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Biomolecules 

Living bodies are made up of biomolecules like carbohydrates, lipids, hormones, enzymes, proteins and vitamins. They are very essential for the growth, reproduction and maintaining health. The relation of biomolecules in living organisms is:
Biomolecules    Organelles    Cells    Tissues   Organs    Living organism 
* Cells need energy for various activities. Reactions involving ΔG > 0 are called endergonic and ΔG < 0 are called exergonic reactions.
* Living organism needs food. Food consists carbohydrates like starch, glucose; cotton, silk, rayon and wooden furniture consists cellulose. Previously carbohydrates were considered as 'hydrates of carbon' i.e., Cx (H2O)y. Carbohydrates such as deoxy ribose (C5H10O4), rhamnose (C6H12O5) cannot be represented as hydrates of carbon. Compounds like acetic acid (CH3COOH), methanal (HCHO) can be represented by Cx (H2O)but do not behave like carbohydrates. So previous definition is changed as "optically active polyhydroxy aldehydes or polyhydroxy ketones or the compounds which give these Aldehydes or ketones on hydrolysis are called carbohydrates". As they give sweet taste, they are called Saccharides (in Latin Saccharum = sugar).
Based on their behaviour towards hydrolysis they are classified into mono saccharides (compounds which do not hydrolyse into simpler carbohydrates eg: glucose, fructose), Oligo Saccharides (compounds on hydrolysis give 2-10 molecules of mono saccharides) like di saccharides (compounds on hydrolysis give 2 molecules of mono saccharides. eg: sucrose, maltose, lactose) and poly saccharides (compounds on hydrolysis give 100 to 3000 molecules of mono saccharides eg: starch, cellulose).
              The carbohydrates which contain Aldehyde or ketone group in hemiacetal or hemiketal form are capable of reducing Fehling's solution or Tollen's reagent are called reducing sugars (eg: all mono saccharides, maltose, lactose). On the otherhand sugars which do not reduce Fehling's solution and Tollen's reagent are called non reducing sugars (eg: sucrose, all poly saccharides).

 

Mono Saccharides:
Glucose: Glucose occurs in free state in ripen grapes, honey, mangoes, apples, peaches, pears. It occurs in combined state in glycosides, disaccharides and polysaccharides. It is also called as 'grape sugar' or 'dextrose'. It can be obtained either by boiling sucrose with dil. HCl in alcoholic solution or by hydrolysis of starch by boiling it with dil. H2SO4 at 393 K. Its molecular formula is C6H12O6.
Structure of glucose was proposed by Baeyer.

 

STRUCTURE OF GLUCOSE

¤ The molecular formula of glucose is C6H12O6.

¤  The formation of n - Hexane with HI & Red P indicates straight chain for glucose.

¤  The formation of oxime with NH2OH & the formation of cyanohydrin with HCN indicates presence of  group.

¤  The formation of gluconic acid with Br2 water indicates presence of -CHO group.

¤  The formation of saccharic acid with HNO3 indicates presence of one primary - OH group.

¤  The formation of pentaacetate with acetic anhydride indicates presence of five - OH groups.

¤ From these facts, open chain structure of glucose is
 
As open chain structure of glucose could not explain the non formation of addition compounds with NaHSO3, NH3, 2, 4 - DNP and muta rotation (The Spontaneous change in specific rotation of an optically active compound), Haworth Cyclic pyranose structure is suggested to explain all the properties of glucose.

α - D - (+) Gluco pyranose

Fructose: Fructose occurs in free state in honey and sweet fruits. It is also called as Laevulose or fruit sugar. Its molecular formula is C6H12O6


 

Disaccharides:
Sucrose (C12H22O11): It is also called as cane sugar or table sugar. It is manufactured either from sugar cane or beet root. Sucrose is a disaccharide.
              
                     C12H22O11  +  H2 C6H12O6  +   C6H12O6
                       Sucrose                                               Glucose           Fructose

             Which on hydrolysis gives α -D glucose and β -D fructose. Sucrose is dextro rotatory but after hydrolysis it gives dextrorotatory glucose and laevorotatory fructose. As Sucrose on hydrolysis gives equimolar mixture of glucose and fructose, it is called "Invert Sugar". The change in the sign of rotation from + (dextro) to - (laevo) is called inversion. The glycosidic linkage (ethereal linkage between 2 mono saccharides) is present between C1 - α of glucose and C2 - β of fructose. Sucrose is a non-reducible sugar, as hemiacetal -OH groups of both glucose and fructose are involved in the formation of glucosidic linkage.

