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Cell Membranes Problem Set

Problem 3: Hydrophobic Forces


Placing phospholipids into an aqueous solution immediately results in their forming a lipid bilayer. What is the driving force causing this ordered arrangement ?

A. The phospholipids are very ordered in water, and gain freedom of movement by forming a bilayer.

Water, when associated with lipids, is forced into an ordered arrangement with fewer hydrogen bonds. Forcing lipids into a bilayer gains freedom of movement for the water.

Yes, the water can avoid very unfavorable arrangements by "squeezing" phospholipids into a bilayer, sequestering the hydrophobic fatty acid tails inside the membrane. Once formed, the membrane is further stabilized by the other weak forces, including van der Waals contacts between fatty acids, and hydrogen bonding and electrostatic attractions between the hydrophilic part of the phospholipids and the aqueous solution.

C. Phospholipids have a strong affinity for other phospholipids, leading to self assembly.

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