2. Кратко расскажите по-английски:

а) какие функции выполняют жиры;

б) о способности животного организма производить жиры.

Работа над текстом № 4 «proteins»

Active Vocabulary:

protein (complete, partially complete, incomplete); to vary variation; to link, to maintain, maintenance, to value, value, valuable; to support; to classify; to result in; to base upon; adequate; to be able, ability

Proteins differ from carbohydrates in that, besides the elements present in sugar and starches, they also contain nitrogen and in most cases sulphur. Phosphorus and iron are also found in some proteins. The importance of nitrogen content commonly varies from 10 to 18 per cent. Proteins are found in foods of both animal and plant origin. Meat, eggs, milk, nuts and certain of cereal foods are high in protein. All those foods contain more than one protein. Milk, for example, contains the proteins, lactalbumin and casein, as well as others of lesser importance.

Proteins are complex in nature, they are composed of a number of amino acids or “building blocks”, linked together, and also of amino acids linked with other substances. Proteins vary in the kind and number of amino acids present. Certain amino acids the body is unable to build. These are known as essential amino acids and must be supplied by the foods eaten.

Variation in the quality of proteins has resulted in their classification as complete, partially complete, and incomplete, based upon their ability to support normal growth and to maintain life even if it is the only protein in the diet. A partially complete protein is one that maintain life but does not support normal growth. An incomplete protein, although valuable in the diet, will by itself neither support normal growth nor maintain life. Most animal proteins are complete. Plant proteins are more or less incomplete, although the soya bean and the wheat grain contain proteins that are complete. Valuable sources of protein are: cereals and cereal products, cheese, eggs, fish, meat, milk, nuts.

Задания

1. Ответьте на вопросы:

1. What is the composition of proteins? 2. What foods are valuable sources of proteins? 3. What is the basis of protein classification?

2. Кратко расскажите по-английски:

а) о составе белков;

б) о принципе классификации белков и их характеристике.

Работа над текстом № 5 «vitamins»

Active Vocabulary:

vitamin; health; well-being; to expose, exposure; to aid, aid; to constitute, constituent; to destroy, destruction, destructive; available; extent; to exceed; to remain, to recognize, to convert (to transform, to change into, to turn into), to affect (to influence, to act upon, to have effect), to prevent; to occur (to happen, to take place); stable; readily

The food constituents known as vitamins are exceedingly important in nutrition even though they are required only in small amounts. Vitamins are essential for good nutrition and health and for normal growth and development. Those vitamins that are generally recognized as essential, and some of those that may be essential, are considered here. Though many vitamins are available in the form of concentrated or in pure synthetic preparations, or both, foods still remain the best source of these important substances.

Vitamin A was first discovered in butter, egg yolk, fish liver oil, and green vegetables. It stimulates growth and aids in general well-being. Vitamin A occurs as such in animal foods. It occurs in certain vegetables as carotene or provitamin A, a bright yellow pigment which the body changes to vitamin A. This vitamin is stable to heat and, since it is a fat-soluble substance, does not dissolve to any appreciable extent in water. But it is not stable to light, especially ultra-violet light. Foods which are rich in vitamin A are butter, cheese, cream, eggs, fish oil, fruits, liver, milk.

Vitamin D. The antirachitic or “sunshine” vitamin, is really “stored sunshine” in food. This storage is due to the presence of ergosterol, a fat-like substance in food, which is called a provitamin D, and under direct exposure to the sun or to ultraviolet light for short daily periods, this substance is converted into vitamin D within the body. Unlike most of the other vitamins, this one is not easily destroyed and is stable to heat, alkalis¹, acids, and oxidation. Vitamin D is essential for the development and maintenance of bones and teeth. Yeast contains ergosterol which can be irradiated by ultraviolet light and thus transformed into vitamin D. Sources of vitamin D are: butter and egg yolk, fish liver oil, oily fish.

Vitamin E affects reproduction and fertility growth, muscle tone and the condition of the nervous system. It has also a function in preventing the destruction of other foods through oxidation. Heat does not dissolve it, but it is easily oxidized. The best sources of vitamin E are the vegetable oils, butter, eggs, green leaves and liver.

Vitamin K is necessary for normal clotting² of the blood. Heat has little effect upon vitamin K and, like the ether fat-soluble vitamins, it is not soluble in water. Alkalis¹, strong acids and sunlight destroy this vitamin. Foods rich in vitamin K are cabbage, cauliflower, fish liver.

Ascorbic acid, known as vitamin C is the least stable of all the vitamins. It oxidizes readily, and in the presence of heat, alkali¹, and oxygen, oxidation goes on rapidly. Ascorbic acid is water-soluble. The best sources of this vitamin include: citrus fruits, peppers, strawberries, vegetables, tomatoes.

1 –alkali – щелочь мн.ч. – s/-es

2 - свертывание