cell signaling

Growth Factors

Examples of local regulators that stimulate nearby target cells to grow and divide

Paracrine Signaling

when molecules travel only short distantances

Synaptic Signaling

A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell

Endocrine Signaling

Signaling used for long distance communication. this communication tends to have a slower response and a longer lasting effect.

Reception

The target cell's detection of a signaling molecule coming from outside the cell; involves the binding of the signaling molecule to a receptor protein

Transduction

A step or series of steps that converts the signal to a form that can bring about a specific cellular response

Signal Transduction Pathway

A sequence of changes in a series of different molecules during transduction

Response

The transduced signal triggers a specific change in cellular activity

Ligand

A molecule that specifically binds to another molecule (based on complementary shape with the receptor); causes shape change in the receptor

Examples of Transmembrane Receptors

GPCRs and ligand-gated ion channels

G Protein

A protein that binds the energy-rich molecule GTP

Ligand-gated Ion Channel

A membrane receptor that has a region that can act as a "gate" for ions when the receptor assumes a certain shape

Testosterone

A steroid hormone that passes through the cell membrane and binds to a receptor within the cytoplasm and turns on specific genes that control male sex characteristics

Transcription Factor

Special proteins that control which genes are turned on (transcribed into mRNA) in a particular cell at a particular time

Protein Kinases

Enzymes involved in phosphorylation cascades that transfer phosphate groups from ATP to other proteins; addition of phosphates activates the protein

Second Messengers

Small, nonprotein water-soluble molecules or ions involved in a signaling pathway; examples include cAMP and calcium ions

cAMP

Cyclic AMP; a second messenger that is activated by adenylyl cyclase

Evolution of Cell Signaling

The same signaling mechanisms are found within a diverse set of species

Quorum Sensing

An example of cell communication and signaling in bacteria using chemicals called autoinducers (ligands)

Epinephrine

An example of a chemical messenger (ligand) that binds to a transmembrane receptor (GPCR) and signals the breakdown of glycogen into glucose

positive feedback loop

feedback loop that causes a system to change further in the same direction

negative feedback loop

feedback loop which returns a system to homeostasis

juxacrine

Signals target adjacent (touching cells)

paracrine

signals diffuse to and affect nearby cells

ligand

A molecule that binds specifically to a receptor site of another molecule.

autocrine

term for hormones that act on same cells that secrete them

cytoplasmic receptors

Receptors located inside the cell that bind to signals that can diffuse across the plasma membrane.

receptor

on or in a cell, a specific protein to whose shape fits that of a specific molecular messenger, such as a hormone

enzyme coupled receptors

Transmembrane protein that, when stimulated by the binding of a ligand, activates an intracellular enzyme (either a separate enzyme or part of the receptor itself).

kinase

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule.

phosphoralate

protein kinases (add phosphate)

phosphatases

remove phosphate groups