Structural hierarchy in cells

FIGURE 1-11 Structural hierarchy in the molecular organization of cells. In this plant cell, the nucleus is an organelle containing several types of supramolecular complexes, including chromosomes. Chro-... 

Each class of molecules has a similar structural hierarchy subunits of fixed structure are connected by bonds of limited flexibility to form macromolecules with three-dimensional structures determined by noncovalent interactions. These macromolecules then interact to form the supramolecular structures and organelles that allow a cell to carry out its many metabolic functions. Together, the molecules described in Part I are the stuff of life. We begin with water. 

Thus, autocatalysis occurs in biology across various levels of structural and functional hierarchies, from a complete plant (or fungus, animal) over single cells down to such molecules which take part in metabolism and get doubled in cell budding and reproduction also. Both the... 

Now, as to the structure of the new edition. Essentially, it follows the old in that Chapter 1 introduces the basic chemical terms to those who are unfamiliar with them, and Chapters 2 and 3 deal respectively with the properties of the small and giant molecules of which the cell is composed. In the earlier edition, the structure of the. cell itself was not discussed until much later this time, and because of the importance we attach to showing some subcelluiar organelles as composed of higher order hierarchies of macromolecules, the account of the cell forms Chapter 4. This concludes the section on biochemistry as analysis, and we turn in Chapters 5 and 6 to work, enzymes and metabolism. The core of biochemical energetics and metabolism is in Chapters 7 and 8, and it is these... 

Certain properties, common to all types of macromolecule, can be derived from such analyses. All seem to have a certain individuality and many have the ability to specifically recognize and interact with other substances. They are all, to a greater or lesser extent, flexible molecules, capable of adapting their shape in response to their particular microenvironment within the cell. They ail have a pronounced intolerance to extreme conditions, a fragility that makes them fall apart if treated harshly. Finally they all may be described in terms of a structural hierarchy of primary, secondary and tertiary structures that we need to look at in a little more detail. 

Fig. 1). As was shown above, atoms, common molecules, macromolecules, microbodies, cells, tissues. .. an oiganism, population etc. are meant under hierarchical structures. This, in essence, means that the evolution of lower-hierarchy stmctuies proceeds much quicker than that of the organism itself, whose biomass serves the environment for its atoms, molecules, cells, etc. Just in this connection, for every biosystem it is possible to isolate its habitation medium, i.e., a peculiar thermostat with certain parameters. Such quasi-closed subsystems possessing their own thermostats, uniting, form athermod5mamic system of a higher hierarchical level. 

---