Question

Which of the following phenomena in cell membranes is energetically expensive and does not occur spontaneously?

• A. \( \text{The rotation of membrane proteins} \)
• B. \( \text{The rotation of phospholipids} \)
• C. \( \text{The lateral diffusion of phospholipids} \)
• D. \( \text{The flip-flop movement of phospholipids} \)

Hint:

Membrane asymmetry influences cellular processes such as signaling, apoptosis, and vesicle trafficking.

Answer 1

The Correct Option is D

The flip-flop movement of phospholipids is energetically expensive because it requires crossing the hydrophobic core of the lipid bilayer. Unlike lateral diffusion, which is spontaneous, flip-flop movement requires specialized enzymes like flippases and scramblases. This process is critical for maintaining membrane asymmetry and lipid distribution.