Signal Transduction and Membrane Receptors

Vocabulary flashcards covering signal transduction concepts, receptor categories, receptor tyrosine kinase, amplifier enzymes, and G protein-coupled receptor pathways based on the lecture.

First Messenger

The extracellular signal molecule sent between cells (such as a hormone or neurotransmitter) that binds to a membrane receptor protein.

Second Messenger System

The intracellular signaling cascade inside the cell that is activated following signal transduction and ultimately alters target proteins to cause a cell response.

Receptor Channel

A type of membrane receptor where ligand binding opens or closes an ion channel, modulating the flux of ions and altering the cell's membrane potential.

Integrin Receptor

A category of membrane receptor where ligand binding alters the cytoskeleton, leading to changes in cell structure and shape.

Receptor Enzyme

A membrane receptor consisting of a receptor on the extracellular surface tethered to an enzyme on the intracellular surface of the cell membrane.

Signal Amplification

The process of broadcasting an intracellular signal where a single extracellular first messenger leads to the production of many intracellular second messengers.

Receptor Tyrosine Kinase

An example of a receptor enzyme that undergoes a conformational change upon extracellular ligand binding to activate its intracellular kinase, which phosphorylates tyrosine residues on target proteins.

Adenyl Cyclase

A membrane-bound amplifier enzyme that, when allosterically activated by a G protein, converts ATP into cyclic adenosine monophosphate ($\text{cAMP}$).

Guanyl Cyclase

An enzyme that converts guanosine triphosphate ($\text{GTP}$) into the potent intracellular second messenger cyclic guanosine monophosphate ($\text{cGMP}$).

Cyclic AMP (cAMP)

A potent intracellular second messenger synthesized from ATP by the amplifier enzyme adenyl cyclase.

G Protein-Coupled Receptor (GPCR)

A seven-transmembrane spanning receptor linked to an intracellular G protein that, upon ligand binding, releases the G protein to modulate amplifier enzymes or ion channels.

G Protein Inactive State

The conformation of a G protein when it is bound to guanosine diphosphate ($\text{GDP}$) and attached to its associated membrane receptor.

G Protein Active State

The state triggered by signal binding where the G protein swaps $\text{GDP}$ for guanosine triphosphate ($\text{GTP}$), physically dissociates from the receptor, and moves along the intracellular membrane surface.

Protein Kinase A (PKA)

An intracellular enzyme activated by cyclic AMP ($\text{cAMP}$) that phosphorylates target proteins through covalent modulation, altering cell structure and function.