III. Independent Work: Chemical Elements of Living Matter

Exercise 1. Read the text and answer the question: What substances are spoken about in this text?

Chemical Elements of Living Matter

Living matter contains about one third of the elements of Mendeleev's Periodic Table. Only hydrogen, carbon, nitrogen and iodine are found in higher concentration in the human body than in the Earth. Six other elements are found in roughly the same proportions: oxygen, phosphorus, sulphur, chlorine, potassium and calcium.

Certain organisms may accumulate considerable amounts of elements that do not normally occur in the human body.

Besides hydrogen, oxygen is the element present in the human body in the greatest amount constituting about 65 % of the total (by weight) amount.

The most amount of oxygen is combined with hydrogen as water. It is generally recognized that the primeval life forms' developed in the waters of the Earth and the evolution of animals progressed much in the sea.

The heritage of our remote origins is still contained within us - the most abundant compound constituting the human body is water which constitutes 45 % to 75 % by weight. The exact amount depends principally on age, sex and build; relatively, infants have more than adults, men more than women. There may also be considerable differences between healthy and ill people and the water content of the body may be affected by drugs.

The next most common element is carbon to which about one half of the body weight of tissues is due. The unique nature of living matter is due to its organic constituents, that is, compounds, based on a carbon chain.

There are important inorganic constituents of the body, in addition to water. Sodium, potassium, chlorine are present as the ions, and so are part of calcium, magnesium, iodine and bromine. The total body sodium in a young adult is about 58 mmol/kg² (1.3 g/k). The normal recommended intake of NaCl is 1 g per kg of water. Most western European and American diets contain 6-8 g of NaCl per day which, in a temporate climate, is much greater than required. The total body potassium in a young adult man is about 50 mmol/kg (1.9 g/k). It is somewhat less in women and decreases slightly with advanced age. An adult man was about 16.7 mmol/kg (400 mg/kg) of magnesium in his body, about half of which is present in bones. The concentration of magnesium in cells is about 7.5 mmol/1, about 1/3 of this is protein-bound³.

Other important ions occurring in living matter, besides those formed from organic acids and bases, are bicarbonate, ammonium, phosphate and sulphate. The bony skeleton and the teeth contain lithium fluoride⁴ as well. Additional important inorganic compounds include carbon dioxide and oxygen. Most of nitrogen, sulphur and iodine and the heavy metals are present in organic molecules. About one tenth of phosphorus is combined with organic compounds.

Notes:

'primeval life forms - початкові форми життя

²mmol/'kg - концентрація речовин у розчині, що відповідає одній тисячній грам-молекули в 1 л розчину чи 1 кг маси

³protein-bound - зв'язаний з білком

⁴lithium fluoride - фтористий літій, фторид літію

Exercise 2. Read the sentences and name the tense and voice of the verbs; translate the sentences into Ukrainian.

1. The primeval life forms developed in the waters of the Earth. 2. The evolution of animals progressed greatly in the sea. 3. The exact amount of water in the human body depends on a person's age, sex and build. 4. Carbon constitutes about one half of the body weight. 5. The amount of potassium decreases slightly with advanced age. 6. The water content of the body is affected by drugs. 7. Heavy metals are present in organic molecules.

Exercise 3. Read the sentences. Put the verbs in brackets in the correct form.

1. Hydrogen, carbon, nitrogen and iodine (to find) in higher concentrations in the human body than in the Earth. 2. Oxygen in the living matter (to constitute) 65 % of the total amount 3. Primeval life forms (to develop) in the waters of the Earth. 4. The most amount of oxygen (to combine) with hydrogen as water. 5. The total body potassium (to decrease) slightly with advanced age. 7. The bony skeleton and the teeth (to contain) lithium fluoride as well.

Exercise 4. Answer the following questions using the text.

1. What amount of chemical elements does living matter contain? 2. What elements are recognized as the most abundant in nature and human body? 3. What elements are found in the human body in higher concentrations than in the Earth's crust? 4. Is it right to say that primeval life forms developed in water? 5. Why does water constitute most part of the human body? 6. What does the exact amount of water in an adult and an infant depend on? 7. Is there any difference in water content in healthy and ill people? 8. What is the unique nature of living matter due to? 9. When does the total body potassium decrease? 10. What is the recommended dose of sodium chloride intake daily? 11. What chemical elements do bones and teeth contain? 12. What amount of phosphorus is combined with organic compounds? 13. What parts of the human body contain nitrogen, sulphur, iodine?

LESSON THIRTY-FIVE

I	Speaking	At the Chemist's
II	Grammar	1. Дієслово у Future Perfect та Future Perfect Continuous(§92). 2. Скорочені стверджувальні і заперечні речення типу Soshall I, Neither (nor) did he (§93)
III	Independent Work	Aspirin