Maltose (C12H22O11): Maltose is present in sprouted barley seeds. It can be prepared by the hydrolysis of starch using diastage. Its molecular formula is C12H22O11

 (C6H12O5)n   +   H2O     C12H22O11  +   H2O     2C6H12O6
          Starch                                                  Maltose                                             Glucose
he glycosidic linkage is formed between C1 - α of first glucose unit and C4 - α of second glucose unit . It is a reducible sugar, as each glucose unit has one hemiacetal hydroxyl group.


Lactose: As it occurs in cow's milk (4 -5)% and human milk (6 - 8)% it is also called as 'milk sugar'. It is a disaccharide of β - D - glucose and β - D - galactose. Lactose on hydrolysis gives glucose and galactose.

 C12H22O11   +   H2O          C6H12O6     +      C6H12O6
                 Lactose                                                  β-D glucose         β - D galactose

The glycosidic linkage is formed between C1 - β of galactose unit and C4 - β of glucose unit. It is a reducible sugar as it has hemi acetal hydroxyl group in each glucose and galactose units.


                     Structure of Lactose

 

Polysaccharides:
The carbohydrates which gives 10 or more mono saccharides on hydrolysis are called polysaccharides.
eg: Starch, cellulose, dextrin, glycogen.


Amylopectia

 

Starch: It is a polysaccharide of α - D - glucose. It is present in wheat, rice, maize, potato and corn. Molecular formula is (C6H10O5)n. It has 10 - 20% water soluble 'amylose'. Amylose gives blue colour with iodine solution. It has 200 -1000 α - D - glucose units (in long unbranched chain) are joined by α - glycosidic linkage between C1 of first glucose unit and C4 of second glucose unit. Its molecular mass may be between 10,000 to 50,000U. Starch also contains 80 - 90% water insoluble 'amylopectin'. It does not give blue colour with Iodine solution. It has 25 - 30 D - glucose units. α - glycosidic linkage is present between C1 of  1st glucose unit and C4 of 2nd glucose unit. It is a branched chain, which is formed due to α - glycosic linkage present between C1 of glucose unit of 1st chain and C6 glucose unit of adjacent chain.
 

Cellulose:
            It is a polysaccharide of β - D  glucose. 90% cellulose is present in cotton, 40 - 50% cellulose is present in wood. Molecular formula of starch and cellulose is (C6H10O5)n β - D glucose units are joined by C1 of first β - D glucose unit and C4 of second β - D  glucose unit. Cellulose molecule has 300 to 2500 β - D  glucose units. Its molecular mass is between 50,000 and 5,00,000 U. Due to hydrogen bonds, it has rigid linear structure. It is non reducible sugar. Only animals can digest cellulose as they have cellulose enzymes in the intestines.

Glycogen: It is called animal starch as its structure is similar to amylopection. This carbohydrate is stored in liver, muscler brain of animal body. It is also found in yeast and fungi

Uses of Carbohydrates:
¤ Vitamin C is prepared from glucose.
¤ Streptomycin, Kenamycin, Neomycin, Gentamycin are Carbohydrate antibiotics used to kill bacteria (which are resistant to penicillin).
¤ Cellulose acetate is used to manufacture rayon and plastics.
¤ They are sources of energy.
¤ Calcium glucosate is used to treat calcium deficiency.

Protein

Proteins are polypeptides formed by condensation polymerization of α - amino acids with molecular mass higher than 10,000 U. They are present in skin, muscles, nails, hair, tendons, arteries, connective tissues, enzymes, hormones. A peptide bond is formed when - NH2 of one amino acid reacts with - COOH of another amino acid
                             
             On the basis of molecular structure they can be classified as (a) fibrous proteins (keratin in nails, skin, hair, wool, myosin in muscles, collagen in tendons, fibroin in silk) (b) globular proteins (enzymes, insulin antibodies, albumin, haemoglobin). On the basis of nature of products of hydrolysis can be classified as (a) simple proteins (albumin of egg white, glutemin of wheat, keratin of hair, nails). (b) conjugate proteins (contains non - protein prosthetic group in addition to α - amino acids). (c) derived proteins (proteose, peptone, polypeptide).


