Fill in the gaps with the following words. disadvantages / composed of / wires / axis / liquid / spin / homogeneous / angles / repel

disadvantages / composed of / wires / axis / liquid / spin / homogeneous / angles / repel

1. In the PNS, both myelinated and unmyelinated axons are bundled together, much like ______________ in a cable, to form nerves.

2. Plant cell suspension culture involves the growth of single or small groups of plant cells in a ______________ growth medium.

3. One of the ______________ of external gills is that they must constantly be moved or the surrounding water becomes depleted in oxygen.

4. Clearly polymorphism can appear within an initially uniform bacterial population growing in a simple ______________ environment.

5. Hemoglobin is a protein ______________ four polypeptide chains and four organic compounds called heme groups.

6. The polar water molecules ______________ the long nonpolar tails of the phospholipids as the water molecules seek partners for hydrogen bonding.

7. Electrons ______________ around the nucleus a far distance away from the nucleus.

8. An imaginary plane perpendicular to the ______________ of the spindle that passes through this circle is called the metaphase plate.

9. Centrioles occur in pairs, usually located at right ______________ to each other near the nuclear membranes.

Translate into Russian

1. This does not mean that every oxidative deamination of a base in RNA causes a mutation, but rather that when a suitable base is changed the mutation takes place. Nor does it mean that all mutations are caused by single modification of a single base in the polynucleotide chain.

2. Many examples of this have been seen in earlier chapters; perhaps, the most striking are the pit studies.

3. Closely relating to the problem of determining the nature of the active centers of enzymes is the problem of finding out what reactions are undergone by the active centers when the enzyme-substrate complex is formed.

4. Not only does the direction of diffusion of a substance depend upon the relative concentration of that substance, but the speed of diffusion also depends upon relative concentration.

5. The greater the difference in the relative amounts of a substance in different places, the more rapid is the rate of diffusion.

6. Of somewhat less importance is the degree of diffusion.

7. If the molecules are complex, however, in only a small fraction of the collisions will the molecules come together in the right way.

8. Only in the region of pH 4 or lower could one expect to find a reasonably stable oxidation product.

9. Superimposed on all this is the tremendous significance of energy transfer, one of the very basic signs of life.

10. Of more interest was the observation that a new substance, behaving in all respects toward the enzyme like catechol, was formed.

11. Not until fairly recently, however, have active RNP particles been prepared from tissues like liver.

12. Of greatest importance appears to be the finding that this synthesis is inhibited more than the incorporation of amino acids.

UNIT 15 Models, Heterogeneity, and Scale

A model is a simple representation of a more complex form or phenomena. The term "model" is general and no interpretation of data is possible without resort to some kind of model; whether implied or explicitly declared. Many kinds of models exist and we will emphasize deterministic, mathematical models of physical and biological systems with some considerations of probability formulations. The description of natural phenomena can vary along a continuum of complexity from the trivial to the incomprehensible, and the appropriate level of complexity depends on the purpose. The application of fundamental principles to natural phenomena frequently requires adaptation of those principles or creative simplification of the natural system so that it reasonably conforms to the requirements of the underlying principles. Creative simplification of natural materials or phenomena is the "art" of environmental biophysics, and its practice depends on one's understanding of relevant fundamentals; a purpose of this book. Clearly, questions can be posed that require solutions of staggering complexity. All of nature is exceedingly complex, perhaps infinitely complex; however, insight can be gained into its complexity through the simplicity of a model. As Albert Einstein is purported to have said: "Everything should be made as simple as possible, but not simpler."

The relation between the spatial scale of some desired prediction or understanding and the scale of heterogeneity inherent in the system is essential to the process of simplification. Materials in nature tend to be heterogeneous, not pure. One of the distinguishing features of human activity is the tendency to categorize nature into its elements, purify the naturally occurring mixtures, and reassemble the pure elements into new arrangements. In nature, homogeneous materials, which are materials with uniform properties throughout their volumes, tend to be rare. Obviously, if we go to fine enough scale, nothing is homogeneous; therefore homogeneity depends on spatial scale. In environmental biophysics we consider natural materials such as soil, rock layers, vegetation mixtures, and animal coats. The principles that are commonly used in environmental biophysics are most easily understood and used with pure materials.

Define the following words using a dictionary

Trivial, incomprehensible, staggering, to purport, exceedingly, inherent, pure, fine

Complete the sentences

1. The term "model" is general…
2. The application of fundamental principles to natural phenomena frequently requires...
3. Creative simplification of natural materials or phenomena is…
4. Clearly, questions can be posed that…
5. All of nature is exceedingly complex, however…
6. One of the distinguishing features of human activity is…
7. Obviously, if we go to fine enough scale,…