Water as a Link between Membrane and Colloidal Theories for Cells

Area of Science:

• Biophysics
• Cell Biology
• Thermodynamics

Background:

• Current cell theories debate the necessity of lipid membranes, with one emphasizing compartmentalization and another viewing cells as colloidal systems.
• Understanding biomembranes requires integrating their structural and thermodynamic roles, particularly the influence of water.

Purpose of the Study:

• To incorporate water as a key structural and thermodynamic component of biomembranes.
• To reconcile competing theories of cell structure by viewing the membrane interphase as a hydrated solution coupled to the hydrocarbon region.

Main Methods:

• Describing the membrane state as an open, non-autonomous, and responsive system using the Thermodynamic of Irreversible Processes.
• Analyzing the interplay of hydration, free energy, water activity, surface pressure, and the Association Induction Hypothesis (AIH).

Main Results:

• The membrane interphase is modeled as a bidimensional hydrated polar head group solution.
• This model reconciles compartmentalization and colloidal theories of the cell.
• Water in confined interphase regions exhibits unique thermodynamic properties influencing H-bonding networks.

Conclusions:

• Biomembranes are open, non-autonomous systems where metabolic events and polymorphic changes are interconnected via hydration.
• Hydration, modulated by water activity and surface pressure, is crucial for understanding lipid properties and the AIH.
• Water's role in interphase H-bonding networks facilitates event propagation between the membrane and cytoplasm in crowded cellular environments.