A mixed solution of water and small molecules is exposed to a cell membrane and allowed to interact for an hour. Which molecule would be most likely to cross the phospholipid bilayer without the aid of transport proteins and diffuse across the membrane the fastest?

A. O2
B. Estrogen (C18H24O2)
C. NH4+
D. Na+
E. CH3COO-


Answer: A

Biology & Microbiology

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