One of the grand challenges in biology is understanding how the first cells formed on Earth. Since all cells are bound by a cell membrane, origin of life researchers are interested in modeling what the first membranes may have been like. What types of molecules might these researchers consider to be the original building block of cell membranes?

a) Hydrophobic molecules
b) Amphipathic molecules
c) Hydrophilic molecules
d) Insoluble molecules

The correct answer to the question is: b) Amphipathic molecules.

Explanation:

The membrane structures are composed of molecules having both hydrophobic and hydrophilic regions. These are called Amphipathic molecules.The hydrophobic region is formed of water insoluble lipid (fatty acid) molecules which tend to avoid contact with water and so remain in the interior of the membrane.The hydrophilic region is formed by water soluble phosphate groups which forms hydrogen bonds with the water molecules and so remain on the surface of the membrane.Therefore, a membrane is formed from by a phospholipid bilayer, that is, two layers of phospholipid polymer where the lipid part is directed towards the centre away from water and the phosphate part towards the surface in association with water molecules.A single phopholipid moiety is composed of a glycerol molecule which forms two ester bonds with a phosphate group and a fatty acid molecule.