List the four cellular structures common to both prokaryotic and eukaryotic
organisms.

a) Cell membrane:

Cell is the microscopic unit of life whether it be prokaryotic or eukaryotic cell, both have cell membrane to hold on the organelles inside it.

b) Cytoplasm:

Though cytoplasm is not an organelle but generic term that describes everything within the plasma membrane. It is a semi liquid plasmic substance which is filled in the closed cell membrane. Organelles are present in it. It acts as a reservoir for amino acids, and other nutrients used in the daily life of the cell.

c) Ribosomes:

It is a natural protein uniter. It weaves one amino acid to other to form long chains.

d) DNA: Deoxyribonucleic acid:

An extremely long set of molecules which is the most important ingredient of chromosomes and is the material which transfers genetic material in every living organism.

answer; ///(b) it is composed of four protein chains and four heme groups;

the endomembrane system i think