The assembly rules for making molecules from atoms characterize not only how many covalent bonds a given atom can participate in but also the resulting three-dimensional arrangement of atoms in molecules. Giving an example, briefly discuss an implication of the three-dimensionality of molecules which is significant for understanding biological systems. Water is a polar molecule because of a combination of the polar character of O-H bonds and the fact that they are oriented at an angle to one another. If they were oriented in other ways, water would not have its typical solubilizing, adhesive, and cohesive properties, which play a major role in terrestrial life. Briefly describe lipids as assemblies of atoms, specifying two characteristics of lipids which distinguish them from other macromolecules, and the significance of these characteristics for understanding biological systems.
Lipids are largely hydrocarbons, long chains of carbon atoms with associated hydrogens.
In consequence they tend to be non-polar and hence to be an important component of the boundary layers which separate differing adqueous solutions. They also are a rich store of energy, which can be released by oxidation, the transfer of electrons to oxygen. Biological macromolecules are in general polymers. Name one general class of biological macromolecule and the kind of monomer from which it is constructed, and explain how it can be that there are so many more macromolecules of that class than there monomers from which they are constructed. Proteins consist of long chains of amino acids, of which there are only about twenty kinds.