Question

Which statement about membrane phospholipids is not true?

• A. They associated to form bilayers.
• B. They have hydrophobic 'tails'.
• C. They have hydrophilic 'heads'.
• D. They flip readily from one side of the membrane to the other.

Answer 1

The correct option is D They flip readily from one side of the membrane to the other.

Plasma membrane is the outer covering of all cell but in plant cells, it is present below the cell wall. It is mainly composed of phospholipid bilayer structure with embedded proteins. The phospholipids have polar hydrophilic heads on the surfaces and hydrophobic tails buried deep inside the interior of the membrane between the two surfaces. In the two-dimensional plane of a bilayer, thermal motion permits lipid molecules to rotate freely around their long axes and to diffuse laterally within each leaflet, because such movements are lateral or rotational, the fatty acyl chains remain in the hydrophobic interior of the bilayer. Phospholipids are free to diffuse within the hydrophobic core of membranes but not from one lipid-rich region on one surface to an adjacent lipid-rich region on the other surface. Thus, the correct answer is option D.