Communication is an important method to share an emotion or thought with each other. Humans talk to each other for making a communication process. Other animals used some kinds of sound to communicate with each other. Cells in the body also need to communicate. But there is no other method to make a communication. They can’t ever talk or make a sound. But communication is needed also. Without making communication, there will be trouble secreting some chemicals from a certain cell. Those chemical is going to help another cell. So, without communication, the whole process on side of the human body will be stopped. So, they used to communicate with each other with the help of chemicals. Cell Receptor is one component in this case.
What Are Cell Receptors?
Cell receptors are the communication method of the cells. Chemicals are secreted from the other cells. Those chemicals are going to attach to the cell receptors. Cell receptors assume them as the chemical message. They start decoding the message. And based on the message, they perform certain acts. There is no specific location of the cell receptors. Sometimes they can be on the cell membrane. Sometimes they can be inside the cell. It has a different location for different cells. But most of the time, they are found on the cell membrane.
There are mainly two parts in the cell receptors. They are the Ligand Binding Domain & Effector Domain. Ligand Binding Domain is the part of the cell receptors where the ligands bind and activate the receptor. Ligands are the chemicals that are secreted from the other cells. There is not any specific location of the Ligand Binding Domain. It can be anywhere on the Cell Receptors. Another part is the Effector Domain. This domain works after binding with the Ligand. It performs some special operations for specific cell receptors. They are always inside the cells to perform the operations.
Types Of Cell Receptors
Cell receptors can be available at two positions. One is on the cell membrane. And another is inside the cell. Based on the locations, cell receptors are divided into two categories.
Cell Receptor Based on Location
- Cell-Surface Receptors: These are present on the surface of the cell membrane. Ligands bind with it outside of the cell.
- Internal Receptors: These receptors are present inside the cells. Ligands enter the cell & bind with it. These ligands can cross the plasma membrane easily.
Receptors that present on the cell surface or cell membrane. There are a large number of cell receptors in this category. They have their Ligand Biding Domain outside of the cell. On the other hand, the Effector Domain should be inside the cell for executing the proper task. The ligands that usually bind with this type of cell receptors have a large size. They are termed Hydrophilic. They have a large size to enter the inside of the cell.
Because of that, these receptors are located outside of the cell. So, that the ligands will easily bind with the receptors without creating any problems. As the Hydrophilic ligands can’t easily come inside the cell because they can’t cross the cell membrane. The peptide hormones are like this category. They need to bind with the receptors outside of the cell.
Receptors that are present inside the cell either in cytoplasm or nucleus. There is a very small amount of cell receptors from this category. As they are located inside of the cell, the Ligand Binding Domain & the Effector Domain both should be inside of the cell. For that purpose, the ligand should enter the cell membrane. The ligands which attach this type of receptor have very small sizes. They are termed Hydrophobic.
There is a very small amount of this category of ligands. So, the number of receptors is also lower than others. In this case, the ligand will cross the membrane of the cell. Then it will attach to the Ligand Binding Domain. After that, the Effector Domain will start working. Steroid hormones are this category of ligands. They are promptly entering the cell. And they attached to the cell.
Cell Receptor Based On Function
Based on the function of the receptors, scientists have divided them into mainly four categories. They are based on function. They have not divided by the location of the receptors. Based on the function, the four categories are:
- Ligand-Gated Ion Channels: These are the receptors when they bind with ligands they provide a channel to exchange the ion.
- G-Protein Coupled Receptors: These are the receptors that are activated when a ligand bind with the G-Protein. After that, it performs certain operations.
- Catalytic Receptors: These are the receptors that are responsible for the enzyme secretion or the secretion of different substances from the cell.
- Nuclear Receptors: These are the receptors which are work with the nucleus & help to develop the DNA.
Ligand Gated Ion Channels
These are the cell receptors that are at the cell membrane. These are the channel-like structure. Whenever there is a ligand attached to it. It will open its channel. Using this channel, ions will exchange there. As it is a cell surface receptor. So, its Ligand Binding Domain is on the outside of the cell. There the ligand will attach to it. It helps to move in or out of the Na+, K+, etc. These types of receptors are often found in Skeleton Muscles.
It has a heteromeric structure. This means, there are many structural subunits present. Each subunit has a Ligand Binding Domain. But there should be only one Effector Domain. That domain is going to be used inside the cell. Also, there is a transmembrane domain. Inside that domain, there are four transmembrane alpha domains. The acetylcholine receptor is one example. Here, the Acetylcholine chemical will bind with the receptor. As a result, the channel will be opened. And the ions will be exchanged there. This is found in the skeleton muscles.
G-Protein Coupled Receptors
These types of cell receptors are also present on the cell membrane. They are a large family of receptors. There is like no ligands are found that can’t able to bind with this type of receptor. This means, there is a wide range of ligands that bind with the G-Protein Coupled Receptors. It is made up of seven transmembrane alpha helices. As they are the receptors are located on the cell membrane, they have their ligand-binding domain at the outside of the cells. Also, this has its effector domain inside of the cell.
G-Proteins are special proteins. They are made up of heterotrimers. Heterotrimers means a special kind of trimer that is derived from different types of monomers. These heterotrimers are also made up of three subunits. They are Alpha, Beta & Gamma Subunits. This type of receptor is being used for creating a large number of hormones. Secretion of several hormones is triggered by the help of these receptors. After binding with any ligand, it starts working inside the cells. Sometimes, it often opens the channels to insert the ions into the cell.
