Lesson 10

A. Vitamin В

Vitamin В is known to prevent polyneuritis (nervous symptoms). Scientists also proved the lack of this vitamin to cause loss of appetite, emaciation and general weakness. Vitamin В appears to be widely distributed in natural human foods and stock feeds. The unmilled cereal grains, fresh green forage and hay contain it. One may find vitamin В in milk and whey. Yeast is especially rich in vitamin B. Though vitamin В can be destroyed by prolonged heating at temperature above the boiling-point, it is stable in ordinary feeds.

For example, it has been found that whole rice stored in an arid climate for 100 years was still rich in it. Also the vitamin В complex can be synthesized in the paunch, of ruminants through the action of bacteria.

Vocabulary List

polyneuritis (n) - полиневрит forage (n) - корм

emaciation (n) - истощение hay (n) - сено

distribute(v) - распространятьcontain(v) - содержать в себе

food (n), feed(n) - пища, корм rich (a) - богатый

whey(n) – сыворотка (молочная)

human(a) - человеческийrice(n) - рис

stock(n) - скот, поголовьеyeast(n) - дрожжи

destroy(v) - разрушать, уничтожать

mill(v) - молоть (зерно)store(v) - запасать, хранить

cereal grains - злаковые зерна prolonged (a) - длительный

fresh (a) - свежий heating (n) - нагревание

paunch– рубецarid(a) - сухой (о климате)

Exercise 1. Translate text 10 A. into Russian.

Exercise 2. Answer the following questions to text A.:

1. What are the peculiarities of vitamin B?

1. What do you know about vitamin В?

Exercise 3. Answer the following questions to text in Russian and then in English:

1. What disease is vitamin В known to prevent?

2. What symptoms does the lack of vitamin В cause?

2. Where is vitamin В found?

3. What is especially rich in vitamin B?

4. What destroys vitamin B?

5. In what feeds is vitamin В stable?

6. What action is there in the paunch of ruminants?

B. Thiamine (Vitamin B₁) and Riboflavin (Vitamin B₂)

In 1890 studies were begun in order to isolate and characterize thiamine as a vitamin. Beriberi is known to be caused by lack of thiamine. Characteristic signs of thiamine deficiency are supposed to be loss of appetite and weight. In advanced stages polyneuritis may occur, involving degeneration of peripheral nerves. We know thiamine to occur in natural foods and other biological materials, either in the free or in a combined form. Yeast, cereal grain, pork, nuts are especially rich in thiamine.

Characterizing thiamine we may say that in its pure form thiamine is a white crystalline powder with yeasty odor and a salty, nut-like taste.

Riboflavin, known also as vitamin B₂, consists of ribose sugar combined with flavin. The compound is known to have been prepared synthetically. One may find riboflavin in milk, egg white, liver, and green leaves. Heart, pancreas, muscles, kidneys, brain, and other organs contain it. It is present in grains and legumes. It was found to be destroyed by oxidation and light.

Riboflavin is required in the metabolic processes of animals. It is not, however, dietary requirement in ruminants, for in these animals the vitamin is synthesized by bacterial action in the rumen.

Experiments indicate that intestinal synthesis is not adequate to meet horse's requirements for this vitamin and that a dietary source is necessary. A lack in riboflavin in chicks results in failure to grow, paralysis and death. Poor hatchability and high mortality of the embryo may be seen in mature chickens.

Exercise 4. Read, translate the text "Riboflavin" using a dictionary and answer the following questions:

1. Когда начались исследования по выделению тиамина в качестве витамина?

1. Чем вызывается бери-бери?

2. Каковы последствия дефицита этого витамина?

4. Где встречается тиамин?

5. Что представляет собой тиамин?

6. Что представляет собой рибофлавин

7. Какова роль рибофлавина в организме?

8. Где встречается рибофлавин?

9. К чему приводит недостаток рибофлавина у цыплят?