Cell Signalling Vocabulary

Vocabulary flashcards covering key terms, signal molecules, receptors, and pathways in cell signalling from Class 17 lecture material.

Signal Transduction

The process whereby an incoming extracellular signal molecule is received by a target cell receptor and converted into intracellular signals that alter cell behavior.

Endocrine Signaling

A long-range signalling mechanism in which specialized endocrine cells secrete hormones into the bloodstream for transport to distant target cells throughout the body.

Paracrine Signaling

A short-range signalling mechanism in which signalling cells secrete local mediators into the extracellular fluid to act on neighboring target cells.

Neuronal Signaling

A signalling mechanism where electrical impulses travel down a neuron's axon, triggering the release of neurotransmitters across synaptic junctions to target cells.

Contact-dependent Signaling

A short-range signalling mechanism requiring direct cell-to-cell contact, where a membrane-bound signal molecule on one cell binds to a receptor protein on an adjacent target cell.

Autocrine Signaling

A form of signalling where a cell secretes extracellular signals into the local environment that bind to specific receptors located on its own surface.

Delta

A transmembrane signal protein present on prospective neurons and developing cell types that binds to Notch receptors on neighboring cells to induce lateral inhibition.

Notch

A cell-surface receptor protein on target epithelial cells that binds to the membrane-bound inhibitory signal protein Delta to control cell specialization.

Adrenaline (Epinephrine)

A hormone originating in the adrenal gland (derived from the amino acid tyrosine) that increases blood pressure, heart rate, and metabolism.

Cortisol

A steroid hormone originating in the adrenal gland (derived from cholesterol) that affects the metabolism of proteins, carbohydrates, and lipids in most tissues.

Estradiol

A steroid hormone originating in the ovary (derived from cholesterol) that induces and maintains secondary female sexual characteristics.

Insulin

A protein hormone produced by $\beta$ cells of the pancreas that stimulates glucose uptake, protein synthesis, and lipid synthesis in various cell types.

Testosterone

A steroid hormone originating in the testis (derived from cholesterol) that induces and maintains secondary male sexual characteristics.

Thyroid Hormone (Thyroxine)

A hormone originating in the thyroid gland (derived from the amino acid tyrosine) that stimulates metabolism in many cell types.

Epidermal Growth Factor (EGF)

A protein local mediator originating from various cells that stimulates epidermal and many other cell types to proliferate.

Platelet-derived Growth Factor (PDGF)

A protein local mediator produced by various cells, including blood platelets, that stimulates many cell types to proliferate.

Nerve Growth Factor (NGF)

A protein local mediator originating in various innervated tissues that promotes the survival of certain classes of neurons and the growth of their axons.

Histamine

A local mediator derived from the amino acid histidine and secreted by mast cells that causes blood vessels to dilate and become leaky during inflammation.

Nitric Oxide (NO)

A dissolved gas signal molecule produced by nerve cells and endothelial cells lining blood vessels that diffuses across membranes to relax smooth muscle cells and regulate nerve-cell activity.

Acetylcholine

A neurotransmitter derived from choline, released at nerve terminals, that acts as an excitatory signal at nerve-muscle synapses and induces cell-type specific responses such as decreased heart rate, secretion, or contraction.

$$\text{cAMP}$$

Cyclic AMP, a small intracellular messenger molecule whose concentration changes inside nerve cells in response to serotonin reception.

$$\text{cGMP}$$

Cyclic GMP, an intracellular secondary messenger molecule synthesized from GTP by guanylyl cyclase upon binding of nitric oxide.

$$\text{Nitric Oxide Synthase (NOS)}$$

An enzyme present in endothelial cells that synthesizes nitric oxide (NO) from the amino acid arginine.

Guanylyl Cyclase

An intracellular receptor enzyme activated directly by bound nitric oxide (NO) to convert GTP into cyclic GMP.

Steroid Hormones

Hydrophobic signalling molecules (including cortisol, estradiol, and testosterone) that cross the plasma membrane to bind intracellular nuclear receptors in the cytosol or nucleus.

Molecular Switches

Intracellular signalling proteins that flip between inactive and active states upon signal reception and remain active until switched off by another intracellular process.

Protein Kinase

An enzyme that transfers a phosphate group from ATP onto a target protein to toggle its molecular switch to an active or inactive state.

Protein Phosphatase

An enzyme that removes a phosphate group from a protein to reverse the action of a protein kinase and turn off the molecular switch.

Phosphorylation Cascade

A series of protein kinases in a signalling pathway where each kinase is activated by phosphorylation and subsequently phosphorylates the next kinase in line.

Trimeric GTP-binding Proteins (G Proteins)

A major class of switch proteins consisting of three subunits that cycle between an active state bound to GTP and an inactive state bound to GDP.

Guanine Nucleotide Exchange Factors (GEFs)

Regulatory proteins that activate monomeric GTP-binding proteins by promoting the exchange of GDP for GTP.

GTPase-activating Proteins (GAPs)

Regulatory proteins that inactivate GTP-binding proteins by stimulating their intrinsic GTPase activity to hydrolyze bound GTP to GDP.