Cell Communication

intercellular signaling

communication between cells

intracellular signaling

communication within a cell

ligand

molecule produced by a signaling cell that binds with a specific receptor, delivering a signal in the process

target cells

cell that has a receptor for a signal or ligand from a signaling cell

receptor

protein in or on a target cell that bind to ligands

categories of signaling

• paracrine signaling - a cell targets a nearby cell

• endocrine signaling - a cell targets a distant cell through the bloodstream

• autocrine signaling - a cell targets itself

• direct signaling across gap junctions - a cell targets a cell connected by gap junctions

paracrine signaling

• signals that act locally btwn close cells

• move w diffusion through extracellular matrix

• ex. synaptic signaling

endocrine signaling

• signals from distant cells

• typically slower response, more long-lasting effect

• ligands released = hormones

autocrine signaling

produced by signaling cells that can also bind to released ligand

direct signaling across gap junctions

diffusion of small molecules or ions between connected cells

internal receptors

found in the cytoplasm of the cell and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane

cell surface receptors

• cell-surface protein that transmits a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell

  • ex. ion channel linked receptors, G-protein linked receptors, enzyme-linked receptors

phosphorylation

One of the most common chemical modifications that occurs in signaling pathways

• the addition of a phosphate group to a molecule such as a protein

• the phosphate can be added to a nucleotide such as GMP to form GDP or GT

• transfer of phosphate catalyzed by an enzyme called kinase

dimer

chemical compound formed when two molecules join together

growth factor

ligand that binds to cell-surface receptors and stimulates cell growth