How does biochemistry describe life processes?
Living organisms, such as humans, and even the individual cells of which they are composed, are enormously complex and diverse. Nevertheless, certain uni- fying features are common to all living things from the simplest bacterium to the human being. They all use the same types of biomolecules, and they all use energy. As a result, organisms can be studied via the methods of chemistry and physics. The belief in “vital forces” (forces thought to exist only in living organ- an underlying unity throughout the natural world.
Disciplines that appear to be unrelated to biochemistry can provide answers to important biochemical questions. For example, the MRI (magnetic resonance imaging) tests that play an important role in the health sciences originated with physicists, became a vital tool for chemists, and currently play a large role in biochemical research. The field of biochemistry draws on many disciplines, and its multidisciplinary nature allows it to use results from many sciences to answer questions about the molecular nature of life processes. Important applications of this kind of knowledge are made in medically related fields; an understanding of health and disease at the molecular level leads to more effec-tive treatment of illnesses of many kinds.
The activities within a cell are similar to the transportation system of a city. The cars, buses, and taxis correspond to the molecules involved in reactions (orseries of reactions) within a cell. The routes traveled by vehicles likewise can be compared to the reactions that occur in the life of the cell. Note particularly that many vehicles travel more than one route—for instance, cars and taxis can go almost anywhere—whereas other, more specialized modes of transporta-tion, such as subways and streetcars, are confined to single paths. Similarly, some molecules play multiple roles, whereas others take part only in specific series of reactions. Also, the routes operate simultaneously, and we shall see that this is true of the many reactions within a cell.
To continue the comparison, the transportation system of a large city has more kinds of transportation than does a smaller one. Whereas a small city may have only cars, buses, and taxis, a large city may have all of these plus oth-ers, such as streetcars or subways. Analogously, some reactions are found in all cells, and others are found only in specific kinds of cells. Also, more structural features are found in the larger, more complex cells of larger organisms than in the simpler cells of organisms such as bacteria.
An inevitable consequence of this complexity is the large quantity of ter- minology that is needed to describe it; learning considerable new vocabulary is an essential part of the study of biochemistry. You will also see many cross- references in this book, which reflect the many connections among the pro- cesses that take place in the cell.