The cell. Кулагина Ж.Д. - 35 стр.

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      Ex. 7. Define the tense and voice of the following sentences.

1. Large plants and large animals have large numbers of cells rather than large
cells. 2. In the long course of their evolution birds and mammals have evolved
the faculty to maintain the intensity of their metabolism. 3. The nucleus has been
removed from the cell artificially. 4. Investigations dealing with the structure
and activity of protoplasm have been conducted. 5. At this stage the cells are
already being prepared for mitosis. 6. Thousands of seals are dying on the
beaches of Northern Europe. 7. The cell sap shouldn’t be regarded as a living
material. 8. In the process of metabolism some substances should break down
either because they no longer serve a useful purpose or because they are used as
a source of energy. 9. Zoology may be divided into two subsciences. 10. Some
of the chemical changes lead to the formation of the complex organic
substances. 11. The cell membrane and the cell wall play an important part in
protection of the cell against injury. 12. The specific features of metabolism in
some plants and animals depend on a number of factors and are quite individual.

                                      Step 2
     Ex. 8. Listen to the recording of text A and give a definition to the term
“metabolism”.
                                     Text A
       All living organisms, however great the difference between them is,
possess a number of common features, one of which is the presence of protein
and nucleic acids, and another the property of exchanging matter.
       A constant exchange of substances between an organism and its
environment is an indispensable condition of vital activity. Every cell, every part
of an organism and the organism as a whole are in a constant state of metabolic
exchange.
       By metabolism is meant all the chemical changes, including all of the
chemical processes which take place in a living thing. Some of these changes
lead to the formation of the complex organic substances which actually make up
the living protoplasm or are stored in it. These substances are carbohydrates,
fats, and proteins. Other processes lead to breaking down of some substances
either because they no longer serve a useful purpose or because, like sugar, they
are used as a source of energy.
       So metabolism is a double process consisting of assimilation and
disassimilation.

      Ex. 9. Reproduce text A, using the phrases given below as a plan.

     1.   to possess common features;