ligand binding. Upon binding of the G protein-coupled receptor to a ligand, a cascade of reactions is initiated by activating many secondary molecules. The opening of metabotropic receptors takes a longer time as it involves the activation of many molecules. Hence, the stability of the effect of metabotropic receptors is also high and more widespread.
There are a variety of functions in metabotropic receptors. They can either open or close a channel or participate in neurotransmission in particular.
What are the Similarities Between Ionotropic and Metabotropic Receptors?
- Ionotropic and metabotropic receptors are two types of membrane receptors.
- Both are important in neurotransmission.
- These receptors bind to their specific ligands
- Hence, their specificity and sensitivity are high during the binding with the ligands.
What is the Difference Between Ionotropic and Metabotropic Receptors?
The key difference between ionotropic and metabotropic receptors is the type of ligand that binds to each receptor. Ionic ligands bind to ionotropic receptors while non-ionic ligands bind to metabotropic receptors. Upon binding, metabotropic receptors initiate a cascading reaction or a signal transduction mechanism. But, the ionotropic receptors will open an ion gated channel. So, this is another difference between ionotropic and metabotropic receptors. Due to these effects, the sustainability and the coverage of the effect also vary between the ionotropic and metabotropic receptors.
The below infographic summarizes the difference between ionotropic and metabotropic receptors.
Summary – Ionotropic vs Metabotropic Receptors
Ionotropic and metabotropic receptors are two types of receptors that function in membrane transport and signal transduction. Ionotropic receptors bind to ionic ligands such as K+, Na+, Cl–, and Ca2+. Metabotropic receptors bind with non-ionic ligands such as chemical receptors or G protein-coupled receptors. Upon binding, these receptors initiate a cascading reaction such as a signal transduction reaction. Both of these mechanisms play an important role in neurotransmission. However, ionotropic receptors work as channels that open and close while metabotropic receptors are not channels. Thus, this summarizes the difference between ionotropic and metabotropic receptors.
Reference:
1. Silbering, Ana Florencia, and Richard Benton. “Ionotropic and Metabotropic Mechanisms in Chemoreception: ‘Chance or Design’?” EMBO Reports, Nature Publishing Group, Mar. 2010, Available here.
Image Courtesy:
1. “Open and closed conformations of ion channels” By Efazzari – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “G protein” By Tpirojsi – Own work (Public Domain) via Commons Wikimedia