21. Lipids and Carbohydrates   Previous PageNext Page
       Structure, Energy, and information.

So far we have been talking about molecules that are a part of living organisms, yet are not "vital” in the way that we sense enzymes and nucleic acids to be. For all their useful properties, carbohydrates and lipids still are conventional organic molecules, and seem to belong to the test tube as much as to the cell. They do not have that aura of “specialness” that envelops DNA.

No one has ever suggested seriously that sugars and fats are "alive," but this property has been claimed (naively) at times for both proteins and nucleic acids.

The difference that we instinctively recognize between carbohydrates, lipids, and other organic molecules on the one hand, and proteins and nucleic acids on the other, is that the latter carry information in their structure, in a sense that is not true for any other molecules.

This concept of information creates a qualitative difference between proteins and nucleic acids, and all other molecules, and makes them suitable as the basis for a chemistry of life. What this information is and how it is stored and used is the subject of the next chapters.

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