Fill in the gaps with the following words. orders / limit / broader / network / prescribed / applicable / individual / correspondingly

orders / limit / broader / network / prescribed / applicable / individual / correspondingly

1. Fibers are abundant in some kinds of wood, such as oak, and the wood is ______________ dense and heavy.

2. At a ______________ scale, populations are often most densely populated in the interior of their range and less densely distributed toward the edges.

3. To produce these enzymes, genes are transcribed in a carefully ______________ order, each for a specified period of time.

4. The efficiency of oxidative respiration at harvesting energy establishes a natural ______________ on the maximum length of food chains.

5. Species are often composed of a ______________ of distinct populations that interact with each other by exchanging individuals.

6. The structure of the thigh bone clearly indicated that the ______________ had long, straight legs and was an excellent walker.

7. Because of the diversity of living organisms, no single definition of what constitutes a species may be universally ______________.

8. A number of insect ______________ that are particularly associated with flowers appeared or became more abundant during the rise of angiosperms.

Translate into Russian

1. It is the phenotype which is observed in breeding experiments, and inferences about genes are made from the segregation of phenotypic differences.

2. This experiment demonstrates beautifully that it is primarily DNA which enters the host cell, leaving most of the protein outside.

3. In order to possess the specificity necessary to account for gene action, the gene as a functional unit of genetic material must consist of many nucleotides; it is only in a polynucleotide that different base sequences can be achieved.

4. It is with microorganisms that the reversibility of mutation can be studied most easily, for among them it is relatively easy to select either forward or back mutants by manipulating the environment.

5. When the factors are chromosomal genes, it is the chromosome that is mapped.

6. In multicellular forms it is the zygote which divides asexually, the associated mitoses ensuring a population of diploid somatic cells.

7. Most malignant cell lines which have been examined are hypotetraploid; thus, it is the presence of additional chromosomes above the diploid number which is significant.

8. It is the smallest distances which reveal the resolving power of genetics, and from them we can see that units as small as one millionth, of the linkage map can be identified, measured, and, to some degree, characterized.

9. It is about this period (1940) that the studies of H. A. Barker and his colleagues, in Berkeley, California, on the basis of comparative biochemistry, began to clear up the intermediate steps to the synthesis of fatty acids.

10. It was shown that the prosthetic groups, in this case the carbon monoxide derivative of haem, were similar in the two compounds, and it was therefore in the protein moiety that they differed.

11. It is this crystallization that distorts the red cell into a sickle shape.

12. It is with great interest that we may look forward to a description of similarities between the subunits of the haemoglobins of various species.

13. It was not, however, until much later that evidence began to appear which indicated that RNA was not only associated with protein synthesis, but was essential to it.

14. It is this force of attraction between water molecules which leads to the high latent heat and high surface tension of water, since a relatively large amount of energy is needed to separate a water molecule from its neighbours.

15. It was in 1939 that the real start was made toward the determining of the role of phosphates in the oxidation of what we now call the Krebs cycle substrates.

16. In most, instances, it is the RNA in the nucleolus that is the most radioactive, as indicated by radioautographic experiments.

17. It is the particles in the cell that are responsible for the basophilia, for it is the RNA of these ribosomes that combines with the basic dyes.

18. It was this work which led to the first direct experimental evidence for the participation of free radicals in the one electron enzymic electron transfer.

19. It is only in this form that the energy of the foodstuffs can serve as fuel for the living machinery.

20. It was J. Weiss who, in 1942, gave the first clear formulation of the idea that within a complex an electron of one of the two complexing molecules may be transferred to an orbital of the other.

21. In this case it is the energy of the absorbed photon which lifts the electron of the donor molecule to the excited level of the acceptor.

22. It is for this reason that Mulliken calls such a spectrum a «charge transfer spectrum» which is characteristic for the complex.

23. It was evidently the memory of the early demonstration which led me back to these reactions.

24. It is this speculation which allows me to make for the first time, after twenty years of muscle research, an intelligible picture of how ATP could drive muscle.

25. It is at these active centers that the enzymes combine with the Substrates and at which chemical reaction occurs.

UNIT 14 Thermal Molecular Movement

The disadvantage of the method of illustrating structures of organic molecules by using mechanical models composed of spheres and connecting wire axes, as well as of computer simulations of molecular structures, is their suggestion of a more or less static point of view. In reality, however, in liquids as well as liquid-crystalline phases, the molecules are always in a state of vigorous thermal motion. The following three forms of molecular movements are to be considered: vibrations, rotations, and translations.

Vibrations are oscillations in the binding distances between the atoms in a molecule. The term rotation means not only the rotation of the whole molecule, but additionally, the spin of individual atoms or atomic groups around the axes of their bonds. Of course in this case the intramolecular interactions of the atoms are to be considered. So, for example, considering a simple molecule of ethane, the rotation around the CH₃—CH₃ bond cannot be homogeneous. Energy minima of rotations occur periodically every 120°. Hence, rotation is "locked" at certain angels of low energy levels.

A covalent bond, rotating around its angle relative to another, consequently describes a cone. The next bond rotates, as well, but it does so quasi on the spot, moving itself in an orbit of that lateral cone surface. In this way chain molecules can assume a stochastic orientation unless other strong attracting or repelling interactions between the monomers are preventing this. The molecular structures resulting in this way can be calculated by the laws of statistical thermodynamics.

The so-called random flight model allows the simplest description of the behavior of a long molecule. In this case, the real molecule is described as a sequence of segments with length l. These segments are connected to each other in such a way that the orientation of each is independent from the orientation of the former segment. This random flight chain is characterized by the length (l) and the number (n) of its segments. The positions of the end points of the segments can be expressed as vectors in a polar coordinate system which is based on the center of gravity of the molecule. The distance between the endpoints of such a molecule (d_max) at maximal elongation is: d_max = nl.

Define the following words using a dictionary

Vigorous, a disadvantage, rotation, lateral, the spin, polar, covalent, quasi, a cone

Complete the sentences

1. A covalent bond, …

2. The positions of the end points of the segments…

3. These segments are connected to each other in such a way that…

4. The molecular structures resulting in this way…

5. So, for example, considering a simple molecule of ethane,…

6. The term rotation means not only…

7. The so-called random flight model…