Question

Describe the influences and forces driving the formation of the lipid bilayer. Briefly discuss the effect of a phase transition on a lipid bilayer

Answer 1

The influences and forces driving the formation of lipid bilayer  is spontaneous because of the hydrophobic interactions and energetically favorably structure. Other intermolecular forces such as Van der Waals, which hold the hydrophobic tails together, and hydrogen bonding, which bind the hydrophilic heads with water, help stabilize the lipid bilayer structure.

The lipid bilayer Phase Transition (LBPT) often called gel to liquid crystal phase transition which appears to have direct biological relevance.

The phase behavior of the lipid bilayer is determined by the Van der Waals interactions between adjacent lipid molecules. The interaction is mainly governed by two factors:

1) The length of the acyl chain in the lipid
2) The packing of the lipids in the bilayer

Longer tail lipids have more area to interact. This will increase the strength of the interaction and consequently decrease the mobility of the lipid. Therefore at a given temperature a short tailed lipid will be more fluid than an otherwise identical long-tailed lipid.

The degree of unsaturation of the lipid tails can effect the packing of the lipids in the bilayer. An unsaturated double bond can produce a kink in the alkane chain. This kink will create extra free space within the bilayer which allows additional flexibility in the adjacent chains. Unsaturated lipids have a significantly lower transition temperature compare to saturated lipids.