Chapter 11 Cellular Communication

Paracrine

signaling cell acts on nearby target cells by secreting molecules of local regulator

Local regulator

chemical signals that influence cells in vicinity

Autocrine

signal to receptor in own body

Endocrine

specialized endocrine cells secrete hormones into blood stream to act on target cells at distant body site

Neurotransmitter

a signaling molecule that is released across the synapse to a receptor

Synaptic

nerve cells releases neurotransmitters molecules into synapse

Synapse

junction between 2 neurons

Juxtacrine

signaling cells act on target cell that is in physical contact with each other (neighboring cells)

3 steps of cellular communication

reception, transduction, and response

Reception

target cell's detection of a signaling cell molecule coming from outside the molecule

Transduction

converts signal to a form that can bring about a specific cellular response

Response

transduced signal triggers specific cellular response

Ligand

smaller molecule that binds with a larger molecule

Receptor tyrosine kinase

membrane receptors that attach phosphates to tyrosine dimer and can trigger multiple signal transduction pathways at once

G protein-coupled receptors

cell surface transmembrane receptors that work with the help of a G protein to transport signals across the membrane

G protein

bind GTP or GDP to GPCR to activate or inactivate receptor

Ligand-gated ion channel

signal molecule opens up gate letting ions transport into the cell

Ca+

high concentration in ER and is released by IP3

cAMP

carries signal initiated by epinephrine from plasma membrane of liver or muscle cell into cell's interior to initiate the required action

Adenyl cyclase

converts ATP to cAMP in response to extracellular signal which then cAMP broadcasts signal to the whole interior of the cell

Phosphodiesterase

converts cAMP to AMP which stops the extracellular signal

Mating factors

a and alpha secrete specific factor that only binds to receptor on other's cell

Yeast signal transduction pathways

cell finds and contacts partner by detecting direction of pheromone source and polarizing growth towards it

Intracellular receptors

found in cytoplasm or nucleus of target cells

What can pass through the membrane easily through diffusion?

small or hydrophobic chemical messengers

Hydrophobic messengers

steroid and thyroid hormones

Hormone-receptor complex

turns on or off particular genes

Signal amplification

enzyme cascades amplify cell's response to signal

water soluble ligand signaling molecules

bind to specific site on receptor proteins that span plasma membrane

lipid soluble ligand signaling molecules

cross the cell membrane and bind with intracellular molecules (slower rate but longer lasting response)

Benefits of transduction multiple step pathway

signal amplification and fine-tuning

Fine-tuning

different proteins allow cells to detect and respond to different signals and same signal can have different effects in cells leading to multiple pathways

Protein kinases

transfer phosphates from ATP to protein (phosphorylation) which activates molecule

Phosphatases

removes phosphate from protein which deactivates molecule

Membrane proteins

GPCR, receptor tyrosine kinase, and ion channel receptors

Phosphorylation

transfers phosphates from ATP to another molecule

Scaffolding proteins

large relay protein with other relay proteins attached which increases signal transduction efficiency (power strip)

C. elegans model

Ced-9 inhibits Ced-4, with signal Ced-9 is inhibited and Ced-4 is active which activates Ced-3, Ced-3 is the caspase (controls cell suicide)

Apoptosis

programmed cell death which cells are chopped up, packaged into vesicles, and are digested by scavenger cells

Apoptosis signal

death signal can be received inside or outside the cell

Phosphorylation cascade

continuous activation of protein kinase until specific protein is reached, which send cellular response (Christmas tree)