Which chemical class of hormones usually attaches to membrane receptors on target cells? What cellular events usually follow?

The chemical class of hormones that usually attaches to membrane receptors on target cells is the peptide or protein hormones.

The cellular events that usually follow the attachment of peptide hormones to membrane receptors are: 1. Hormone binding to the receptor: The peptide hormone binds to its specific membrane-bound receptor on the surface of the target cell. 2. Activation of the receptor: The binding of the hormone to the receptor leads to activation of the receptor, which often changes its shape or conformation. 3. Initiation of intracellular signaling: The activated receptor triggers a series of intracellular signaling events (also known as signal transduction pathways). A common pathway involves activation of an enzyme called adenylate cyclase, which converts ATP (adenosine triphosphate) into cAMP (cyclic adenosine monophosphate). 4. cAMP functions as a second messenger: cAMP, a second messenger, plays a vital role in transmitting signals from the hormone-receptor complex to the downstream targets within the cell. It usually does this by activating a group of enzymes known as protein kinases. 5. Activation of protein kinases: Protein kinases are responsible for phosphorylating (adding a phosphate group) to specific target proteins, which either activates or inhibits their function. These protein kinases can further activate or inhibit other enzymes, ion channels, and transcription factors. 6. Cellular response: The changes in target proteins due to phosphorylation lead to various cellular responses, such as gene expression, ion transport, and metabolic pathways. 7. Termination of the signal: The signal is terminated by the action of phosphodiesterases, which break down cAMP, and phosphatases, which remove the phosphate group from target proteins. These series of events help in regulating a variety of physiological processes in the target cell in response to peptide hormones.