Cell Communication & Signaling – Vocabulary Flashcards

Vocabulary flashcards covering key terms and concepts from the Cell Communication & Signaling lecture.

Homeostasis

The maintenance of a stable internal environment in spite of external changes, achieved through cellular sensing and responses to signals.

Stimulus

Any internal or external change that triggers a cellular response via signaling pathways.

Signal (Ligand)

A molecule released locally or at a distance that binds a receptor on a target cell to initiate signal transduction.

Receptor

A protein molecule (extracellular or intracellular) that specifically binds a ligand and initiates a cellular response.

Target Cell

The cell that possesses the specific receptor required to bind a signaling molecule and respond.

Membrane-Bound Receptor

A receptor located on the plasma membrane that binds extracellular ligands and triggers intracellular signaling cascades.

Intracellular Receptor

A receptor located in the cytoplasm or nucleus that binds ligands able to cross the plasma membrane (e.g., steroid hormones).

Gap Junction

A direct membrane connection allowing ions and small molecules to pass between adjacent cells for rapid signaling.

Paracrine Signaling

Local chemical communication in which a cell secretes a signal that affects neighboring cells.

Autocrine Signaling

Local signaling in which a cell releases a ligand that binds receptors on the same cell, regulating its own activity.

Hormonal (Endocrine) Signaling

Long-range communication in which hormones travel through the bloodstream to reach any cell with the appropriate receptor.

Neurotransmitter Signaling

Local chemical communication where a neuron releases neurotransmitters across a synapse to a specific target cell.

Signal Transduction

The molecular cascade that converts an extracellular signal into a specific intracellular response.

Ligand-Gated Ion Channel

A receptor that is also an ion channel; ligand binding opens the channel to allow ion flow.

Catalytic Receptor

A receptor that functions as an enzyme, catalyzing a reaction upon ligand binding.

G-Protein Coupled Receptor (GPCR)

A membrane receptor that activates heterotrimeric G-proteins, initiating downstream signaling cascades.

Signal Amplification

The process by which a single ligand-receptor event triggers activation of many downstream molecules, producing a large cellular response.

First Messenger

The extracellular signaling molecule (ligand) that binds to a receptor to start signal transduction.

Second Messenger

An intracellular signaling molecule generated or released in response to receptor activation (e.g., cAMP, Ca²⁺).

Adenylyl Cyclase

The enzyme activated by certain G-proteins that converts ATP to the second messenger cAMP.

cAMP (Cyclic AMP)

A second messenger that activates protein kinases, leading to phosphorylation of target proteins.

Protein Kinase

An enzyme that transfers phosphate groups to proteins, modifying their activity during signaling pathways.

Phospholipase C (PLC)

A G-protein–activated enzyme that converts membrane phospholipid DAG into IP₃ during signaling.

IP₃ (Inositol 1,4,5-trisphosphate)

A second messenger produced by PLC that triggers release of Ca²⁺ from intracellular stores.

Calmodulin

A Ca²⁺-binding protein activated by increased cytosolic Ca²⁺; it modulates activity of various target proteins.

Steroid Hormone Signaling (Direct Gene Activation)

A signaling mechanism in which a steroid hormone enters the cell, binds an intracellular receptor, forms a hormone-receptor complex that binds DNA, and directly alters gene transcription.