Signal Transduction

Second Messengers

Small, non-protein molecules or ions that relay signals from cell-surface receptors to target molecules inside the cell.

Role of Second Messengers in Signal Transduction

Second messengers play key roles in the molecular events initiated by the binding of a signaling molecule to a receptor.

Steps in Signal Transduction

Reception, activation of intracellular pathways, and production of second messengers that facilitate the signaling cascade.

Cyclic AMP (cAMP)

A second messenger produced from ATP by the enzyme adenylyl cyclase, activating protein kinase A.

Calcium Ions (Ca²⁺)

Ions that are released in response to signals and activate various proteins, including calmodulin.

Inositol Triphosphate (IP₃)

A second messenger that increases calcium ion release within the cell.

Diacylglycerol (DAG)

A second messenger that activates protein kinase C.

Amplification of the Signal

The process by which one activated receptor triggers the production of multiple second messengers for a large cellular response.

Specificity of the Response

Different cell types may utilize different second messengers to achieve cell-specific responses.

What is the function of second messengers in a cell?

They amplify and transmit signals received from cell-surface receptors, regulating various processes.

What does cyclic AMP activate?

Cyclic AMP activates protein kinase A (PKA).

What is the initial step in signal transduction involving second messengers?

A ligand (first messenger) binds to a specific receptor on the cell surface.

How do second messengers contribute to cellular responses?

By amplifying the initial signal and facilitating a wide range of cellular activities.

What is the role of IP₃ in signal transduction?

IP₃ acts to increase calcium ion release from the endoplasmic reticulum.