Phospholipids make up most of the lipid part of the cell membrane.Since water exists on both the outside and inside of a cell,which of the following phospholipid arrangements makes the most sense?
A) a single layer of phospholipids with the polar heads facing outside the cell
B) a single layer of phospholipids with the polar heads facing inside the cell
C) two back-to-back phospholipid layers with the polar heads facing out on both sides
D) two back-to-back phospholipid layers with the non-polar tails facing out on both sides

Question

Quizplus · Accepted Answer

The most logical arrangement for phospholipids in a cell membrane is to have two back-to-back layers with the polar heads facing out towards the water both inside and outside the cell. This creates a hydrophobic, nonpolar interior of the membrane that functions as a barrier to the passage of water-soluble substances. Option A and B are not possible because a single layer of phospholipids would not be stable in an aqueous environment. Option D is also incorrect because it would result in a hydrophilic interior of the membrane, which would not provide an effective barrier to solutes.

Phospholipids Make Up Most of the Lipid Part of the Cell