These are also under the cell-surface receptor category. They are also found on the cell membrane. They are associated with enzymic function. There is a single membrane alpha helix structure inside of Catalytic Receptors Also, as they are located on the cell membrane, there will be the ligand binding domain on the outside of the cell. On the other hand, the effector domain will be inside the cell. They are used for the enzymic secretion from the cell.
Insulin receptors are in this category. It helps to phosphorylate or dephosphorylates proteins. This means sometimes, it helps to add the protein substances to the enzyme & sometimes the present protein substances will be cut down by this receptor. Whenever there is a ligand attached to it, it helps to dephosphorylate proteins. This means it will cut down the protein. Otherwise, it will allow the insertion of the protein into the substances.
This is only one kind of receptor that does not belong to the Cell-Surface Receptor category. It is from the internal receptor category. This means this receptor is found inside the cell. They are not present outside of the cells. Here, in this case, the Ligand Binding Domain & the Effector Domain both are inside the cell. In this case, the ligand needs to enter the cell to bind with it. After binding with it, it performs some tasks.
Nuclear Receptors are the receptors that can change their position. It first belongs to the Cytoplasm, after attaching it to the ligand, it starts moving toward the nucleus. After that, it enters the nucleus. Then it attaches to the DNA & starts developing the DNA inside of the cell. The Estrogen & Progesterone hormones are from this category.
Need Of Receptors
- Receptors are needed to communicate between the cells. There are no neurons are present in cells to make communication.
- Receptors are like dendrons. They accept different chemicals & based upon the chemicals, it helps to perform certain operations in the body.
- Cells are the smallest unit of the body. And cell receptors are the main functional unit of it. Cell receptors are needed to do small functional tasks in the body. Cell receptors are the building blocks of the body. Human body function depends upon their successful performance.
- Cell receptors are responsible for the growth of the immune system. Cell receptors act as the guide to mark a substance as a foreign element to the body.
- Cell receptors help to make the growth of the cell. It helps to accept certain signals in form of chemicals & further divide them.
Importance Of Cell Receptors
Cell Receptors are the most important for the human body. It helps to interact within the cells. Cell interactions are important in all aspects. From protecting the human body to the secretion of the substance, communication is must needed. The cell receptors help to communicate. Without the cell receptors, the cell can’t able to command other cells to do a particular action. In absence of that particular action, some serious trouble will occur to the body. Sometimes when a body is attacked with foreign elements, there is a need to destroy them. Cells use communication to inform the other cells to destroy them. So, from these views, cell communication is needed. And cell receptors help to communicate properly.
Functions Of Receptors
- For Growth Of A Cell: Cell receptors act as the tool that helps to make the growth of the cell. Whenever there is a need to have self-growth, the cells secrete a special chemical. That chemical gets attached to the receptors. This provides a signal to make a growth of the cells by division.
- In Immune System: Cell Receptors help to recognize the potential threat to the human body. Immune cells secrete chemicals to identify foreign substances. The chemical gets attached to the foreign elements. After getting bind with it, it starts sending a proper signal to the T Lymphocytes. Then T Cells recognize that foreign element & destroy it.
- For Hormonal Secretion: Hormones are a necessary element of the human body. But one gland can’t able to secrete all the hormones for the human body. Different glands secrete hormones for the development of the body. The hormonal secretion is completely executed with the help of cell receptors. Hormones act on specific substances. This also works with the help of cell receptors. The hormonal chemical gets attached to the specific cell & starts acting upon it.
- For Enzyme Secretion: As well as hormones, enzymes also act using the cell receptors. Enzymes are chemicals. They act upon certain substances. These enzymes bind with the cell receptors of that substances. And helps to decompose it to any further other substance. In this way, it is clear that cell receptors also help in human digestion in a large context.
- Other Functions: Along with the above functions, there are several functions of the cell receptors. They are responsible for the death of any cell. When a cell seems a threat to the body, it secretes the proper signal to destroy itself. Also, there are a lot of functions are executed by cell receptors. Simply, they are responsible for each communication between the cells.
FAQs on Cell Receptor
Question 1: What are the domains found inside the cell receptors?
There are two domains inside the cell receptors. They are the Ligand Binding Domain. And another is Effector Domain. The ligand binds with the Ligand Binding Domain & Effector Domain performs some operation inside of the cell.
Question 2: Can a steroid hormone able to bind with Cell-Surface Receptors?
No! As steroid hormones are small in size. They have the power to cross the cell membrane. So, they will not bind with the Cell-Surface Receptors. They will bind with Internal Receptors.
Question 3: Can a peptide hormone able to bind with Internal Receptors?
No! As peptide hormones are large. They don’t have the power to cross the cell membrane. So, they will bind with the Cell-Surface Receptors. They will not bind with Internal Receptors.
Question 4: Somatic Nervous System works with which type of receptors?
The Somatic Nervous System works with the Ligand Gated Ion Channels. As this nervous system secretes Acetylcholine from the synapsis. These are used for the opening channel that is guarded by the receptors. So, Somatic Nervous System works with Ligand Gated Ion Channels.
Question 5: What are Hydrophilic & Hydrophobic ligands?
They are the categories of ligands. If a ligand is large, they are Hydrophilic. So, they need to bind with the Cell-Surface Receptors. Those ligands which have a small size are termed Hydrophobic ligands. They bind with the Internal Receptors.
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