Question

Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest).

a. estrogen > propanol > sodium > alanine
b. alanine > propanol > sodium > estrogen
c. estrogen > propanol > alanine > sodium
d. sodium > propanol > alanine > estrogen

Answer 1

c. estrogen > propanol > alanine > sodium

Step-by-step explanation:

The phospholipid bilayer is formed by amphoteric lipids, the nonpolar region is inside the bilayer, so the diffusion of nonpolar molecules are easy (nonpolar reacts with nonpolar) and generally occurs passively (without loss of energy). With the increase of the polarity, the diffusion became difficult and slow. All the molecules are shown below.

Estrogen has two points of polarity in its hydroxides, but the carbon rings stabilize the molecule, and it has low polarity. Then, propanol has only one hydroxide and is the second-lowest polar molecular. Alanine has two points of polarity because oxygen and nitrogen have high electronegativities. Then, the ion sodium has a charge and has no stabilization such as the molecules, so it is the most difficult to diffuse.