3. Read the text and translate it.

Cells and Their Functions

Look at the cell (Fig. 3-2). The outer covering of the cell is the cell membrane. It is very important in regulating what can enter and leave the cell. The main substance that fills the cell and holds the cell contents is the cytoplasm. This is a colloidal suspension of water, food, minerals, enzymes and other specialized materials.

The cell contents include organelles. All the organelles and their functions in the cell are demonstrated in Table 3—1.

Table 3-1. Cell Structure

Name	Description	Function
Cell membrane	Outer layer of the cell; composed mainly of lipids and proteins	Limits the cell; regulates what enters and leaves the cell
Cytoplasm	Colloidal suspension that fills the cell	Holds cell contents
Nucleus	Large, dark-staining body near the center of the cell; composed of DNA and proteins	Contains the chromosomes with the genes (the hereditary material that directs all cell activities)
Nucleolus	Small body in the nucleus; composed of RNA, DNA, and proteins	Needed for protein manufacture
Endoplasmic reticulum (ER)	Network of membranes in the cytoplasm	Used for storage and transport; holds ribosomes
Ribosomes	Small bodies in the cytoplasm or attached to the ER; composed of RNA and protein	Manufacture proteins
Mitochondria	Large organelles with folded membranes inside	Convert energy from nutrients into ATP
Golgi apparatus	Layers of membranes	Put together special substances such as mucus
Lysosomes	Small sacs of digestive enzymes	Digest substances within the cell
Centrioles	Rod-shaped bodies (usually 2) near the nucleus	Help separate the chromosomes in cell division
Cilia	Short, hairlike projections from the cell	Create movement around the cell
Flagellum	Long, whiplike extension from the cell	Moves the cell

Protein plays a very important part in the organism and its production takes place in the cell. There are two nucleic acids in the cytoplasm and nucleus, which are important in protein production:

- deoxyribonucleic acid or DNA is mostly found in the nucleus and makes up chromosomes. DNA is double stranded;

- ribonucleic acid or RNA is single stranded, it is located in the cytoplasm.

Cell reproduction occurs by the dividing process called mitosis. In this process each original parent cell divides to form two identical daughter cells.

Various physical processes take place in the cell:

1. diffusion - molecules move from an area of higher concentration to an area of lower concentration;

2. osmosis - diffusion of water through the semipermeable membrane;

3. filtration - movement of materials through the cell membrane under mechanical force;

4. active transport - movement of molecules from an area of lower concentration to an area of higher concentration;

5. phagocytosis"- engulfing of large particules by the cell membrane;

6) pinocytosis - intake of droplets of fluid; the word pinocytosis means "cell drinking". Each of these processes is necessary for the functioning of the cells.

Cells develop different forms, these forms of the same kind congregate to form one of the basic tissues. These tissues, in turn, become specialized organs. So, every cell and formation of cells has its purpose.

But sometimes in the DNA or genetic material a mutation or change occurs. If such a cell doesn't die naturally or get destroyed by the immune system, it may begin to multiply out of control and spread to other tissues, producing cancer. Cancer cells form tumors, which interfere with normal functions, crowding out normal cells and robbing them of nutrients.

Because cancer may take a long period to develop, it is often difficult to identify its causes. Certain factors increase the changes of developing the disease and are considered risk factors.

Risk factors include heredity, carcinogens or chemicals (in food, environment, drugs), ionising radiation (X-rays, ultraviolet rays), physical irritation (intake of hot food), diet (high in fats), viruses.

4. Look at Table 3-1, name the components of the cell, describe all of them.

5. Translate the functions of each organelle of the cell (from Table 3-1).

6. Tell about cell division. Use Figure 3-3.

7. Find English equivalents in the text.

Основна одиниця життя, обмін речовин, невидимий для неозброєного ока, однолінзовий мікроскоп, ДНК, РНК, підтримує елементи клітини в цитоплазмі, мінерали і ферменти, утворення білка, процес поділу клітин - мітоз, фізичні процеси, рух матеріалів через клітинну мембрану, поглинання великих часток, клітина п'є, клітина розвиває різні форми, має свої цілі, руйнується імунною системою, переходить на інші органи, утворює пухлини, тривалий період розвитку, фактори ризику.