Practice in word-formation and vocabulary

Exercise 1.Match the following adjectives with the negative prefixes UN, NON, IN. The first has been done for you.

- in organic (substance)

-animate (matter)

-living (body)

-natural (behavior)

-separable (union)

-mistakable (signs of life)

 

Exercise 2.Point out which of the words with the same root belong to N (noun), V (verb), Adj (adjective), Adv (adverb) classes. Be guided by suffixes as structural signals. Translate these words into Russian.

variety - vary - variation - various

responsiveness - response - respond - responsive

nature - natural - naturally

activity - active - actively - activate - activeness

reproduction - reproductive - reproduce - reproducible

distinguish - distinguishable - distinguished – distinguishing

 

Exercise 3. Give Russian equivalents to the following word combinations. In case of difficulty turn to the translations given below.

Variety of life, a rich variety of insects, members of a species vary, to observe variations, to distinguish between living and non-living bodies, the distinction is not difficult to observe, the distinct activities of living bodies, distinct species

of plants and animals, hardly distinguishable plants, all typical organisms are responsive, inanimate responses are simple reactions, responsiveness of organisms, organisms respond to light and food.

 

Способность организмов к биологической реакции, наблюдать изменения, основные отчетливые проявления жизнедеятельности организмов, многочисленные виды насекомых, едва отличимые друг от друга растения, разнообразие жизни, проводить различие между живым и неживым в природе, все типичные организмы реагируют на раздражение, члены вида изменяются, этот отличительный признак не трудно заметить, неживые тела характеризуются простыми реакциями, организмы реагирует на свет и пищу, разные виды растений и животных.

 

Exercise 4.Note some cases of word-formation (the initial word comes from TEXT A). Translate them into Russian.

1. Develop (v) ---- development (n) ---- developmental (adj)

2. Distinguishable (adj) ---- distinguish (v) ---- distinguished (adj)

3. Determinant (adj, n) ----determine (v) ----determinative (n, adj)

4. Hereditary (adj) ----heredity (n) ----inherit (v) ----inheritance (n)

 

 

UNIT 4

 

PRE-TEXT TASKS

Study carefully the list of phrases and their Russian equivalents to avoid any difficulty in working through text A.

	at least	по крайней мере
	whatever	какие бы
	elongate and branched	вытянутые и разветвленные
	regardless of their shape	независимо от их формы
	tend to become rounded into drop-like spheres	имеют тенденцию к образованию округлой, каплеобразной формы
	ranges from... to	колеблется в пределах от... до
	most... protein synthesis is believed to take place...	считают, что синтез белков в основном происходит в...
	staining	окрашивание
	takes a deeper colour	придает более темную окраску
	has sufficient resolution	имеет достаточную разрешающую способность (о микроскопе)
	protects against extremes of temperature	защищает от экстремальных температур
	sequences of amino acids	последовательности аминокислот
	maintains a supply of amino acids	сохраняет запас аминокислот
	particular properties	определенные свойства
	are arranged in the chain	расположены в цепочке
	they make up the giant molecules	они образуют гигантские молекулы
	strands	Спирально закрученные нити / ДНК /
	... are coiled round each other	обвивают друг друга
	the bases can only be paired in two ways	/азотистые/ основания соединяются попарно только двумя способами
	enzyme transcriptase	фермент транскриптаза
	messenger RNA	информационная РНК

 

Т Е XT А

The structure of the cell

What we commonly think of as cells consist at least of a mass of protoplasm surrounded by a membrane and containing a nucleus. But a cell, whatever its morphological peculiarities may be, is an integrated and continuously changing system. In plants and animals there are many different kinds of cells with many specialized functions. The amoeba and the bacterium are among the smallest unicellular organisms. The largest single cells are the egg cells of birds. In man, a multicellular organism, there are thousands of millions of cells, and many of these are renewing themselves all the time.

The form of each cell depends on performing a particular function. Nerve cells, for example, are elongate and branched, a form that enables the cells to conduct impulses from one part of the body to another. Regardless of their shape all cells tend to become rounded into droplike spheres, as protoplasm is, essentially, a liquid system.

The nucleus of a cell, separated by a delicate nuclear membrane from the cytoplasm, is derived from a mother cell by mitosis or by meiosis. The size of the nucleus ranges from a small fraction to almost the whole cell volume. The nucleus contains most of the DNA together with other materials. The nucleus is essential to the cell for it to continue living, without it the cytoplasm soon dies.

The cytoplasm is not just a simple fluid, it is highly heterogeneous; in it are situated various structures, called organelles,such as ribosomes and mitochondria. Most, probably all, protein synthesis is believed to take place in ribosomes. The mitochondria contain phosphates and numerous enzymes which vary in different tissues, their function is cellular respiration and the release of chemical energy. In plants, of course, there are the plastids, carriers of the chlorophyll by which the energy of sunlight is made to synthesize organic compounds from carbon dioxide.

