8. Organic compounds and life

Many chemical compounds besides water are needed for life to exist. The most important are organic compounds .Chemically speaking organic compounds are carbon compounds in which the carbon atoms are combined with hydrogen and usually oxygen .Organic compounds also frequently contain nitrogen, sulfur, or phosphorus .A few carbon compounds have never been included with organic compounds: carbon dioxide (C O ),carbon monoxide (C O),and carbonic acid (H C O ).

The name «organic» was coined long ago when it was thought these compounds could be formed only by living cells .Since then millions of different organic compounds have been synthesized in the laboratory. There is no longer any reason to call these compounds «organic»,but the name is so well established that it is widely used to describe nearly all carbon compounds ,essential for life or not . Carbon can combine in long chains that form the backbone of large ,complex molecules or macromolecules. The backbone of carbon atoms is called the carbon skeleton. Other atoms and molecules can attach to the carbon skeleton ,giving each macromolecule a particular structure and, therefore ,a particular function .The following sections of the chapter discuss the characteristics of the four most important classes of macromolecules-carbohydrates, lipids ,proteins, and nucleic acids.

Exercise 10. Master the active vocabulary:

compound[´kompand] - состав, соединение

hydrogen[´haidr∂d(∂)n] - водород

oxygen [´oksid (∂)n ] - кислород

nitrogen [´naitr∂d (∂)n] - азот

carbon[´ka:b(∂)n] - углерод

Exercise 11. Answer the questions:

1) What are organic compounds?

2) What elements do organic compounds contain?

3) When was the name «organic» coined?

4. What is a carbon skeleton?

Exercise 12. Find English equivalents for:

органические соединения; существовать; углеродные соединения; создавать (новые слова, выражения); основа.

Exercise 13. Read the text.

Carbohydrates

All known types of living cells contain carbohydrates (KAR both HY drayts; carbo = carbon, hydrate =water). In addition to carbon atoms, carbohydrates contain hydrogen and oxygen atoms in the same two-to-one ratio as water. The simplest carbohydrates are single sugars called monosaccharides (MON oh SAK uh rydz). Most organisms readily use the monosaccharide glucose (also called blood sugar) as a source of energy.

(a) In solution, glucose, a 6-carbon sugar, can exist in two forms: a straight chain and a ring form. The ring form, in which 5 carbon atoms and an oxygen atom form a closed ring, is by far the most abundant. (b) The two forms of glucose-6-phosphate.

Biologically important sugars often have a phosphate group attached to the carbon skeleton and are called sugar phosphates. The phosphate group, which is composed of an atom of phosphorus and three atoms of oxygen , is shown as P when attached to a carbon skeleton. For example , glucose-6-phosphate,which has important roles in the cells, has a phosphate group attached to its sixth carbon atom.

Several glucose molecules may bond together to build complex carbohydrates called polysaccharides(POL ee SAK uh rydz ).Starch and cellulose are the complex are the complex carbohydrates commonly formed by plants. Starch is an energy-storage and carbon-reserve compound in many plants and is an important food source for humans .The rigid walls surrounding plant cells contain cellulose, an important part of wood and cotton fibers .The human liver and muscles store carbohydrates in the form of glycogen (GLY ko jen ) ,also called animal starch .Molecules of starch, cellulose , and glycogen consist of thousands of glucose units and have no fixed size.

Exercise 14. Master the active vocabulary:

carbo-hydrate [ka:b∂´haidreit] - углевод

glucose [´glu:k∂ s] - глюкоза

phosphate [´fosfeit ] - фосфат

phosphorus [´fosf(∂)r∂s ] - фосфор

starch [sta:t ] - крахмал

cellulose [´selj l∂ z ] - целлюлоза, клетчатка

fiber [´faib∂] - волокно, фибра

Exercise 15. Answer the questions:

1) What atoms do carbohydrates contain?

2) What do most organisms use as a source of energy?

3) What are sugar phosphates?

4) What is starch?

5) What is cellulose?

Exercise 16. Change the order of ideas to that actually used by the author:

1. The rigid walls surrounding plant cells contain cellulose,an important part of wood and cotton fibers.

2. The simplest carbohydrates are single sugars called monosaccharides.

3. Several glucose molecules may bond together to build complex carbohydrates called polysaccharides.

4. All known types of living cells contain carbohydrates.

5. Starch and cellulose are the complex carbohydrates commonly formed by plants.

6. Molecules of starch, cellulose, and glycogen consist of thousands of glucose units and have no fixed size.

CONTENTS

Part 1. Знакомство. 3

Part 2. Путешествия. Различные виды путешествий и их характеристики. 12

Part 3. У врача. Медицинское обслуживание. 33

Part 4. Моя страна. Мой город. Достопримечательности. 43

Part 5. Страны изучаемого языка (Великобритания, США, Австралия, Новая Зеландия): географические, политические и культурные аспекты. 58

Part 6. Наш университет. Высшее образование в России. 79

Part 7. Высшее образование в стране изучаемого языка. Ведущие мировые университеты. 86

Part 8. Покупки. В магазине. 108

Part 9. Война и мир. Угроза терроризма. 119

Part 10. Страны третьего мира. Проблемы миграции. 126

Part 11. Информатизация общества. 151

Part 12. Область моих научных интересов. 169

Part 13. Современные достижения науки. Перспективы развития науки. 194

Part 14. Выдающиеся учёные прошлого. 216

Part 15.Экологические проблемы Астраханского региона, России и мира в целом. 232

Part 16.Научно-технический прогресс. История науки. Знаменательные научные открытия прошлого. 242

253