Unit 2. Molecular organization

Essential vocabulary

aldehyde to accelerate aqueous

arrangement to alter amphoteric

balance to assist essential

bonding to constitute exact

branch to contract favourable

breakdown to dissolve fatty (acid)

carbohydrate to resist gastric (juice)

carbon dioxide to require inner

carrier to reduce liquid

chain to solve osmotic

chlorophyll to yield outer

deficiency ribonucleic (acid)

deoxyribose saturated

enzyme soluble

environment toxic

gravity vital

haemoglobin variable

hormone

intake

kidney

leakage

malformation

membrane

metabolism

nitrate

nucleotide

quantity

source

urine

vitamin

Назовите прилагательные, соответствующие существительным:

Deficiency, enzyme, environment, hormone, kidney, membrane, metabolism.

Аналитическое чтение.

Now we know that the electron shells around an atom may each contain a maximum number of electrons. The shell nearest to the nucleus may possess a maximum of two electrons and the next shell a maximum of eight. An atom is most stable, i.e. least reactive, when its outer electron shell contains the maximum possible number of electrons. For example, helium, with a full complement of two electrons in its outer shell, is inert. In a hydrogen atom, the electron shell has a single electron and so the atom is unstable. If two hydrogen atoms share their electrons, they form a hydrogen molecule, which is more stable. The two atoms are effectively combined and the molecule is written as H₂. The sharing of electrons in order to produce stable molecules is called covalent bonding.

2.1 Inorganic ions

Water is the most important inorganic molecule in biology. Dissolved in the water within living organisms are a large number of inorganic ions. Typically they constitute about 1% of an organism by weight, but they are nonetheless essential. They are divided into two groups: the macronutrients or major elements which are needed in very small quantities, and the micronutrients or trace elements which are needed in minute amounts (a few parts per million). Although the elements mostly fall into the same category for plants and animals, there are a few exceptions. Chlorine, for example, is a major element in animals but a trace element in plants. In addition to the essential elements listed in Table 2.1, some organisms also have specific requirements such as vanadium, chromium and silicon.

Table 2.1.

Macronutrients/ Major elements	Functions	Notes
Nitrate No3^- Ammonium NH4^+	Nitrogen is a component of amino acids, proteins, vitamins, coenzymes, nucleotides and chlorophyll. Some hormones contain nitrogen, e.g. auxins in plants and insulin in animals.	Deficiency in animals and humans is not vital.
Phosphate PO4^3- Orthophosphate H2PO4^-	A component of nucleotides and some proteins. Used in the phosphorylation of sugars in respiration. A major constituent of bone and teeth. A component of cell membranes in the form of phospholipids.	In animals and humans, deficiency can result in a form of bone malformation called rickets.
Sulphate SO4^2-	Sulphur is a component of some proteins and certain coenzymes, e.g. acetyl coenzyme A.	Deficiency in animals and humans is not vital.
Potassium K^+	Helps to maintain the electrical, osmotic and anion/ cation balance across cell membranes. Assists active transport of certain materials across cell membrane. Necessary for protein synthesis and is a co-factor in photosynthesis and respiration.	Potassium plays an important role in the transmission of nerve impulses. Deficiency in animals and humans is not vital.
Calcium Ca^2+	It aids the translocation of carbohydrates and amino acids. It is the main constituent of bones, teeth and shells in animals. Needed for the clotting of blood and the contraction of muscle.	In animals and humans, deficiency leads to rickets and delay in the clotting of blood.
Sodium Na^+	Helps to maintain the electrical, osmotic and anion/ cation balance across cell membranes. Assists active transport of certain materials across the cell membrane.	In animals and humans, it is necessary for the functioning of the kidney, nerves and muscles; deficiency may cause muscular cramps.
Chlorine Cl^-	Helps to maintain the electrical, osmotic and anion /cation balance across cell membranes. Needed for the formation of hydrochloric acid in gastric juice. Assists in the transport of carbon dioxide by blood.	In animals, deficiency may cause muscular cramps. Deficiency in humans is not vital.
Magnesium Mg^2+	A constituent of chlorophyll. An activator for some enzymes, e.g. ATPase. A component of bone and teeth.	Deficiency in animals and humans is not vital.
Iron Fe^2+ or Fe^3+	A constituent of electron carriers, e.g. cytochromes, needed in respiration and photosynthesis. A constituent of certain enzymes. Required in the synthesis of chlorophyll. Forms part of the haem group in respiratory pigments such as haemoglobin, haemoerythrin, myoglobin.	Deficiency in animals and humans leads to anaemia.
Micronutrients/ Trace elements	Functions	Notes
Manganese Mn^2+	An activator of certain enzymes, e.g. phosphatases. A growth factor in bone development.	Deficiency in animals produces bone deformations.
Copper Cu^2+	A constituent of some enzymes. A component of the respiratory pigment haemocyanin.	Deficiency in animals and humans is not vital.
Iodine I^-	A constituent of the hormone thyroxin, which controls metabolism.	Deficiency in humans causes cretinism in children and goitre in adults; in some other vertebrates it is essential for metamorphic changes.
Cobalt Co^2+	Constituent of vitamin B12, which is important in the synthesis of RNA, nucleoprotein and red blood cells.	Deficiency in animals causes pernicious anaemia
Zinc Zn^2+	An activator of certain enzymes, e.g. carbonic anhydrase.	Carbonic anhydrase is important in the transport of carbon dioxide in vertebrate blood.
Fluorine F^-	A component of teeth and bones.	Associates with calcium to form calcium fluoride which strengthens teeth and helps prevent decay.

Grammar 1. Множественное число существительных.

2. Степени сравнения прилагательных и наречий.

3. Типы вопросительных предложений

1. Образуйте множественную форму существительных:

Electron, shell, nucleus, molecule, quantity, category, plant, bone, tooth, muscle, constituent.

2. Образуйте сравнительную и превосходную степени сравнения прилагательных:

Deep, essential, exact, favourable, fine, liquid, narrow, rich, toxic, vital.

3. Сформулируйте как можно больше вопросов к предложениям:

а) Water is the most important inorganic molecule in biology.

b) Inorganic ions constitute about 1% of an organism by weight.

Summary

Прочтите тексты, пользуясь словарем, найдите наиболее важные в смысловом отношении предложения (фрагменты). Изложите содержание текстов на английском языке.

2.2 Carbohydrates

Carbohydrates comprise a large group of organic compounds which contain carbon, hydrogen and oxygen and which are either aldehydes or ketones. The word carbohydrate suggests that these organic compounds are hydrates of carbon. Their general formula is C_x(H₂O)_y. The word carbohydrate is convenient rather than exact, because while most examples do conform to the formula, e.g. glucose (C₆H₁₂O₆) and sucrose (C₁₂H₂₂O₁₁), a few do not, e.g. deoxyribose (C₅H₁₀O₄).

Carbohydrates are divided into three groups: the monosaccharides ('single-sugars'), the disaccharides ('double-sugars') and the polysaccharides ('many-sugars'). The presence of the hydroxyl groups allows carbohydrates to interact with the aqueous environment and to participate in hydrogen bonding, both within and between chains. Derivatives of the carbohydrates can contain nitrogens, phosphates and sulphur compounds. Carbohydrates also can combine with lipid to form glycolipids or with protein to form glycoproteins. This arrangement is typical of many organic molecules where single units, called monomers, are combined to form larger units, called polymers.

The functions of carbohydrates, although variable, are in the main concerned with storage and liberation of energy. A few, such as cellulose, have structural roles.