LESSON 2

I) Learn to pronounce, write and read English words and medical terms and memorize their Russian equivalents

1. Write in letters

[mt] [sjutbl] [invairnmnt] [neibri] [mainju:t] [saitplzm] [p:mibl] [maitukndri] [nju:kliuls] [kwliti] [krumsum] [maittik] [maitusis] [krumtid] [maiusis] [d:t]

2. Write the following words in transcription

anaphase, chloroplast, deoxyribonucleic acid, endoplasm, lysosome, nucleoprotein, organelle, prophase, ribosome, nucleus

3. Read the following terms

a) erythrocyte, gene, granule, kernel, metaphase, nutrient, telophase, membrane, granule, protein, semipermeable

b) Golgi apparatus, ribonucleic acid, endoplasmic reticulum, nucleic acid, electron microscope, reduction division

II. Text study

4. Read the text, translate it consulting dictionary, if necessary, and answer the questions after the text

The cell

The cell is the smallest unit of living matter capable of independent life. Its main function is to preserve a suitable environment for itself and for neighbouring cells. It is a minute, mainly microscopic, mass of cytoplasm bounded by a semipermeable container, the cell membrane.

There are non-nucleated cells, such as the erythrocytes, but most cells have one or more nuclei. These are dense kernels which direct the activity of the rest of the cell.

Under a high-power microscope, the cell reveals a complex structure with a number of specialized parts called organelles. They are so tiny that we need an electron microscope to observe them.

The most important organelles include mitochondria – in which combustion of nutrients provides energy to keep the cell alive, ribosomes – which have the vital function of synthetizing proteins, Golgi apparatus – responsible for the elaboration and secretion of cell products, lysosomes, endoplasmic reticulum, chloroplasts etc.

The nucleus itself is a complex structure separated from the cytoplasm by an enclosing membrane, the nuclear envelope. There are one or more nucleoli and a number of granules. The nucleus as a whole is composed mainly of nucleoprotein. The chemical composition of nucleoprotein is important because it determines what proteins the cell can produce. This is the major factor in determining the biological properties of the cell as a whole.

The granules contain a quantity of nucleic acid, i.e. the DNA and RNA. The body contains thousands of different kinds of proteins each of which is determined by its own unit of DNA called a gene. Each of the genes governs the synthesis of one protein.

The outstanding quality of DNA is that it can make an exact copy of itself by splitting into two halves. Before a cell divides, its DNA is organized into paired structures called chromosomes. A chromosome is a collection of hundreds of genes.

The mitotic division of a cell takes place in four phases:

prophase — this is the initial part of mitosis, in which chromosomes are con­densed from the resting form of a multitude of genes and split into paired chromatids. The spindle and aster are formed, and this is followed by the alignment of the double chromosomes across the centre of the spindle;

metaphase — is marked by the complete separation of each of the 23 pairs of chromosomes;

anaphase — the mitotic process reaches the point when chromosome halves move towards the pole of the spindle;

telophase — is the final stage of cell division. It is marked by the appearance of two daughter cells.

There is no splitting of the chromosomes when the germ cells (the ovum and the sperm) are formed. This process is called meiosis or reduction division. Instead, only one member of a pair of chromosomes goes to a germ cell so that there are 23 single chromosomes. When the ovum is fertilized, new pairs are made with one member form either parent.

5. Answer the following questions

1. What is a cell? 2. What does a cell look like? 3. What are the main parts of the cell? 4. What will a high-power microscope reveal? 5. What kind of process takes place inside mitochondria? 6. In which part of the cell are proteins synthetized? 7. What is the Golgi apparatus responsible for? 8. What is the nucleus mainly composed of? 9. Which are the principal nucleic acids? 10. What is the characteristic feature of DNA? 11. What is the difference between a chromosome and a gene? 12. Which are the four phases of mitotic division? 13. What kind of activity is characteristic of the prophase? 14. What goes on during meiosis? 15. What will have happened by the time metaphase can begin?