Chapter 11 Cell Communication

Local Signaling

direct contact between two cells in which a short distance is traveled

cell junctions

directly connect the cytoplasms of two neighboring cells

Synaptic signaling

a neurotransmitter is released in the nervous system from a cell and travels across the synapse to bind to the neighboring cell

endocrine signaling

specialized cells release hormones that travel to target cells via the circulatory system

Stages of cell signaling

reception, transduction, response

Reception

a cell detects a signaling molecule that binds to a ____ protein on the cell surface, causing the protein to change shape

transduction

the binding of the signaling molecule alters the receptor and initiates a signal ____ pathway within the cell

response

specifically triggered by the transduced signal in the target cell

ligand

the signal molecule that can only bind to a specific receptor

membrane receptors

g-protein coupled receptors, receptor tyrosine kinases, ion channel receptors

g-protein coupled receptors (GPCRs)

surface transmembrane receptors that work with the help of a g-protein. All have similar structures, and their systems are widespread with diverse functions

receptor tyrosine kinases (RTKs)

membrane receptors that attach phosphates to tyrosines using kinases and can signal multiple signal transduction pathways at the same time

ligand-gated ion channel receptors

allows specific ions to pass through a channel in the membrane through the receptor

intercellular receptors

found within the cell in the cytoplasm or nucleus of target cells. Signaling molecules have to enter the cell prior to binding the receptor

transduction

triggered by the binding of the signal molecule to the receptor

transduction cascades

multiple steps; receptor activates another protein, which activates another until the protein producing the response is activated

protein phosphorylation and dephosphorylation

widespread cellular mechanism for regulating protein activity. Acts as a molecular switch, turning activities on and off or up and down as required

protein kinases

transfer phosphates from ATP to proteins

dephosphorylation

rapidly remove the phosphates from proteins

second messengers

small, nonprotein water-soluble molecules or ions that spread throughout a cell by diffusion (cAMP & calcium ions)

nuclear response

many signaling pathways regulate the synthesis of enzymes or other proteins, usually altering gene expression or turning genes on and off

cytoplasmic response

regulates the activity of enzymes rather than their synthesis

signal regulation

amplification, specificity of the response, overall efficiency of the response, termination

signal amplification

cascades the cell’s response

Scaffolding proteins

large proteins to which other proteins attach. Can increase the signal transduction efficiency by grouping together different proteins in the same pathway