BIO 1305 Chapter 11: Cell Communication

Ligand

A signaling molecule.

Receptor protein

Molecule to which the receptor binds.

Signal tranduction

Converts the information in the signal into a cellular response; results from the binding of the ligand and the receptor.

Quorum sensing

Process by which bacteria sense local population density with the concentration of signaling molecules.

Signal tranduction pathway

A series of steps that result from the binding of a mating factor at the cell surface.

Direct contact

Type of local signaling where the cells are essentially touching with cell junctions.

Paracrine signaling

Type of local signaling where the cells secrete messenger molecules that travel only short distances.

Synaptic signaling

Type of local signaling that occurs in the neurons.

Synapse

Association of neuron and target cell.

Endocrine signaling

Type of long-distance signaling that releases hormones that travel to target cells via the circulatory system.

Signal reception

The first stage of cell signaling where the target cell detects a signaling molecule that binds to a receptor protein.

Signal transduction

The second stage of cell signaling where the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway.

Cellular response

The third stage of cell signaling where the transduced signal triggers a specific response in the target cell.

plasma membrane proteins

Most signal receptors are ______________________.

G protein-coupled receptors (GPCRs)

Cell-surface transmembrane receptors that work with the help of a G protein.

G proteins

Proteins that bind the energy-rich GTP.

Receptor tyrosine kinases (RTKs)

Membrane receptors that catalyze the transfer of phosphate groups from ATP to another protein.

Ligand-gated ion channels

Receptor acts as a gate that opens and closes when the receptor changes shape. Allows sodium and calcium atoms to pass through.

Intracellular receptor proteins

Found in the cytoplasm or nucleus of target cells.

Activated hormone-receptor complex

Can act as a transcription factor, turning on or off specific genes.

Protein kinases

Transfer phosphates from ATP to protein in a process called phosphorylation.

phosphorylation cascade

Many relay molecules in signal transduction pathways are protein kinases, creating a _____________________________.

Protein phosphatases

Rapidly remove the phosphates from proteins in a process called dephosphorylation.

Second messengers

Small, non-protein, water-soluble molecules or ions that spread throughout a cell by diffusion.

Cyclic AMP and calcium ions

Common second messengers.

Cyclic AMP (cAMP)

A small molecule produced from ATP, is one of the most widely used second messengers.

Adenylyl cyclase

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

regulation

Ultimately, a signal transduction pathway leads to _________________ of one or more cellular activities.

genes

Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by turning ________ on or off in the nucleus.

Enzyme cascades

Amplify the cell's response to the signal.

Scaffolding proteins

Large relay proteins to which several other relay proteins are attached.

Inactivation mechanisms

An essential aspect of cell signaling. If the concentration of external signaling molecules falls, fewer receptors will be bound.

programmed cell death

Cells that are infected, damaged, or at the end of their functional lives often undergo _____________________________.

Apoptosis

The best understood type of programmed cell death, which prevents enzymes from leaking out of a dying cell and damaging neighbouring cells.