Molecular Structure of Biological Systems Part 2

The limitation of the degree of freedom of a biochemical reaction is realized by a property of the system which is called anisotropy. In contrast to isotropic systems, like simple solutions, in anisotropic systems the mobility of molecules in various directions is not identical, but is restricted in some directions, and promoted in others. This, for example, is the case for enzymatic reactions, where the participating enzymes are orientated in membranes, or if the reactions of charged or polar reactants occur in strong electric fields of electrical double layers.

In many fields the biological organism works as an amplifier of the microphysical stochastics. A molecular mutation, for examples, leads to a reaction chain, which finally ends with a phenomenological alteration of the organism. Or, as another example: a few molecular events in the pigments of optical receptors can lead to perception and to reaction in behavior.

During the first step in considering molecular mechanisms of biological systems, a further aspect is taken into consideration. Unfortunately, biologists often ignore the fact that a qualitative jump has to be made in the transition from the "visible" macrophysical structures, to the microphysical systems such as atoms or molecules. This includes not only the above-mentioned transition from the deterministic behavior of macroscopic systems to the stochastic behavior of single molecules, but many more aspects as well. The biologists, for example, must acknowledge that the term "structure" receives a new meaning. The visible "biological structure", as known in the fields of anatomy, morphology and histology, now appears as concentration profiles or as systems of electric charges or electromagnetic fields. Instead of visible and measurable lengths, diameters or distances, as common in the visible world, in the microphysical world so called effective parameters are used. These sorts of parameters are exactly defined and they can be measured with arbitrary exactness, but they do not correspond to some visible boundaries. A single ion, for example, has no diameter in the sense of the diameter of a cell, or a cell nucleus, which can be measured by a microscopic scale. In the following sections we will define effective parameters like crystal radius, hydration radius and Debye-Hiickel radius, which really are important parameters for functional explanations.

Define the following words

Isotropic, anisotropy, perception, macrophysical, arbitrary, hydration, alteration.

Continue the sentences

1. In contrast to isotropic systems…

2. A molecular mutation, for examples, leads to…

3. During the first step in considering molecular mechanisms…

4. Unfortunately, biologists often ignore the fact that…

5. This, for example, is the case for enzymatic reactions, where…

6. This includes not only the above-mentioned transition…

7. The biologists, for example, must acknowledge that…

8. These sorts of parameters are exactly defined…

Put the following words and word combinations into the gaps

property / solutions / restricted / promoted / occurs / corresponding / boundaries / measure

In mammals, gas exchange ______________ across millions of tiny air sacs called alveoli.

Polar and charged amino acids are ______________ to the surface of the protein except for the few that play key functional roles.

The single most outstanding chemical ______________ of water is its ability to form weak chemical associations with only 5 to 10% of the strength of covalent bonds.

Despite their unicellularity, ciliates are extremely complex organisms, inspiring some biologists to consider them organisms without cell ______________ rather than single cells.

Atherosclerosis is ______________ by genetic factors, smoking, hypertension (high blood pressure), and high blood cholesterol levels.

Plants use light receptor molecules to ______________ the length of night.

Seasonal changes in wind circulation produce ______________ changes in ocean currents.

A bubble, such as those produced by soap ______________, is a hollow spherical structure.