Fill in the gaps with the following words. bonds / assembly / controversy / stochasticity / properties / precise / limited / enlarging

bonds / assembly / controversy / stochasticity / properties / precise / limited / enlarging

1. The plasma membrane is a complex ______________ of proteins enmeshed in a fluid array of phospholipid molecules.

2. Viruses possess only a portion of the ______________ of organisms.

3. The resulting osmotic gradient causes water to be drawn into the center of the cell mass, ______________ the intercellular spaces.

4. The reason we can’t see such small objects is the ______________ resolution of the human eye.

5. Each cell is a sophisticated machine, finely tuned to carry out a ______________ role within the body.

6. Atoms are linked together into molecules, joined by chemical ______________ that result from forces like the attraction of opposite charges or the sharing of electrons.

7. Demographic ______________ refers to random events that affect a population.

8. Considerable ______________ exists about the identity of the first hominoid.

Translate into Russian

1. The studies concerning active substances secreted by algae are still too recent and too few for us to estimate their importance.

2. In all three devices the elections are moving in a vacuum, sufficiently near to perfect for collisions with gas molecules to be very rare.

3. Since nucleic acid synthesis is necessary for the cell to grow or even to exist the cell has provided itself with more than one pathway for its synthesis in case the others are blocked out.

4. Pyruvate can be oxidized to carbon dioxide and water by these homogenates, via the Krebs cycle; for this to occur it is necessary to mid an adequate supply of 4-carbon acids.

5. The significance of mitosis is that it provides a precise mechanism for this to be accomplished.

6. What the enzyme needs for the reaction to occur are the four desoxyribonucleoside triphosphates plus a small amount of DNA as a primer.

7. For this it is not necessary for the biologist to acquaint himself with the intricacies of wave mechanics.

8. In only a small fraction of the collisions will the molecules come together in the right way for reaction to occur.

9. It is clear that for two molecules to undergo a chemical reaction the molecules must not only collide, but must come together with such an orientation that the bond can be broken.

10. For this to be done the equations for «U» must be developed.

UNIT 8 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 using a dictionary

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…