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).

alanine estrogen propanol sodium

(a) alanine > propanol > sodium > estrogen
(b) sodium > propanol > alanine > estrogen
(c) estrogen > propanol > sodium > alanine
(d) estrogen > propanol > alanine > sodium


(d) Estrogen is a steroid hormone and will diffuse the fastest across the membrane. Propanol is a small, uncharged molecule with a polar group. Alanine is an amino acid, and although it has a small, nonpolar side group, amino acids are charged molecules. Sodium is an ion and will move the slowest across the bilayer.

Biology & Microbiology

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