Receptors are protein molecules found in cell membranes that bind to specific ligands. There are two main types of receptors: internal receptors located in the cytoplasm and nucleus, and cell surface receptors located in the cell membrane. Cell surface receptors are further divided into ion channel-linked receptors, G-protein coupled receptors, and enzyme-linked receptors. Receptors play an important role in cell signaling and activation by controlling ion flux, carrying signals, and serving as working sites for ligands.

1. Ravi Kumar
M. Pharma (Pharmacology)2nd Year
Bharat Institute of Technology
Meerut

2. Contents
 Introduction
 Types
 Structure
 Function

3. Introduction-
A receptor is a protein that present on/in cell
membrane, which binds to a specific molecule. The
molecule it binds is also known as ligand.
Or
Receptors are special structures that can be found
in cell membrane that receive a chemical signal. The
receptors are made of protein molecules such
as glycoprotein.

4. Ligand that’s bind with a receptor protein – Drug
substrates, inhibitors, activators, signaling lipids, and
neurotransmitters etc.

5. Types-
Receptors are mainly two types-
1. Internal Receptor
2. Cell Surface Receptors
1. Internal Receptor(Nuclear receptor)- The
internal receptors is know as intra-cellular or
cytoplasmic receptors because it’s also found in
cytoplasm.

6. When a ligand bind with a internal receptor it form a
complex of ligand-receptor. These complex are moves
into the nucleus and bind with a specific region of
DNA and enhance the production of mRNA.

7. 2. Cell Surface Receptors- It is also known as
transmembrane receptor protein that found on
the cell membrane.
Ligand that interact with cell surface receptors
do not have to enter into the cell.

8. There are further sub-divided into three main types-
• Ion channel-linked receptors
• G-protein receptors
• Enzyme-linked receptors
1. Ion channel-linked receptors- When a ligand
bind with this receptors after binding, start
conformational changes in the protein structure
that allows ions (Sodium, Calcium, Magnesium,
Hydrogen etc.) entry into the cell.

10. 2. G-protein receptors- It activate membrane
protein after binding a ligand.
The activated G-protein interact with ion channel
or an enzyme.
When a G-protein bind with a receptors, start
changing in the shape, become active and divided
into two different subunits.
Both subunits may be able to activate other
proteins.

12. 3. Enzyme-linked receptors- The enzyme-linked
receptors are cell surface receptors with intracellular
domain that associated with an enzyme.
When a ligand bind to the extracellular domain, a
signal is transferred through the membrane and
activating the enzyme. Due to this activation, produce
a response of ligand.

14. Function-
 It is responsible for cell signaling.
 It is responsible for cell activation.
 It control the ions flux across the cell membrane.
 It act as a carrier for signals.
 It act as a working site of a ligand.