USABO 11: Cell Communication

Quorum sensing

Bacteria sensing the concentration of signaling molecules to monitor their own local cell density.

Biofilm

An aggregation of bacteria cells attached to a surface by molecules secreted by the cells after reaching a certain density.

Signal Transduction Pathway

The sequence of changes in a series of different molecules that converts a signal to a form that brings about a specific cellular response.

Paracrine signaling

A type of local signaling in animals where signaling molecules travel short distances to influence nearby cells.

Growth factors

A class of local regulators in animals that stimulate nearby target cells to grow and divide.

Synaptic signaling

A specialized type of local signaling in the nervous system involving an electric signal traveling along a nerve cell triggering neurotransmitter secretion.

Hormones

Molecules used by plants and animals for long distance signaling.

Endocrine signaling

Hormone signaling in animals, where specialized cells release hormones that travel through the circulatory system to reach target cells.

Signal Reception

The detection of a signaling molecule by a target cell when it binds to a receptor protein located at the cell's surface.

Ligands

Molecules that specifically bind to another molecule.

G Protein-Coupled Receptors (GPCRs)

The largest family of cell surface receptors that work with the help of G proteins.

Receptor Tyrosine Kinases

Membrane receptors that attach phosphate groups to tyrosines, triggering a transduction pathway.

Ligand-gated ion channel

A type of membrane channel receptor that opens or closes when a signaling molecule binds to it.

Intracellular receptors

Receptor proteins found in the cytoplasm or nucleus of target cells.

Transcription factors

Special proteins that control which genes are turned on.

Phosphorylation cascade

A signal transduction pathway where a series of different proteins are phosphorylated in turn.

Protein phosphatases

Enzymes that rapidly remove phosphate groups from proteins to turn off signal transduction pathways.

Secondary messengers

Small, water-soluble molecules or ions that are components of signal transduction pathways.

Cyclic AMP (cAMP)

A secondary messenger produced from ATP, broadcasting signals to the cytoplasm.

Adenylyl cyclase

An enzyme that converts ATP to cAMP in response to an extracellular signal.

Inositol triphosphate (IP3)

A secondary messenger that binds to an IP3 gated ion channel in the ER, triggering calcium influx.

Signal Amplification

The amplification of a signal during signal transduction as each step produces more activated products.

Scaffolding proteins

Large relay proteins that help speed up signal transfer by simultaneously attaching several relay proteins.

Apoptosis

Controlled cell suicide that occurs when cells are damaged or have reached the end of their life span.

Caspases

Enzymes that cut up proteins and DNA during apoptosis in mammals.