The Chemistry of Biology and IMFs

There is a perpetual overlap between the two studies of biology and chemistry. Biology borrows many of its principles from chemistry and there is example after example of this relationship. The area offers a great fascination for me and I believe it might for you as well. Needless to say, when we can combine chemistry principles with the phenomena that we see, we then become capable of really understanding how biology works and how it is chemistry that makes life and its nuances work.

One fundamental principle that is addressed within chemistry are the Intermolecular Forces (IMFs). Intermolecular forces span several notable types of interactions; dipole-dipole forces, hydrogen bonding, and London Dispersion forces. Dipole-dipole forces are found within polar molecules and are created when there is a charge disparity which causes one side to take on a permanent partial charge (negative or positive). When an area of a molecule is more electronegative and is not balanced out, it has the ability to create the charge disparity by almost locking electrons more to one side of a bond, thus giving the molecule partial charges due to polarizing the bond. Hydrogen bonding is a unique form of dipoles in and of itself, and the special thing to note is that it specifically involves hydrogen atoms bonded to one of three very electronegative atoms. Only two apply to forming hydrogen bonds and those are nitrogen and oxygen. The final IMF to mention is London Dispersion forces which are attractive forces that occur only temporarily within non-polar molecules when temporary dipoles are formed.

An example of forces acting in a macroscopic fashion is displayed well by the fascinating adaptation of the gecko. The gecko toe pad is something rather unique in the animal kingdom, it doesn’t need to secrete substances to stick itself to surfaces and instead uses many small forces to hold itself on them. It utilizes van der waals interactions, weak interactions between temporary dipoles created in non-polar substances. The less compact the molecules and the longer they are, the more they are able to be polarized. Since there are so many parts to the larger molecules, the functional groups can all go to stabilize the molecule when temporary dipoles form and thus temporary dipoles are much more common. Geckos capitalize on this fact and if one were to examine their toe pads they would be able to notice this. Looking at their toes under a microscope shows that they actually are coated in many small hair-like protrusions which branch at their tops to form even more minute versions of the protrusions. This adaptation allows the surface area of the toe pads to be massive and takes every advantage of the otherwise small forces.

There is one really good instance worth noting where they would not be able to climb, “if we put a gecko on a surface that can’t contribute to van der waals forces, like a nonstick pan, well the gecko can’t grip” (It’s Okay to Be Smart, 4:43). The channel has a very interesting display of this such ability in their episode: The Lizard That Uses Nanotechnology to Walk Upside Down. As a note, non-stick pans tend to be coated in a substance called PTFE. PTFE disables the gecko’s ability to scale surfaces because it lacks the ability to be thoroughly polarized. PTFE is short for polytetrafluoroethylene, which when polymerized forms a super stable substance and PTFE is so stable that it doesn’t really allow for temporary dipoles, the internal dipoles cancel each other out and leave the collective structure very non-polar and largely incapable of forming IMFs and thus defeating the gecko. Regardless of the one instance, geckos have an amazing ability and they put IMFs under the spotlight, openly showing them off for the credit they deserve.

About Mr. Mohn

Biology Teacher

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