What are the several different membrane transport mechanisms that various substances use to pass through the plasma membrane?

Aneuron is stimulated with an electric pulse. the action potential is detected at a point 3.70 cm down the axon 0.0052 s later.when the action potential is detected 7.20 cm from the point of stimulation, the time required is 0.0063 s. what is the speed of the electric pulse along the axon? (why are two measurements needed instead of only one? )

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

About how much of the cell mass is watet