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) two back-to-back phospholipid layers with the polar heads facing out on both sides
B) a single layer of phospholipids with the polar heads facing outside the cell
C) a single layer of phospholipids with the polar heads facing inside the cell
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 the cell membrane is a double layer with the polar heads facing the outside and inside of the cell and the non-polar tails facing each other in the middle of the layer. This is known as a lipid bilayer and it provides a barrier that separates the inside of the cell from the outside environment while also allowing for selective transport of molecules. Therefore, option A is the correct choice where two back-to-back phospholipid layers have their polar heads facing out on both sides.

Phospholipids Make Up Most of the Lipid Part of the Cell