Materials like o2 and co2 can move through the bilayer of biological membranes from areas of high to low concentration by .

By diffusion. Diffusion means the net movement of materials from a region of higher concentration to a region of lower concentration down the concentration gradient

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.