Receptors: definition, meaning, Functions, Types, Topics
Receptors are specialised proteins located on or inside cells that detect chemical, physical, and sensory stimuli. They convert external signals—like hormones, neurotransmitters, and environmental cues—into meaningful cellular responses. This guide covers the types of receptors, their functions, intracellular vs cell-surface receptors, examples, diagrams, and NEET-oriented MCQs.
This Story also Contains
- What Are Receptors?
- Classification of Receptors
- Function of Receptors
- Intracellular Receptors
- Cell Surface Receptors
- Receptors NEET MCQs (With Answers & Explanations)
- Recommended Video on Receptors
What Are Receptors?
Receptors are highly specialised proteins found either on or inside the cells that change conformation upon specific molecule binding. They form an integral part of physiological processes and mediate interactions between the cell and its environment.
Receptors are proteins that participate in detecting signals, among them hormones, neurotransmitters, and sensory stimuli, and acting accordingly. They allow the cell to respond to the changes and thus maintain homeostasis; they participate in growth, immune responses, and sensing.
Classification of Receptors
Receptors can be classified in several ways. Knowing the classifications is associated with the functions and mechanisms connected with the different kinds of receptors.
Based on Location
| Receptors | Description |
|---|---|
Cell Surface Receptors |
|
Intracellular Receptors |
|
Based on Function
| Receptors | Description |
|---|---|
Sensory Receptors |
|
Neurotransmitter Receptors |
|
Hormone receptors |
|
Function of Receptors
Protein molecules called receptors that are present in the target cell or on its surface perform a number of tasks, such as:
It controls the binding of cells.
It facilitates the transmission of signals.
It regulates the channels in the membrane.
Additionally, it has a role in immunotherapy and immunological responses.
Cell metabolisms such as growth, division, and death are induced by it.
Intracellular Receptors
The internal receptors include-
Growth Factor Receptors
Growth factor receptors are crucial for controlling the division, differentiation, and growth of cells. Among the receptors are:
Vascular endothelial growth factor (VEGF), neurotrophin, fibroblast growth factor (FGF), epidermal growth factor (EGF), insulin-like growth factor receptors and platelet-derived growth factor (PDGF) receptors
Cytokine Receptors
Through their ability to react to signals produced by other organelles, cytokine receptors let cells connect with the extracellular environment. Additionally, it plays a role in cell cycle modifications, mediator release, gene expression, etc.
Cell Surface Receptors
The cell surface receptors include-
B Cell Receptors (BCRs)
Also known as B cells or B lymphocytes. They circulate in the blood and lymph after being formed in the bone marrow.
B cell's primary job is to make antibodies that defend the body from invaders or foreign substances.
These cells are essential for both the start of allergic reactions and adaptive immunity.
T Cell Receptors (TCRs)
One type of lymphocyte that is produced in the thymus gland is the T cell.
They are in charge of clearing the body of infections.
Granulocyte Receptors
Receptors NEET MCQs (With Answers & Explanations)
Important questions asked in NEET from this topic are:
Classification of receptors
Intracellular and cell surface receptors
Practice Questions for NEET
Q1. What are receptors?
Proteins that bind to ligands and initiate a response
Proteins that transport ligands across cell membranes
Proteins that break down ligands into smaller molecules
Proteins that store ligands inside cells
Correct answer: 1) Proteins that bind to ligands and initiate a response
Explanation:
Receptors are proteins that are located on the surface of cells or inside cells. They are responsible for recognizing and binding to specific ligands, such as hormones, neurotransmitters, or drugs. When a ligand binds to a receptor, it can initiate a cellular response, such as a change in gene expression or the opening of ion channels.
Hence, the correct answer is option 1) Proteins that bind to ligands and initiate a response.
Q2. Receptors that respond to cold are called
Caloreceptors
Frigido Receptors
Baroreceptors
Tangoreceptors
Correct answer: 2) Frigido Receptors
Explanation:
Receptors that are sensitive to cold temperatures are classified as thermoreceptors, precisely, cold receptors or frigid receptors. These temperature-sensitive structures are situated in the skin and various other bodily tissues. Their primary function is to perceive temperature variations, which is essential for the organism's ability to sense and adapt to changes in its surroundings. Cold receptors are particularly significant in the detection of cold stimuli, contributing substantially to the maintenance of homeostasis by modulating body temperature. Their activation leads to vital physiological responses such as the initiation of shivering and the propensity to seek warmth, thereby illustrating their indispensable role in thermoregulation.
Hence, the correct answer is option 2) Frigido Receptors.
Q3. Assertion: Tendon and joint receptors provide information on the location and motion of various body parts.
Reason: Noci-receptors are the names given to them.
Both Assertion (A) and Reason (R) are the true and Reason (R) is a correct explanation of Assertion (A).
Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).
Assertion (A) is true and Reason (R) is false.
Assertion (A) is false and Reason (R) is true.
Correct answer: 3) Assertion (A) is true and Reason (R) is false.
Explanation:
The assertion is correct in stating that tendon and joint receptors provide information about the location and motion of various body parts. These receptors are types of sensory receptors that are found in muscles, tendons, and joints, and they provide information about the position, movement, and tension of these body parts. This information is crucial for maintaining balance, coordinating movement, and controlling posture.
However, the reason is incorrect. Nociceptors, also known as pain receptors, are a completely different type of sensory receptor that is responsible for detecting tissue damage and sending signals to the brain that result in the sensation of pain. Nociceptors are not the same as tendon and joint receptors, which provide information about the location and motion of body parts, not pain. In summary, the assertion is correct, but the reason is incorrect. Tendon and joint receptors provide information on the location and motion of various body parts, while nociceptors are pain receptors that detect tissue damage and send signals to the brain resulting in the sensation of pain.
Hence, the correct answer is option 3) Assertion (A) is true and Reason (R) is false.
Also Read:
Recommended Video on Receptors
Frequently Asked Questions (FAQs)
The hormone receptors bind its specific hormone and initiate signal transduction pathways, which then mediate growth, metabolism, reproduction, and many other physiological processes.
Receptors detect and respond to a wide range of signals, allowing cells and hence activities to communicate and coordinate in homeostasis maintenance and physiological process regulation.
GPCRs are associated with extra-cellular ligands. The latter triggers associated intra-cellular G proteins. In turn, the latter initiates the execution of downstream signalling pathways and consequent cellular responses.
Cell-surface receptors stay in the plasma membrane and act through signal molecules outside the cell. In contrast to the intracellular receptors, which are centrally located in the cell, they act through molecules that diffuse freely across the membrane.
Sensory receptors detect environmental stimuli and convert them into electrical impulses interpreted by the nervous system to mediate the perception of touch, temperature, light, sound, and chemicals.