Fill in the gaps with the following words and word combinations. range / urine / fluid / approaches / transpiration / turgor pressure / equal to / variation / saturated

range / urine / fluid / approaches / transpiration / turgor pressure / equal to / variation / saturated

 

1. ______________ in the environment, either spatial or temporal, can be used to explain how some polymorphisms arise.

2. As blood plasma passes through capillaries, the pressure of the blood forces some of this ______________ out of the capillary walls.

3. In some reptiles and birds, additional water from either the feces or ______________ may be absorbed in the cloaca before the products are expelled from the body.

4. On the surface of leaves and other organs, water loss called ______________ creates a negative pressure.

5. Most enzymes function within a very narrow ______________ of physical parameters.

6. Atmospheric air is rarely ______________ with water vapor, except immediately after a rainstorm.

7. Once each month, the moon ______________ closer to the earth than usual, and when it does, its increased gravitational attraction causes somewhat higher tides.

8. The atomic mass of an atom is ______________ the sum of the masses of its protons and neutrons.

9. The ______________, which is a physical pressure that results as water enters the cell vacuoles, is referred to as pressure potential.

 

Translate into Russian

1. Ideally, one would like to determine the actual linear order of bases in a nucleic acid molecule, but, if each cell contains a great variety of different types of molecules, the first problem is that of isolating one kind of molecule from the others.

2. One may ask whether transformation experiments exclude the possibility that DNA acts not as hereditary material but as a mutagenic agent.

3. When a cell is transformed from streptomycin sensitivity to resistance, one may inquire whether the transformed cells now contain only the new determinant, or whether they contain both the old and the new.

4. These experimental results lead one to view a hereditary determinant or gene as part of a DNA molecule capable of assuming at least two alternative states, only one of which can be present at a time.

5. Although the RNA infection experiment demonstrates that hereditary information can be carried by RNA alone one may still ask whether the protein moiety may also carry information.

6. One may conclude from these experiments that two classes of macro-molecules, the ribonucleic acids and the deoxyribonucleic acids, carry hereditary information in particular systems.

7. One may postulate RNA as the carrier of this type of hereditary information, but there is no direct confirmation of this hypothesis as yet.

8. How do genes act? When one observes the extraordinary precision of heredity — the extent to which progeny resemble their parents, embryos develop identically, species differ consistently— one feels convinced that the directing role of the hereditary determinants must be pervasive, encompassing a great variety of activity.

9. If one considers the problem of gene action in a single-celled organism, and further simplifies matters by surveying the effects of known gene mutation, the picture becomes somewhat less blurred.

10. Judging from the similarity in chromosome morphology and in genetic linkage from strain to strain of most species, one might infer that the chromosome is an exceedingly stable structure.

11. When these chromosomes pair at meiosis, one finds the kind of configuration shown diagrammatically in Figure 4.2 b.

12. If one explores the cell surface in greater detail one discovers that some of the invaginations are not delimited by a vesicle but instead lead right into the depth of the cell.

13. One could predict that reactions 3 and 4 should be reversible involving as they do compounds of approximately equal energy content.

14. If we go through the list of problems enumerated above, we will find that the ones with which biochemistry was successful were problems of structure, or changes of structure.

15. Under the microscope one finds featherlike crystals running in different directions.

16. One may wonder why these ions dissolve, dissociate, and whether some other parameter has not been overlooked.

17. The tube containing KSCN will be darker brown than the one with KI.

18. The concept of the equivalent pore serves to provide a physical model which enables one to predict the behaviour of the membrane with respect to the passage of molecules other than water.

19. It is not possible to say whether lysogenicity is a universal property of bacteria or not, but it is certainly a very general one.

20. One may utilize ionizing radiations to provoke induction and then study the interaction of virus and host.

21. When one irradiates a growing population of lysogenic bacteria, the cells enlarge without dividing, causing the opacity to increase at normal rate.

22. Such differences between X-rays and UV are not uncommon. One may explain them by the very low quantum yield in case of UV.

23. Doermann has found that if one adds cyanide to a culture of E coli В infected with phage T 2, virus synthesis is stopped, but lysis occurs nevertheless.

24. The theoretical relationship is most probably an exponential one, but at such low frequency of induced bacteria, the exponential curve cannot be distinguished from a linear one.

 

 

UNIT 19 Structure Formation of Biomacromolecules

Investigations of the 3-dimensional structure of biological macromolecules, their genetic coding, and especially the processes of self-assembling of these structures, are the main problems of molecular biophysics. There is no doubt that the total information on the stearic structure of proteins is stored in its primary structure, i.e. in the sequence of the amino acids. The question arises as to how one can decode the 3-dimensional structure of a protein, reading its amino acid sequence and furthermore, how the process of self-assembly, which leads spontaneously and reversibly to this genetically predicted protein structure, really works?

The proteins are composed of α-L-amino acids which are connected to each other, forming long chains. In these connections the carboxyl groups of the α - S - Atoms are condensed with the amino group of the following monomer, splitting up a molecule of water.

These molecular chains have a high degree of flexibility. During Brownian movement, interconnections of various parts of these chains are possible. This occurs mostly by hydrogen bonds connecting atoms of two peptide bonds, or atoms of a peptide bond with those of a side chain of an amino acid, or finally of two side chains together. Covalent bonds between side chains are also possible. This is mostly done by disulfide bridges between the SH-groups of cysteins. Electrostatic and hydrophobic interactions also take place.

Let us start to consider possible mechanisms of self-assembly, hypothesizing that the molecule will move stochastically, reversibly connecting and disconnecting bridges with monomers of its own chain. This proceeds as long as the polypeptide chain does not become a structure of minimal conformational energy, which will be identical with the active structure of the natural protein.

 

Define the following words using a dictionary

 

Biomacromolecules, a prerequisite, to condense, to split, cystein

 

Complete the sentences

1. There is no doubt that…

2. The question arises as to how one can decode…

3. During Brownian movement,…

4. This occurs mostly by…

5. Let us start to consider possible mechanisms of self-assembly…

6. This proceeds as long as…