BIOL 4150 Study Guide - Final Guide: Melanocortin 4 Receptor, Melanocortin 1 Receptor, Proopiomelanocortin

IP₃

cAMP

Insulin

Diacylglycerol

Bind to water soluble ligands

Activate second messengers

Regulate transcription in response to ligand binding

Are normally located on the plasma membrane

Phosphorylation of the RTK

Cytoplasmic proteins bind the phosphorylated RTK

Dimerization of the RTK

The RTK binds to DNA to regulate transcription

An intracellular receptor activates phospholipase C, which cleaves a membrane protein to form IP₃, which then activates the opening of an ER channel protein, which releases cyclic AMP into the cytoplasm, where it binds to an intracellular enzyme that carries out a response.

A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP₃, which binds to a calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries out a response.

An ion-channel receptor opens, allowing a steroid hormone to enter the cell; the steroid hormone then activates protein kinases that convert GTP to GDP, which binds to an intracellular enzyme that carries out a response.

A tyrosine-kinase receptor activates adenylyl cyclase, which activates phospholipase C, which converts ATP into cyclic AMP, which binds to an intracellular enzyme that carries out a response.

activation of an enzyme molecule

activation of a specific gene by a growth factor

Breakdown of many cAMP molecules

activation of 100 molecules by a single signal binding event

The G protein releases GDP and binds to GTP

The target protein (adenylyl cyclase) is inactive

The regulatory subunits of PKA (Protein Kinase A) are bound to the catalytic subunits

The appropriate G protein is bound to GDP

Receptor protein

Extracellular signal molecule

Intracellular signaling molecule

Cellular response

Effector protein

Adenylyl phosphatase

Adenylyl kinase

Adenylyl dehydrogenase

Adenylyl cyclase

It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

It would employ a transduction pathway directly from an external messenger.

It would be able to carry out reception and transduction but would not be able to respond to a signal.

Hormones do not last long enough in the bloodstream to stimulate a cellular response

Only cells that have a specific transcription factor gene will be able to respond to the signal

Only cells in the immediate vicinity of the cell sending the signal will respond

Only cells that have a receptor for the specific signal will be able to respond to it