Exam 4 Cell Signaling

BIO 221

Cell communication

The process by which cells detect and respond to signals from their environment or other cells.

Environmental signaling

Communication that allows cells to respond to changes like temperature nutrients toxins or light.

Intercellular communication

Communication between cells to coordinate activities like growth immune responses and tissue function.

Cell membrane receptors

Proteins on the cell surface that bind signaling molecules and initiate a cellular response.

Signaling molecules (ligands)

Chemical messengers that bind to receptors to trigger signaling.

Signal transduction pathway

A series of intracellular steps that convert an external signal into a specific cellular response.

Cellular response

The result of signaling such as gene expression enzyme activation or cell division.

Yeast glucose response

A pathway where yeast detect glucose and activate metabolism-related processes.

Direct intercellular signaling

Communication through physical connections between cells.

Connexons

Channel proteins in animal cells that form gap junctions.

Innexons

Channel proteins in invertebrates similar to connexons.

Plasmodesmata

Channels between plant cells that allow direct communication.

Contact-dependent signaling

Communication requiring direct cell contact where the ligand is attached to the signaling cell.

Autocrine signaling

A cell signals itself.

Paracrine signaling

Signals affect nearby cells.

Endocrine signaling

Hormones travel through the bloodstream to distant cells.

Receptor activation

Occurs when a ligand binds to a receptor activating it.

Extracellular domain

Part of receptor that binds the ligand.

Cytoplasmic domain

Part of receptor that initiates internal signaling.

Signal transduction

Process where a receptor activation triggers intracellular signaling pathways.

Intracellular targets

Molecules inside the cell affected by signaling such as proteins enzymes or transcription factors.

Enzyme-linked receptor

A receptor that activates an enzyme when a ligand binds.

Kinase

Enzyme that adds phosphate groups to proteins.

Phosphatase

Enzyme that removes phosphate groups from proteins.

Phosphorylation cascade

A chain reaction where kinases activate multiple proteins.

Ligand

A molecule that binds to a receptor.

Ligand-gated ion channel

A channel that opens or closes when a ligand binds allowing ions to pass.

G protein-coupled receptor (GPCR)

A receptor that activates a G-protein when a ligand binds.

G-protein

A protein that binds GDP or GTP and transmits signals inside the cell.

GDP

Inactive form of G-protein.

GTP

Active form of G-protein.

Intracellular receptor

A receptor located inside the cell in the cytoplasm or nucleus.

Nuclear receptor domains

Ligand-binding DNA-binding and activation domains.

Hydrophobic signaling molecules

Molecules that can diffuse through the cell membrane such as steroid hormones.

Receptor activation (intracellular)

Ligand binding enables receptor to regulate gene expression.

Receptor dimerization

Two receptors join together after ligand binding.

Ras G-protein

A small GTP-binding protein involved in signaling pathways.

Ras activation

Occurs when GDP is replaced with GTP.

Signal cascade

A sequence of protein activations transmitting a signal.

Signal inactivation

Turning off signaling via phosphatases or GTP hydrolysis.

Transcription factors

Proteins that regulate gene expression.

Gene expression

Process of producing proteins from DNA.

Second messenger

Small molecules that amplify signals inside the cell.

cAMP

A second messenger made from ATP.

AMP

Inactive form after cAMP is broken down.

Adenylyl cyclase

Enzyme that converts ATP into cAMP.

Protein Kinase A (PKA)

Enzyme activated by cAMP that phosphorylates proteins.

GPCR cAMP pathway

Ligand binds GPCR activates G-protein activates adenylyl cyclase produces cAMP.

Epinephrine

Hormone that triggers energy release.

PKA enzyme regulation

Activates glycogen breakdown enzymes and inhibits glycogen synthesis enzymes.

Cellular response to epinephrine

Increased glucose availability for energy.

Signal amplification

A process where one signal leads to many downstream effects producing a large response.