8.6 Self Assembly In Cells

How can amphiphilic molecules account for their hydrophobic tale in a water environment? Figure 8.5 solves this self-assembly by using a sphere. To form a sphere the hydrophilic head must be wider than its tail. Not all amphiphiles can take this arrangement, for example two tailed molecules can form a bilayer membrane.

These two tailed amphiphiles are usually of the class phospholipids. These are the major component of cell membranes. The reasons for this are:

• Self-assembly of phospholipids is more frequent than one chain surfactants because the hydrophobic cost of two chains exposed to water is twice as great as a single chain
• Phospholipids spontaneously form closed surfaces (vesicles) to avoid exposing hydrocarbon chains
• They are easy to synthesis in cells
• The permeability of phospholipids membranes have favourable values
• The fluid mosaic allows ease of changing shape
• The fluid mosaic can accept embedded objects

All these factors make a working cell possible.