Fatty acids space-filling models

Fignre 12.33. Packing of Fatty Acid Chains in a Membrane. The highly ordered packing of fatty acid chains is disrupted by the presence of cis double bonds. The space-filling models show the packing of (A) three molecules of stearate (Cjg, saturated) and (B) a molecule of oleate (Cjg, unsaturated) between two molecules of stearate. 

Figure 12.11 Space-filling model of a section of phospholipid bilayer membrane. (A) An idealized view showing regular structures. (B) A more realistic view of a fluid bilayer showing more irregular structures of the fatty acid chains.

Fig. 7. X-ray crystal structure of cobra venom (Naja naja naja) phospholipase with bound Ca showing a space-filling model of dimyristoyl phosphatidylethanolamine bound in the catalytic site. The ends of the fatty acid chains stick out of the enzyme and are presumably associated with the micelle or membrane (E.A. Dennis, 1994).

Figure 8.6 Space-filling models of fatty acids. Unsaturated fatty acids do not pack as tightly as saturated acids, and their melting points are lower than those of saturated acids.

The lower melting points of triglycerides rich in unsaturated fatty acids are related to differences in three-dimensional shape between the hydrocarbon chains of their unsaturated and saturated fatty acid components. Shown in Figure 26.1 is a space-filling model of tristearin, a saturated triglyceride. In this model, the hydrocarbon chains lie parallel to each other, giving the molecule an ordered, compact shape. 

---