Fill in the gaps with the following words and word combinations. properties / compounds / melting points / deviation / tension / floats / density

properties / compounds / melting points / deviation / tension / floats / density

1. Fats made from polyunsaturated fatty acids have low ______________ because their fatty acid chains bend at the double bonds, preventing the fat molecules from aligning closely with one another.

2. In a human, if the body temperature exceeds the set point of 37°C, sensors in a part of the brain detect this ______________.

3. Each DNA strand ______________ or sinks in the gradient until it reaches the position where its ______________ exactly matches the density of the cesium there.

4. Polar water molecules are attracted to ions and polar ______________, making them soluble.

5. Water forms an abundance of hydrogen bonds, which are responsible for many of its important physical ______________.

6. The cohesion of liquid water is also responsible for its surface ______________.

Translate into Russian

1. Whether there is really an exchange with the host chromosome or with some prophages on that chromosome is a problem for the future.

2. Whether the structure of these nuclei involves other constituents than DNA and whether their mode of division is more complex than that of DNA itself are questions to be answered in the future.

3. We can ask now whether the bacterial zygote, which is clearly partial, undergoes something akin to meiosis in the production of its haploid progeny among which the recombinants are found.

4. We may ask whether it is possible in this case to be sure that the genetic subunits in this complex form one large functional gene which can operate only when all of its parts are normal.

5. We must question whether it is true that the molecules of a sufficiently purified protein preparation all carry exactly the same amino acid sequences.

6. The controversy as to whether this was indeed a true description of the movement and interaction of the filaments during contraction arose from the difficulty of accurately measuring changes in the lengths of the bands in polarized light and interference microscope studies, since these changes lie at the limit of light microscope resolution.

7. In these sections on the permeability of membranes we have tried to indicate whether any particular mechanism is found in only certain cells or in other cell types also.

8. For a long time it remained undecided whether the genetic information resided in the protein in the DNA component.

9. All life is connected with motion of some sort, whether it is the contraction of muscle cells, the flow of the amoeba, the cyclosis of the protoplasm in a plant cell, or the movement of chromosomes.

10. We do not know whether this is a physiological necessity or an evolutionary consequence of natural selection.

11. Whether this striking parallelism is coincidental or a form of biological conservation of the chemical composition of the surroundings present when life first originated is as yet only a matter of speculation.

12. The state of reduction of these coenzymes could very well influence the fate of fat in the cell whether it is to be oxidized for energy or whether it will go to from the higher fatty acids.

13. Whether life started spontaneously from nonliving matter, or whether it came to our planet in the form of spores seeded throughout the universe by distant solar systems, we don't know.

14. It does not seem possible at the moment to say whether the mechanism for UV induction involves two hits in the same target, or whether it requires one hit in two different targets.

UNIT 17 Water Potential and Water Content

Two types of variables are required to describe the state of matter or energy. One describes the amount, while the other describes the quality or intensity. For example, the thermal state of a substance is described in terms of its heat content and its temperature. While the two variables are related (the higher the temperature of a substance, the higher the heat content), they are not equivalent. The heat content depends on the mass, specific heat, and temperature of the substance, and gives no indication of which direction heat will flow if the object is placed in contact with another object. The temperature of an object specifies the intensity or quality of the heat, and temperature differences relate directly to direction and rate of heat flow.

Variables like temperature, which describe intensity of quality are called intensive variables, while variables describing amount are called extensive variables. Temperature is intensive while heat is extensive. To refer to thermal time as "heat units" is a confusion of intensive and extensive variables.

Describing the state of water in a system also requires the use of intensive and extensive variables. The extensive variable is familiar to most, and is called the water content. The intensive variable, called the water potential, is less familiar. Like temperature, it determines the direction and rate of water flow. As with temperature, there is often a relationship between the water content and the water potential of a substance, though it is always much more complicated than is the case for temperature. The important thing to realize is that water in soil, or in the tissues of living things, is not like the water in a glass. It is bound by the tissue or soil matrix, diluted by solutes, and sometimes is under pressure or tension. Its energy state is therefore quite different from that of water in a glass.

The water content is simply the ratio of the volume of water in a material to its total volume, or the ratio of mass of water to dry or wet mass of the material. Different bases are used as the standard in different disciplines, and all are called water content, so it is easy to make mistakes if one is not careful.

Define the following words and word combinations

The intensive variable, a solute, the soil matrix, the extensive variable, the ratio

Complete the sentences

1. The thermal state of a substance is described…
2. The temperature of an object…
3. Temperature is intensive…
4. To refer to thermal time as "heat units"...
5. The important thing to realize is…
6. Different bases are used as…