Structures and shapes of proteins are studied at 4 different levels as
Primary structure: It explains the sequence of amino acids.
Secondary structure: It explains the shape of polypeptide chain.
Tertiary structure: It explains 3 dimensional arrangement of all the atoms in the protein.
Quaternary structure: It explains the way of special arrangement of sub units (individual chains).
             The lose of biological activity of a native protein due to physical or chemical change or change in pH or temperature is called "denaturation of protein". Denaturation of protein is due to disturbed hydrogen bonds and destroyed 2° & 3° structures of proteins.
e.g.: Coagulation of egg white on boiling.


Amino Acids

             Bifunctional organic molecules containing - NH2 & - COOH group are called amino acids. Out of 700 naturally occurring amino acids, 20 are important as they occur in almost all proteins. The amino acids which are not prepared by body must be supplied through food are called "essential amino acids" (Valine, Leucine, Isoleucine, Arginine, Lysine, Threonine, Histidine, Methionine, Phenylalamine, Tryptophan). The remaining 10 amino acids are prepared by body are called "non - essential amino acids".
                


 All amino acids have primary amino group. Where as proline
                   


             Except glycine (H2NCH2COOH) all other natural α - amino acids are optically active. They are colourless, crystalline solids. They are highly polar in water and forms zwitter ion.


At particular pH, zwitter ion acts as neutral and does not migrate to either anode or cathode. This pH is "isoelectric point". Iso electric point of neutral amino acids is slightly less than 7 (eg: glycine = 6.1) for acidic amino acids pH is 3.0 - 5.4 (eg: aspartic acid = 3.0), for basic amino acids pH is 7.6 - 10.8 (eg: Lysine = 9.7)


Nucleic Acids

   Nucleic acids are long chain bio polymers of nucleotides having polyphosphate ester chain. 2 main types of nucleic acids are RNA and DNA. Nucleic acids contain sugar with bases (either pyrimidine bases i.e. uracil, cytosine, thymine (or) purine bases i.e. Adenine and Guanine).
                          
                          Base + Sugar    Nucleoside
                          Base + Sugar + Phosphate    Nucleotide


DNA:
              Deoxy Ribonucleic acid (DNA) contain 2 - deoxy D - ribose sugar. It has bases Cytosine, Guanine, Adenine and Thymine. It has double stranded α - helix structure. It is present in nucleus of cell. It controls the transmission of hereditary effects. In
DNA, A = C & C = G but A + G = C + T. For human beings   ratio is 1.52 (for E.Coli = 0.93)

Double helix
             DNA double helical structure is given by F.H.C. Crick & J.D. Watson. Two strands are anti parallel. The diameter of double helix is 2 nm, the length of one turn is 3.4 nm. When DNA is heated, 2 strands separate out on cooling, they come closer (annealing). 


RNA:
  Ribonucleic acid contain D - ribose sugar. It has bases Cytosine, Guanine, Adenine and Uracil. It has single stranded α - helix structure. It is present in cytoplasm of the cell. It controls the synthesis of proteins.
Heredity - The Genetic Code:
            Nucleic acids control heredity at molecular level. Heredity information of an organism is stored in the double helix of DNA in the coded form (sequence of bases A, C, G, T). CUU is code for leucine. Specification of amino acid by 3 base sequence is known as 'genetic code'. It is universal, commaless, degenerate and 3rd base in codon is less specific.
             
            The synthesis of new identical copy of DNA from a DNA is called "replication". The synthesis of mRNA from DNA in the nucleus of the cell where genetic information passed from DNA to mRNA is called 'transcription". The process of decoding genetic message present in mRNA to form a proteinis called "translation". The genetic information of a cell is contained in 46 chromosomes.

 

Enzymes

            Biochemical reactions like digestion of food takes place slowly but occur fast in presence of enzymes (biocatalysts). The name of the enzyme ends with -ase. Enzymes are globular proteins and boilogical catalysts. Enzymes are specific for a particular reaction & for a particular reactant. Non protein part of enzyme is called "prosthetic group". When prosthetic group is bonded with enzyme, it is called "cofactor".
                         

