Signal Transmission and Osmolarity and other stuff

Hydrophilic signaling molecules chain of events

bind to extracellular receptors, initiate second messenger cascades, and alter ion channel conformations.

speed of hydrophilic signaling molecules

they have a fast effect as they are just modifying already existing proteins, and are then metabolized/excreted quickly

hydrophilic signaling molecule example

norepinephrine

hydrophobic signaling molecular chain of events

typically binds to intracellular receptors and then alter gene transcription and protein synthesis (these can cross the plasma membrane because they are fat loving, they just diffuse which means their receptors are technically intracellular)

how fast are hydrophobic signaling molecules

they have a slow effect as they are building new things and are metabolized/excreted slowly

example of hydrophobic signaling molecules

steroids

autocrine transmission

releases signaling molecule which then reattaches to itself (tells cell it has released enough)

paracrine transmission

signal goes to a nearby neighboring cell receptor, it is very quick and not diluted in blood stream 

endocrine transmission

goes from a cell through the bloodstream to another cell, takes awhile and is usually to a far target (cells communicating with a large swab of tissues)

aquaporins

pathway for water to cross most cell membranes

primary active transport

requires energy source to directly transport substance across the plasma membrane, requires transmembrane proteins (pumps) and pumps agains the concentration gradient (maintaining the gradient)