Cell Signaling Fundamentals

A collection of vocabulary flashcards defining key enzymes, molecules, and stages involved in cellular signaling and transduction pathways based on the lecture notes.

Adenylyl cyclase

An enzyme in the cell membrane that converts $ATP$ into cyclic $AMP$ ($cAMP$) when activated (often by a G protein).

Cyclic AMP (cAMP)

A small intracellular signaling molecule made from $ATP$; it acts as a second messenger to relay and amplify signals inside the cell.

G protein

A signal-transducing protein that binds $GTP$/$GDP$; when activated, it can turn on/off enzymes or ion channels inside the cell.

G-protein-linked receptor (GPCR)

A membrane receptor that, when a ligand binds, activates a G protein on the inside of the membrane.

Hormone

A long-distance chemical signal (common in endocrine signaling) that travels through blood or body fluids to target cells.

Ligand

Any signaling molecule that specifically binds to a receptor (could be a hormone, neurotransmitter, local regulator, etc.).

Ligand-gated ion channel

A membrane receptor that opens or closes an ion channel when a ligand binds, changing ion flow and the cell’s electrical state.

Local regulator

A signaling molecule that acts over short distances (paracrine signaling), like growth factors or nitric oxide.

Protein kinase

An enzyme that adds a phosphate group to a protein (phosphorylation), usually changing that protein’s activity in a signaling pathway.

Protein phosphatase

An enzyme that removes a phosphate group from a protein (dephosphorylation), often turning off or resetting signals.

Reception

The first stage of cell signaling—when a target cell’s receptor detects/binds the signal (ligand).

Response

The final stage—what the cell actually does because of the signal (e.g., turn on a gene, change enzyme activity, open a channel, divide, move).

Second messenger

A small molecule/ion inside the cell that carries the signal onward after receptor activation (common examples: $cAMP$, $Ca^{2+}$).

Signal transduction pathway

The chain of molecular steps that converts a signal received at the cell surface (or inside the cell) into a specific cellular response—often a cascade of protein shape changes/phosphorylations.

Transduction

The “middle” stage of signaling—converting the receptor activation into intracellular messages and relay steps (often involving second messengers and kinase cascades).