Cellular Commumication

juxtaposition signaling

• signaling between adjacent cells

• cells touching each other can form pores that allow signaling molecules to move directly to their neighbor

• or signaling molecules can interact with a receptor on a neighboring cell

juxtaposition signaling

paracrine signaling

paracrine signaling

• signaling between nearby cells

• signaling molecules are released by a source cell

• signaling molecules go into some extracellular fluid and by diffusion travel to a nearby cell or back to itself (not the one right next it)

synaptic signaling

• nerve cells send electrical signals, which cause release of neurotransmitters

• neurotransmitters are relased by vesicles after the electrical signal has traveled down the nerve cell

• vesicles fuse with the membrane and squirt out the neurotransmitters that then travel across the synapse (the short space between nerve cells)

• the nuerotransmitter then interacts with some receptor in the receiving nerve cell

endocrine signaling

• signaling between distant cells

• signaling cells release a signaling molecule and then it travels through the bloodstream to a target cell in an entirely different part of the body

endocrine signaling

what happends when a signal molecule is released

• all cells in range will receive the signal

• only cells with a receptor tuned to the specific signal can respond to the signal

what does responding mean?

• some change in cellular activity

  • gene expression

  • enzyme activity

  • cell division

• specific ligand interacts with a specific receptor

  • binding leads to a conformational change

  • shape change leads to functional change

ligand

signal molecule

most chemical signals are ____________

most chemical signals are hydrophilic

Because chemical signals are hydrophilic, _____________________

Because chemical signals are hydrophilic, they cannot pass through the membrane without some sort of help

most receptors are ________

most receptors are transmembrane proteins

types of chemical signals

• lipid soluble signals (hydrophobic)

• water soluble signals (hydrophillic)

lipid soluble signals

• pass through the plasma membrane and bind to a specific receptor in the cytoplasm or in the nucleus

• activated receptor ligand complex regulates genes by binding to DNA

water soluble signals

• cannot pass through membrane

• binds to specific plasma membrane receptors

• the receptore ligand complex activates a cascade of events in the cell

intracellular receptor (molecule is hydrophobic) and goes right through the hydrophobic core

intracellular signaling

• receptors found in the cytoplasm or in the nucleus

• signal must be hydrophobic or very small to diffuse through membrane

  • steroids

    • cortisol

  • nitric oxide

  • thyroid hormone

membrane bound receptors

• ex. ligand-gated ion channel

• allows hydrophillic molecules in

G protein coupled receptor

• ligands bind to the receptor and GDP becomes phosphorylated and activates the G protein

• the activated G protein is then going ot interact with an effector protein

enzyme-linked receptor

receptor is also an enzyme and triggers and enzamic response

signal transduction pathway

• a series of steps triggered by the receptioin of a signal that eventually leads to a biochemical response

• intermediate steps often involve activation or inativation of enzymes

• the most common regulatory step is the addition or removal of a phosphate group

protein kinase

general name for an enzyme that helps catalyze the addition of a phosphate group from ATP to a protein