50 P. T.S. + Brainliest! (I posted this twice-you can copy and paste your answer for the other one-change it up a bit though)
Transport, receive messages, connect cells together: Identify cells: , which can be connected to either a lipid called: or a protein called: .

Tbh It could be the messaging system

Explanation:

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.