Which of the following is the most membrane permeable?
a. RNA
b. Ca2+
c. Glucose
d. Water
e. N2
I know it can't be a, b, or c... But is N2 or water more permeable? I'd really appreciate it if someone would explain why
a. RNA
b. Ca2+
c. Glucose
d. Water
e. N2
I know it can't be a, b, or c... But is N2 or water more permeable? I'd really appreciate it if someone would explain why
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The two outer faces of the membrane are charged and hence hydrophilic. The interior of the membrane is hydrophobic which acts as barrier to hydrophilic, charged molecules. So anything that is large, electrically charged or both will not be able to penetrate the membrane unless there is a protein channel or transport mechanism. Of your choices, only nitrogen gas (N2) matches those requirement in that it is not charged and is a small molecule. So it can freely diffuse across the membrane.
Water is also very small but is highly charged because it contains two oxygen-hydrogen polar bonds. So some water does diffuse through the membrane by slipping between the lipids but much of the water is blocked by the hydrophobic interior of the membrane. The remaining molecules/ion are even larger and all charged so they cannot pass through the membrane at all.
Water is also very small but is highly charged because it contains two oxygen-hydrogen polar bonds. So some water does diffuse through the membrane by slipping between the lipids but much of the water is blocked by the hydrophobic interior of the membrane. The remaining molecules/ion are even larger and all charged so they cannot pass through the membrane at all.