One must know that when a researcher begins to study cells he may use various techniques and methods. One of them is staining. The living cell nuclear and cytoplasmic parts are known to be transparent and colorless. When a cell is stained, the nucleus becomes plainly visible. It takes a deeper color8 than the cytoplasm, thus enabling the researcher to examine the cell under the light microscope. Electron microscopes have now replaced all others as the means for discovering and studying the details of cellular structure. The electron microscope has sufficient resolution to show the protein and other molecules.

All the substances present in protoplasm are known to fall into two great classes: inorganic and organic substances. The most important inorganic compound in protoplasm is water. The movement of substances in or out of cells is dependent on their being dissolved in water. Water protects against extremes of temperature. Its ability to conduct heat well is useful in equalizing temperatures throughout a living body.

Organic compounds occur only in living bodies or in their products or remains. The element carbon (С) is present in all organic compounds. Organic compounds are somewhat unique since the atoms of carbon can occur as chains or join to form rings. The organic compounds are known to be divided into three main classes - the carbohydrates, the lipids and the proteins.

Proteins are all-important structural components in every cell amounting to 15% in protoplasm. A protein is built of sequences of amino acids linked together by means of peptide bonds to form a chain. Each amino acid is composed of the carboxyl group (-COOH) and the amino acid group (-NHg), attached to the carbon atom next to the carboxyl group. The general formula is RCHC(NH2)COOH where R is a variable grouping of atoms.

Every organism maintains a supply of amino acids in a definite proportion of the 20 common and 2 rare amino acids, peculiar to each species of organism. The particular properties of the protein depend upon the order in which the 20 amino acids are arranged and repeated in the chain. One of the simplest of the proteins is insulin. Its molecule contains 51 amino acids representing 15 different kinds.

Finally, there are the instructional or information-carrying molecules in cells, nucleic acids. These are composed of five main nitrogen-containing purine and pyrimidine bases, ADENINE (A), GUANINE (G), CYTOSINE (C), THYMINE (T) and URACIL (U), combined with phosphoric acid and ribose or the related deoxyribose. They make up the giant molecules of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) which are responsible for arranging the amino acids in proper sequences in the proteins.

On the basis of results of X-ray crystallography on DNA, James Watson and Fransis Crick proposed in 1953 their now-famous model, which shows DNA as composed of two strands. Usually two strands are coiled round each other in the form of a double spiral, with the strands connected to each other through a pair of bases. The bases can only be paired in two ways. Adenine pairs with thymine or uracil, and cytosine pairs with guanine.

DNA is found only in the chromosomes of plants and animals and the corresponding structures in bacteria and viruses. RNA is found in the nuclei, the ribosomes and the cytoplasm of all cells of all organisms. A single strand of RNA produced from a length of DNA (a citron) by the enzyme transcriptases called messenger RNA (mRNA). A molecule of mRNA contains the genetic code to be translated into a particular polypeptide molecule. The sequence of amino acids in a protein is determined by the sequence of the nucleotides in a molecule of messenger RNA.

Enormous advances have been made in the last twenty years in a giving precise chemical knowledge on these matters. We expect the researchers to make new discoveries in the structures and chemistry of the cell.

 

NOTES

1. The element "proto" in the words "protoplasm", "protein" comes from the Greek word "protos"→"first".

2. unicellular→"unus"(Latin) →"one" + cell (Latin) → “small room"

3. multicellular →"multus"(Latin) →"much/many" + cell(Lat.) → "small room"

4. heterogeneous→"hetero"(Greek) →"other" +"genos" (Greek) → "kind"

 

singular:	plural:
nucleus	nuclei
mitochondrion	mitochondria

 

COMPREHENSION CHECK

Exercise 1.Join the suitable word or phrase, marked (A),(B),(C), that best completes the sentence.

1. Different kinds of cells...

a. are found in the bacterium.

b. perform specialized functions.

c. have only protoplasm surrounded by a membrane.

2. The nucleus of a cell is separated...

a. by a delicate membrane.

b. by meiosis.

c. by drop like spheres.

3. It is well known that the cytoplasm...

a. is composed of different kinds of material.

b. is transparent when it is stained.

4. In plant cells organic compounds...

a. are not hard to see under the light microscope.

b. become plainly visible when a cell is stained.

c. are synthesized from carbon dioxide and water using sunlight energy.

5. The most important constituents of the nuclear membrane are...

a. proteins

b. proteins and lipids.

c. plastids.

6. The particular properties of the protein depend upon...

a. the order in which the amino acids are arranged.

b. the number of carboxyl groups.

c. the two strands of DNA which are coiled round each other.

7. RNA is found...

a. in membranes.

b. in the nuclei and the cytoplasm.

c. in the chromosomes of plants and animals.