Question

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that
A)
the integral membrane proteins are not strong enough to hold the bilayer together.
B)
water that is present in the middle of the bilayer freezes and is easily fractured.
C)
hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing.
D)
the carbon-carbon bonds of the phospholipid tails are easily broken.
E)
the hydrophobic interactions that hold the membrane together are weakest at this point.

Answer 1

Answer: E)   the hydrophobic interactions that hold the membrane together are weakest at this point.

The phospholipid bilayer is composed of a two-layered structure of phosphate and lipid molecules. In this cell membrane, the hydrophobic lipid ends are facing inward, whereas the hydrophilic phosphate ends are facing outward. As the hydrophobic interactions are weakest along the middle, freezing temperatures will cause them to break here.