Protein materials structural organization

In addition to water and inorganic solids (salts dissolved in cell fluids, shells, and bones), organisms consist of a mix of organic substances. Some of these are macromolecules (e.g., globular proteins, cellulose). Some combine to form subcellular and tissue structures built with combinations of lipids, proteins, carbohydrates, and some specialized polymers like cutin or lignin (Fig. 10.2). These diverse organic materials cause organisms to have diverse macromolecular, cellular, and tissue portions that may be apolar, monopolar, and/or bipolar. 

The tertiary structure of DNA is complex. DNA does not normally exist as a straight linear polymer, but as a supercoiled structure. Supercoiiing is associated with special proteins in eukaryotic organisms. Prokaryotic organisms have one continuous molecule white eukaryotes have many (e.g. humans have 46). Viruses also contain nucleic acids and their genetic material can be either DNA or RNA. 

In previous sections of this chapter, as well as in chapter 6, we have discussed several reasons why liquid water is so critical for life. To briefly review the salient points (1) Water is essential for driving the formation of the three-dimensional structures of macromolecules. These structures, on which macromolecular function depends, are encoded in a latent form in the linear primary structures of proteins and nucleic acids, but can be manifested only when liquid water is present to foster hydrophobic interactions. (2) The assembly of bilayer membranes from lipids and proteins likewise is driven in large measure by hydrophobic effects. (3) Water in the liquid state is a requirement for most types of transport of materials between organism and environment and between compartments within the organism. (4) Lastly, the... 

It is beyond the scope of this book to go into further details of comparing structural organization in synthetic and biological macromolecules. We cannot resist noting however, that one may consider as the ultimate goal of polymer materials chemistry to synthesize exact and accurate structures of the appropriate monomers in well-defined systems to achieve required functions. Differences in properties and function between man-made polymer parts and biomaterials made up of natural biomacromolecules may well be related to differences in their primary structure and architectural control. Proteins and nucleic acids are precisely defined in their... 

Yamanaka has attempted to use the relative cross-reactivities between cytochromes c of one organism and cytochrome oxidases of another to make a quantitative assessment of evolutionary similarity 440,442,44, and earlier references cited therein). If this method were successful, it would be a powerful adjunct to sequence and structure comparisons since far less material and labor are required to make an activity measurement than to carry out an amino acid sequence analysis or X-ray diffraction study. One critical requirement, of course, is that only strictly homologous proteins are compared. If noncorresponding proteins in two organisms are compared, a spurious estimate of their unrelatedness would be obtained. It is in this context that Yamanaka emphasized the need for a descriptive term for what we have called eukaryotic c. ... 

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