​Which one of the following changes is energetically favorable and occurs spontaneously in an aqueous solution?​

Correct option is A

Explanation:

• Phospholipids are amphipathic molecules containing a hydrophilic head and hydrophobic tail.
• When placed in an aqueous solution, phospholipids spontaneously self-assemble into a bilayer due to the hydrophobic effect.
• This self-assembly occurs because water molecules energetically favor minimizing interactions with the hydrophobic tails.
• The formation of a bilayer is thermodynamically favorable, as it reduces the overall free energy (ΔG < 0) of the system.
• This is the fundamental principle behind biological membrane formation, making bilayer formation a spontaneous and energetically favorable process.

Thus, the correct answer is option (1): Formation of a bilayer from phospholipid molecules.

Information Booster

1. Phospholipid bilayers form spontaneously due to hydrophobic interactions, reducing entropy associated with water ordering.
2. Bilayer formation is an entropy-driven process, where water molecules are released from surrounding hydrophobic tails, increasing system disorder.
3. Lipid bilayers serve as the fundamental structure of cellular membranes, controlling permeability and communication.
4. Micelles, liposomes, and bilayers are different self-assembled structures based on lipid composition and concentration.
5. The fluidity of the bilayer is influenced by temperature, cholesterol content, and fatty acid composition.
6. Self-assembly is crucial for liposome-based drug delivery systems, enabling controlled release of therapeutic molecules.
7. Membrane proteins integrate within the lipid bilayer, playing roles in signaling, transport, and structural support.

Additional Information

• Option (2) Dispersion of one oil droplet into many small ones
  → This requires energy input (e.g., mechanical agitation) and is not spontaneous due to the increase in surface area.

• Option (3) Tearing of the lipid bilayer
  → Lipid bilayers are highly stable and resist spontaneous tearing. Disrupting the bilayer requires external forces or detergents.

• Option (4) Conversion of a membrane vesicle to a flat bilayer
  → Vesicles (liposomes) are more stable than a flat bilayer due to reduced edge tension. Their conversion to a flat bilayer is not energetically favorable.