Pharmacology: Receptors and Receptor-Effector Systems

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Questions and Answers

What is the primary function of a receptor?

To synthesize neurotransmitters

To bind to ligands and initiate effects (correct)

To act as an enzyme

To regulate autacoids

What is the role of a transducer in a receptor-effector system?

To convey signals to cellular targets (correct)

To bind to ligands

To act as an enzyme

To synthesize neurotransmitters

What is the term used to describe the process of receptors acting as biochemical signal amplifiers?

Ligand binding

Catalysis (correct)

Signal transduction

Message propagation

What is the purpose of a receptor's ligand-binding domain?

To bind to agonists Signup and view all the answers

What is the result of a single ligand molecule binding to a receptor that is an ion channel?

Many ions flow through the channel Signup and view all the answers

What is the role of receptors in integrating extracellular information?

To coordinate signals from multiple ligands and metabolic activities Signup and view all the answers

What is the primary function of an effector protein?

To propagate biochemical effects Signup and view all the answers

What is the term used to describe the molecules that are synthesized or released by effector proteins?

Second messengers Signup and view all the answers

What is the ability of a drug to combine with a receptor to form a drug-receptor complex?

Affinity Signup and view all the answers

What type of antagonism occurs when an antagonist binds reversibly to a receptor, and its inhibitory effects can be overcome by increasing the dose of the agonist?

Competitive antagonism Signup and view all the answers

What is the term for the ability of a drug to initiate a biological response?

Intrinsic activity Signup and view all the answers

What is the main difference between competitive and non-competitive antagonism?

Reversible vs. irreversible binding Signup and view all the answers

What type of receptors are frequently plasma membrane-bound protein kinases?

Receptors for peptide hormones Signup and view all the answers

What is the term for a drug that possesses both affinity and intrinsic activity?

Agonist Signup and view all the answers

What happens to the dose-response curve in competitive antagonism?

A rightward shift occurs Signup and view all the answers

What is the result of increasing the dose of an agonist in non-competitive antagonism?

The maximum response is decreased Signup and view all the answers

Study Notes

Receptor

A receptor is a cellular macromolecule that binds to a drug to initiate its effects.
Important drug receptors are cellular proteins that normally function as receptors for endogenous regulatory ligands, such as hormones, growth factors, neurotransmitters, and autacoids.
A receptor has two main functions: ligand binding and message propagation.
A receptor contains a ligand-binding domain and an effector domain to deliver these functions.

Receptor-Effector System

A receptor, its cellular targets, and any intermediary molecules are referred to as a receptor-effector system or signal transduction pathway.
Effector proteins may not be the ultimate cellular component affected, but may synthesize or release another signaling molecule, known as a second messenger.

Properties of Physiological Receptors

Receptors act as integrators of extracellular information, coordinating signals from multiple ligands with each other and with metabolic activities of the cell.
Physiological receptors act catalytically, amplifying biochemical signals.
Even if a receptor is not an enzyme itself, it is still a formal catalyst.

Agonist

An agonist is a drug that combines with a receptor, possessing both affinity and efficacy.
Affinity is the ability of a drug to combine with a receptor, and efficacy is the ability to initiate an effect.

Antagonist

An antagonist is a drug that possesses only affinity, with no intrinsic activity.
Antagonists prevent the effect of an agonist but do not produce any effect of their own.
There are two types of antagonism: competitive and non-competitive.

Competitive Antagonism

In competitive antagonism, the antagonist binds reversibly to the receptor, and its inhibitory effects can be overcome by increasing the dose of the agonist.
Maximum response can be obtained, and a rightward shift occurs in dose-response curves.

Non-Competitive Antagonism

In non-competitive antagonism, the binding of the antagonist is irreversible or non-specific, and the antagonist cannot be overcome by increasing the dose of the agonist.
The slope of the curve is changed, and the maximum response is decreased on increasing the dose of the antagonist.

Classification of Receptors

One classification of receptors is as enzymes or receptor protein kinases.
Receptors for peptide hormones that regulate growth, differentiation, and development are frequently plasma membrane-bound protein kinases that act by phosphorylating target proteins.

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Description

Learn about receptors, their functions, and their role in pharmacology, including ligand binding and message propagation. Understand the receptor-effector system and its importance in cellular responses.