bio

Ligand

A signaling molecule that binds to a receptor.

Receptor

A protein on the cell surface or inside the cell that detects a ligand.

Signal Transduction Pathway

The series of steps that convert a signal on a cell’s surface to a cellular response.

Second Messenger

Small molecules (like cAMP, Ca²⁺, IP₃) that relay signals inside the cell.

Kinase

An enzyme that adds a phosphate group to a protein, often activating or deactivating it.

Phosphorylation

The addition of a phosphate group to a protein to change its activity.

PK (Protein Kinase)

A type of kinase that helps transmit signals in pathways.

PKB (Protein Kinase B / Akt)

A kinase activated by insulin that inhibits GSK3.

GSK3 (Glycogen Synthase Kinase 3)

A kinase that inhibits glycogen synthase when active.

Glycogen Synthase

Enzyme that builds glycogen from glucose.

Autocrine Signaling

When a cell signals to itself.

Paracrine Signaling

When a cell signals to nearby cells.

Endocrine Signaling

When a cell signals to distant cells via hormones in the blood.

Direct Contact / Juxtacrine Signaling

When cells signal through direct contact with each other.

Transcription Factor

A protein that turns genes on or off in response to a signal.

Hydrophilic Ligand

A ligand that cannot cross the membrane; binds to a membrane receptor.

Hydrophobic Ligand

A ligand that can cross the membrane; binds to an intracellular receptor.

Inhibition

When a molecule decreases the activity of another protein.

Activation

When a molecule increases the activity of another protein.

Feedback Regulation

When a pathway is controlled by its own output (positive or negative).