Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.

Категории

Биология Exercises
просмотров - 584

1. Complete the sentences with the verb in the correct form: Present Simple, Present Perfect, Past Simple Tense.

INTERFERON

Virus diseases …..( plague) mankind for thousands of years, but, until recently, no medical treatment for them …..( be) available. Although the use of vaccines almost …..(eliminate) several major viral diseases, such as polio and smallpox, medical research …..( provide) no means for treating virus diseases already established in the body. No drugs …..( be) made available for combating viruses even though drugs such as penicillin have been used so effectively against bacterial infections.

Ever since 1957, when interferon was discovered, there …..( be) the hope that this natural antiviral substance produced by cells might provide an effective treatment for a broad range of virus diseases that are not subject to control by antibiotics. Not for the first time firm evidence has been presented that an animal's body can be stimulated to produce enough interferon to cure an acute infection. An eye disease in rabbits was treated by administering an agent that …..(raise) the animals' interferon level and …..(clear) up the infection.

Interferon …(be) a protein, produced by cells under virus attack, that in turn apparently … (give) rise to a factor that limits the spread of the virus. The interferon system has been demonstrated in the laboratory and in human beings, but the body's own system often …..( not produce) enough interferon to overcome an established infection. Treatment with prepared interferon can prevent many viral infections and …..(have) some protective effect when it is given after inoculation with a virus and before the onset of disease, but it is hard to accumulate enough prepared interferon to treat an established infection.

Many workers in virology, biochemistry, and molecular biology …..(study) interferon, and out of this research …..(come) the rationale for an entirely new approach to the treatment of viral disease-induction of the synthesis of interferon in the body in order to stimulate the cell's natural defence mechanism.

2. Complete the sentences with the verb in the correct form: Present Simple, Present Perfect Continuous, Present Perfect Tense.

1) Men …..( dig) up fossils for centuries, but it is only in the last two hundred years that they generally ….. (recognize) as the remains of living things.

2) If disturbed, earwigs run away very quickly, but if they …..( hide) in a lettuce, they cling on tenaciously and they manage to keep afloat in water for quite a while.

3) A smoke-cloud darkened the sky and the earth …..( tumble) for days.

4) The seals …..( breathe) through tiny cracks in the ice. These conclusions are substantiated by Arctic explorers and research workers who …..(study) the northern hunting grounds.

5) Mankind ….. (eat) corn for so many hundreds of years that today we ….. (think) of it as just another fine vegetable.


Читайте также


  • - Exercises

    1. Complete the sentences with the verb in the correct form: Present Simple, Future Simple Tenses. Watch tadpoles grow 16) If you look in a pond, you ..... (see) in a shallow water great lumps of jelly. That ..... (be) frog's spawn. Mother frog ..... (lay) up to 800 eggs. Don't think she ..... ( take) care of them. She ...... ( leave) them, floating on the surface to look after themselves as soon as the eggs are laid. Then in a few days if you look at an egg you ..... ( notice) a black spot,... [читать подробенее]


  • - Exercises

    1. Put in a\an or the where necessary. ..…Britain, in which ... fifty million people live and work, is,.. land of... great variety. There are many large cities, but they are surrounded with ... quiet countryside. There are ... plains in ... east, hills in... center and south-west, and ... mountains in ... north. Some parts of ... country are almost without ... trees while others have ... great forests, ... south is ... land of... rivers, but Scotland is... land of ... lakes. One of ...... [читать подробенее]


  • - Summarizing Exercises

    Exercise 296. Choose the appropriate variant. 1. … get up after the operation yet? a) Is he allowed to b) Can he c) Might he 2. The trip by train lasted for a week! They … exhausted by now! a) had better b) can c) must 3. Percy … watered my cyclamen, look, it’s dying. a) didn’t have to b) needn’t have c) might have 4. You … be at the airport 2 hours ahead of time, otherwise you will have problems with registration. a) are to b) have to c) must 5. I … hear... [читать подробенее]


  • - VOCABULARY EXERCISES

    Exercises to the lead-in section and the text (Upstream Intermediate, pp.6 – 7) I. Use the dictionary and see the pictures on the next page to find out the differences between the following types of buildings. Get ready to explain them to the class: 1. a bungalow 2. a terraced house BrE / row house AmE 3. a semi-detached house BrE / duplex AmE 4. a detached house 5. a block of flats BrE / an apartment building AmE 6. a cottage 7. a ranch house II. Learn the pronunciation... [читать подробенее]


  • - VII. Speak on the Soviet Union's achievements in different spheres of life. Make use of the text and the additional passages given in Exercises V, VI. 4 страница

    work n работа, труд manual (intellectual) work физический (умственный) труд to erase distinctions between manual and intellectual work стереть различия между физическим и умственным трудом Z zone n зона; пояс a time zone часовой пояс a climatic zone климатический пояс the Non-Black Earth Zone Нечерноземная... [читать подробенее]


  • - VII. Speak on the Soviet Union's achievements in different spheres of life. Make use of the text and the additional passages given in Exercises V, VI. 3 страница

    C capacity n мощность annual capacity to have a capacity (with a capacity) of 2,000,000 kilowatts годовая производительность иметь мощность (мощностью) в 2 000 000 киловатт. (public) catering n общественное питание a catering institution/establishment предприятие общественного питания census n перепись населения to take... [читать подробенее]


  • - VII. Speak on the Soviet Union's achievements in different spheres of life. Make use of the text and the additional passages given in Exercises V, VI. 2 страница

    She was sent to the neighbouring republic of Uzbekistan to continue her education. There, in Tashkent, under a decree signed by Lenin, the first state university in Central Asia had been opened in 1920. Tajibayeva joined its geological department. She was in Tashkent when the Great Patriotic War of 1941-1945 broke out. She attended lectures in the morning and nursed the wounded in the hospitals at night. In 1943 Patchaim Tajibayeva graduated from the University with honours. She was thinking... [читать подробенее]


  • - VII. Speak on the Soviet Union's achievements in different spheres of life. Make use of the text and the additional passages given in Exercises V, VI. 1 страница

    UNIT FIFTEEN THE SOVIET UNION TODAY Topics and Texts for Discussion* V. I. Lenin, the founder of the first socialist state. The Great October Socialist Revolution, a turning point in the history of mankind. The USSR, a voluntary union of free nations. The new Constitution of the USSR. Fundamental human rights guaranteed to Soviet citizens. The Soviet socialist way of life. Large-scale construction in the USSR. Contribution of Komsomol members to the economic development of the country. The... [читать подробенее]


  • - Read the text with a dictionary and do the exercises that follow it.

    Text 1. From the history of Belarus Additional texts for reading Exercises 1. Replace the following definitions by one word from text 3: – land along each side of a river or canal; – things, circumstances, surroundings, that make life easy or pleasant; – a part of a town or a country marked out for a special purpose; – to be shut in on all sides; – buildings and equipment of an institution, factory; – buildings where goods are made (esp. by... [читать подробенее]


  • - Read the text with a dictionary and do the exercises that follow it.

    Text 1. From the history of Britain Additional texts for reading Speak about London. Use the information from text 2 as a help to your topic. Exercises 1. Answer the questions on the text: 1. Where is London situated? 2. What parts does London consist of? What are they? 3. What is the City? What buildings is it famous for? 4. What is Westminster? What places of interest does it include? 5. What is Westminster Abbey famous for? 6. What is the richest... [читать подробенее]