The cell. Кулагина Ж.Д. - 12 стр.

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      Ex. 17. Read text B and make up a plan of it.

                                        TEXT B
                                    The Cytoplasm
       The remainder of the protoplasm of the cell is known collectively as the
cytoplasm. Various activities of the cell are carried out in the cytoplasm under
the control of the nucleus. Some of them are performed by the cytoplasm as a
whole; others are associated with definite bodies, plastids. Important among
these are the chloroplasts, usually small, roundish bodies present in the cells of
the green tissue of leaves and in certain other parts of the plant exposed to light.
They contain chlorophyll, through the activity of which organic food is
manufactured, chromoplasts which are related closely to chloroplasts are
responsible for most of the red and yellow colours of plants.
       The change from unripe "green" fruit to the ripe condition in many plants
is due to the conversion of chloroplasts into chromoplasts.
       In addition to the plastids there are usually other bodies in the cytoplasm
which are very minute and appear as tiny granules, rods or threads. They are
called mitochondria. These bodies are also parts of the living material of the
cell.
       On the outside of the cytoplasm a delicate plasma membrane is
developed. A similar vacuolar membrane separates cytoplasm and vacuole.
Through one or both of these membranes must pass everything that enters or
leaves the cell. These function as osmotic membranes and thus control the
entrance and exit of water. These membranes are permeable to certain dissolved
substances but impermeable to others and this permeability varies in different
tissues and under different conditions.
       The cytoplasm is not quiet but flows or streams from one part of the cell
to another. In most cells this movement is not conspicuous, but where plastids or
other visible bodies are carried by the streaming, its course becomes easy to
follow. The rate of the flow is affected by environmental conditions, especially
temperature and in general is the most rapid when physiological activity is
highest.

      Ex. 18. Give the content of text B in detail using your plan.

                                    Unit III
                                      Step 1
      Ex. 1. Practise the following for pronunciation:

       bound [baund]                           delicate ['delikit]
       polysaccharide [poli'sækəraid]          electron [e'lektrɔn]