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Cell Membranes Problem Set

Problem 3: Hydrophobic forces

Tutorial to aid answer the question

Placing phospholipids into an aqueous solution automatically results in their creating a lipid bilayer. What is the driving pressure leading to this ordered arrangement?

The phospholipids are incredibly ordered in water, and also obtain flexibility of motion by forming a bilayer.

You are watching: What intermolecular forces stabilize a lipid bilayer?

B. Water, once associated via lipids, is compelled into an ordered plan through fewer hydrogen bonds. Forcing lipids right into a bilayer gains liberty of movement for the water.
C. Phospholipids have actually a strong affinity for other phospholipids, leading to self assembly.




Phospholipids are amphipathic molecules with two hydrophobic fatty acids and also a hydrophilic phosphate-containing group linked to glycerol. When placed in an aqueous solution, water forms a shell around the hydrophobic lipid, a case that not only prevents water from making hydrogen bonds via other water molecules, however likewise reduces flexibility of movement, making the water molecules even more ordered.

Scientists define "entropy" as a measure of disorder. Forcing water to be ordered decreases entropy, a very unfavorable instance. Water gains entropy as soon as the fatty acids are covert in the bilayer. The capacity of water to force hydrophobic molecules amethod is best shown by a mixture of oil and also water in salad dressings. The hydrophobic result forces the lipids away from the water, making a separate layer. Vigorous shaking can mix the 2 phases as soon as we want a mixture of oil and also water for our salad.

Phospholipid bilayer


Once the bilayer creates, further stabilization originates from other weak forces. Van der Waals pressures have the right to outcome from the packing of fatty acid tails inside the bilayer. Hydrogen bonding and also electrostatic attractions (ionic bonds) happen between the hydrophilic groups of phospholipids and also the aqueous solution.

We say that hydrophobic pressures cause the bilayer to develop, and the other weak forces stabilize the bilayer.

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This instance of one weak pressure initiating a structural rearrangement that is then stabilized by other weak forces is repeated many kind of times in thedailysplash.tv.

The thedailysplash.tv Project Department of Biochemisattempt and Molecular Biophysics University of thedailysplash.tv May 2002 Revised: August 2004 Contact the Advancement Team