Signal Transduction and Cell Signaling, Part 1

These flashcards cover key concepts related to signal transduction and cell signaling as outlined in the lecture notes.

Signal Transduction Pathways

Processes that convert extracellular signals into cellular responses.

Extracellular Signals

Molecules that activate receptors on the plasma membrane or cytosol of a cell.

Ligands

Signaling molecules also known as first messengers.

G Protein-Coupled Receptors (GPCRs)

Large family of cell surface receptors that respond to various external signals.

Trimeric G Proteins

Heterotrimeric proteins that consist of three different subunits (alpha, beta, and gamma) and transduce signals from GPCRs.

Adenylyl Cyclase

An effector enzyme that converts ATP into cyclic AMP (cAMP) upon activation by G proteins.

Second Messengers

Intracellular signaling molecules released by the activation of receptors to propagate signal transduction.

Kinase

An enzyme that catalyzes the transfer of phosphate groups from high-energy donor molecules, like ATP, to specific substrates.

Phosphatase

An enzyme that removes phosphate groups from proteins, thereby altering their function.

cAMP

Cyclic adenosine monophosphate, a second messenger involved in transmitting signals within cells.

Hydrophobic Signaling Molecules

Molecules that can diffuse through the plasma membrane and bind to intracellular receptors.

Hydrophilic Signaling Molecules

Molecules that cannot cross the plasma membrane and interact with extracellular receptors.

Feedback Regulation

A process where the output of a cellular response regulates the activity of the signaling pathways.

Desensitization

A process by which a receptor becomes less responsive to its ligand after prolonged exposure.

Autocrine Signaling

Signaling where cells respond to signaling molecules they secrete themselves.

Paracrine Signaling

Signaling where cells release signals that affect nearby target cells.

Endocrine Signaling

Long-distance signaling in which hormones are released into the bloodstream to affect distant cells.

GTPase Activating Proteins (GAPs)

Proteins that accelerate the hydrolysis of GTP to GDP, terminating G protein signaling.

Guanine Nucleotide Exchange Factors (GEFs)

Proteins that promote the exchange of GDP for GTP, activating G proteins.

Calcium Ions (Ca2+)

A versatile intracellular second messenger involved in diverse signaling pathways.

Nitric Oxide (NO)

A gas that acts as both an intracellular and extracellular messenger.

Structure of PKA (Protein Kinase A)

Consists of two catalytic and two regulatory subunits, activated by cAMP.

Amplification in Signaling

The process whereby one signaling molecule leads to a large cellular response.

cGMP

Cyclic guanosine monophosphate, a second messenger similar to cAMP.

Receptor Kinase Activation

The process by which receptor binding induces a conformational change, activating the kinase activity.

Intracellular Signaling Cascades

Waves of signaling that transmit information from the receptor to target proteins inside the cell.

Glycogen Phosphorylase

An enzyme involved in the breakdown of glycogen to glucose.

Glycogen Synthase

An enzyme that promotes the synthesis of glycogen from glucose.

Arrestin

A protein that binds to phosphorylated GPCRs, preventing further G protein activation.

Signal Termination Mechanisms

Strategies that ensure a cellular response is turned off, including receptor phosphorylation and ligand degradation.

G Protein Activation

The exchange of GDP for GTP, activating the G protein.

Cell Surface Receptors

Membrane proteins that bind signaling molecules and initiate intracellular signaling.

Diversity of G Protein-Coupled Receptors

The broad array of receptors that respond to different signals, influencing the specificity of cellular responses.