Question

A molecule is found to be able to diffuse across a membrane. Which of the following characteristics would best describe this molecule? Question options: hydrophobic negatively charged polar neutral hydrophilic

Answer 1

Almost all biological membranes are phospholipid bilayers, so if the membrane stated here is same then the most important property driving the diffusion of a molecule is the hydrophobicity, then neutral molecule diffuse better and finally the small molecules can pass easily.

So, here i will tell you why hydrophobic molecules move better. the membrane is made up of phospholipid bilayer i.e. 2 layers of phospholipid which have 2 components a glycerol head and 2 fatty acid chains. The head is hydrophilic and tail are hydrophobic so the interior of the layer is hydrophobic. So, when a hydrophobic molecule come near the membrane the outer hydrophilic region push it into the midde and then it goes to interior.

Then comes the charge neutral molecules will not interact with the amino acids inside the bilayer so can move easily.

Diagram of the bilayer is given below.

Cp Hydno hobo Cone 0