 

Vitamins
            Naturally occurring organic compounds, which are required in small quantities for the maintenance of normal health of organism. Vitamins are classified into water soluble vitamins (B & C) and fat soluble (A, D, E, K) Vitamins. Biotin is neither soluble in water nor in fat.

        Vitamin

               Sources

       Deficiency Diseases

               A

        (Retinol)

Carrot, Mango, Butter
Papaya, Fish Oils

Night blindness,
Xerophthalmia (Redness of eyes)

              D
      (Calciferol)

Sun light, Butter, Milk,
Fish liver oil

Rickets (in children)
Osteomalacia (in adults)

              E

Wheat germ oil, Soyabeen

oil, Sunflower oil, Eggs

Sterility, weakness of
heart muscles

              K

Green leafy vegetables,

Cabbage, Carrot tops

Haemorrhage, delay of blood clotting

C

    (Ascorbic acid)

Orange, Lemon, Amla,

Scurvy, Pyorrhea

B1 (Thiamin)

Rice, Wheat, Milk, Fruits

Beriberi & loss of appetite

B2 (Riboflavin)

 Yeast, Milk,

Cheilosis, Glossitis, Dermatitis

B3 (Protothemic acid)

 All the foods

Burning of feet

 

B5 (Nicotinic acid)

Yeast, Milk, Meat

Pallegra, Dermatitis

B6 (pyridoxine)

Yeast, Meat, Eggs

Convulsions, Dermatitis

H or B7 (Biotin)

Yeast, Milk, Liver

Paralysis, Loss of hair

B9 (Folic acid)

Spinach

Anaemia, Inflamation of tongue

          B12

(Cynocobalamine)

Ox liver, Fish, Milk

Pernicious anaemia,
Hyperglycemia

B1, B2, B6, B12 Vitamins together called B - complex. It is found in milk, liver, cereals, used to prevent beriberi and pernicious anaemia.

* As vitamin C is water soluble and readily excreted in urea and cannot be stored in our body. So it must be supplied regulary in diet.
 

HORMONES
Hormones are biomolecules that transfers biological information from one group of cells to distanct organs in human body. Hormones have many functions in our body. They help in maintaining the balance of biological activities in the body. Enzymes insulin and glucagon together regulate the glucose level in the blood. Low level of thyroid gland "Thyroxine" leads to hypothyroidism (causes obesity, lethargyness). Low level of iodine in the diet may also lead to hypothyroidism. So iodised salt is advised in food.

           Hormones released by adrenal cortex, like glucocorticoids control the carbohydrate metabolism, in the reactions of stress. Mineralocorticoids control the water and salt by the kidney. Stress, weakness, Addison's disease are due to malfunctioning of adrenal cortex. It can be rectified by treating with glucocorticoids and mineralocorticoids.
           Hormones released by testes in males and ovaries in females are responsible for secondary sex characters. Male sex hormone testosterone is responsible for deep voice, facial hair, general physical constitution. Female sex hormone 'Estradiol' is responsible for shrill voice, long hair, breast development and control of menstrual cycle. Another female sex hormone is useful for preparing the uterus for implantation of fertilised egg.

Posted Date : 06-08-2021

గమనిక : ప్రతిభ.ఈనాడు.నెట్‌లో కనిపించే వ్యాపార ప్రకటనలు వివిధ దేశాల్లోని వ్యాపారులు, సంస్థల నుంచి వస్తాయి. మరి కొన్ని ప్రకటనలు పాఠకుల అభిరుచి మేరకు కృత్రిమ మేధస్సు సాంకేతికత సాయంతో ప్రదర్శితమవుతుంటాయి. ఆ ప్రకటనల్లోని ఉత్పత్తులను లేదా సేవలను పాఠకులు స్వయంగా విచారించుకొని, జాగ్రత్తగా పరిశీలించి కొనుక్కోవాలి లేదా వినియోగించుకోవాలి. వాటి నాణ్యత లేదా లోపాలతో ఈనాడు యాజమాన్యానికి ఎలాంటి సంబంధం లేదు. ఈ విషయంలో ఉత్తర ప్రత్యుత్తరాలకు, ఈ-మెయిల్స్ కి, ఇంకా ఇతర రూపాల్లో సమాచార మార్పిడికి తావు లేదు. ఫిర్యాదులు స్వీకరించడం కుదరదు. పాఠకులు గమనించి, సహకరించాలని మనవి.

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