Cell Communication

A chemical signal that binds to a receptor protein, triggering the cell signaling process

Signaling process when a cell releases a ligand that binds to a receptor on the same cell, starting the cell signaling process. In autocrine signaling, the ligand-releasing cell and the target cell are the same cell. Examples of autocrine signaling include cancer cells, which release growth factors that stimulate the growth of their own cells

Signaling process where the ligand-releasing cell is in direct contact with the target cell that possesses the receptor for the ligand. Examples of juxtacrine signaling include the interaction between an antigen presenting cell and a helper T cell in the immune system

Signaling process where the ligand-releasing cell releases a ligand that has an effect on target cells that are near to the ligand-releasing cell. An example of paracrine signaling is synaptic signaling between neurons

Signaling process where the ligand-releasing cell releases a ligand that travels long distances to target cells. An example of endocrine signaling is the effect of insulin on target cells far from the pancreatic cells that released the insulin

Proteins embedded in the cell membrane that receive signals from ligands outside the cell. When cell membrane receptors bind to extracellular ligands, a shape change occurs in the cell membrane receptors, which starts the cell signaling process. Cell membrane receptors typically bind to hydrophillic ligands that cannot cross the cell membrane

Ligands involved in cell signaling that travel long distances from the ligand-releasing cell to the target cell

The process by which a cell responds to a ligand through a series of chemical reactions inside the cell, leading to a response in the cell

Cells containing the receptor for a specific ligand that can respond to the binding of the ligand to the receptor. Cells cannot respond to ligands for which they do not have the appropriate receptor

Proteins within the cell that bind to ligands. These cytoplasmic receptors typically bind to hydrophobic ligands that have crossed the membrane of the cell and entered the cytoplasm

A series of chemical reactions in which each molecule activates multiple molecules amplifying the cell’s response to a signal

Enzymes that add phosphate groups to other molecules, often activating those molecules

Enzymes that remove phosphate groups from other molecules, often deactivating those molecules

An enzyme that converts ATP into the secondary messenger cyclic AMP. Cyclic AMP is an important secondary messenger in cell signaling

Intracellular signaling molecules that create chemical changes in a cell in response to the reception of chemical signals. Examples of secondary messengers include cyclic AMP and the calcium ion (Ca2+)

A secondary messenger formed from ATP by the enzyme adenylyl cyclase

Negative feedback occurs when a stimulus triggers a response that returns the system to homeostasis. For example, an increase in body temperature in humans triggers sweating, which reduces the body temperature

Positive Feedback occurs when a stimulus triggers a response that increases the strength of the stimulus, moving the system further from homeostasis. An example of this is ethylene, which stimulates fruit ripening. Ripening fruit releases more ethylene, which will stimulate even faster ripening