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Molecules which have polar nature are capable to form hydrogen bond are generally soluble in water. In sucrose and glucose hydroxyl groups are present, which is polar in nature. Therefore, they are involved in intermolecular hydrogen bonding with water molecules, so these compounds are readily soluble in water. On other hand benzene and cyclohexane are hydrocarbons. They do not have any polar group so they cannot make hydrogen bonds with water.
What are the expected products of hydrolysed of lactose?
How do you explain the absence of aldehyde group in the penta acetate of D-glucose?
Glucose reacts with hydroxylamine to form an oxime. where as, the penta acetate of glucose does not react with hydroxyl amine indicating the absence of free CHO group.
The melting points and solubility of water of amino acids are generally higher than that of the corresponding halo acids. Explain.
Amino acids are dipolar in nature (+NH3-CHR-COO-) and have strong dipolar interaction. Amino acids have amino (basic) group and carboxylic (acidic) group. A proton which comes from carboxylic group is accepted by amino group. Thus amino acid exists in the form of Zwitter ion.
Due to this ionic form, amino acids become crystalline solids and due to this salt like structure, show higher melting point.
Where does the water present in the egg go after the boiling the egg?
Denaturation of proteins is a process in which physical and biological properties of protein without changing the chemical composition of protein. In an egg denaturation of protein is the coagulation of albumin present in the white of an egg. When egg is boiled in water, the globular proteins present in it changes to a rubber like insoluble mass which absorbs all water present in the egg.
Vitamin C is a water soluble vitamin also vitamin C is rapidly absorbed from intestine. Since it is water soluble, it is not stored in the body and excess amount of vitamin C removed through urine.
What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?
When a nucleotide from the DNA containing thymine is hydrolyzed, thymine β-D-2- deoxyribose and phosphoric acid are obtained as products.
When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?
Complete hydrolysis of RNA yields a pentose sugar(D-ribose), phosphoric acid and nitrogen containing heterocyclic compounds (called bases). Such as guanine (G), cytosine (C), Uracil (U), Adenine (A).
There is no relationship among the quantities of four bases obtained on complete hydrolysis of RNA. It is because base sequence in RNA is not fixed but depend on base sequence in DNA i.e., the base sequence in a specific RNA is controlled by that of DNA which is controlling RNA synthesis (i.e., transcription). The base sequence in DNA indirectly controls the sequence of amino acids in the protein.
Carbohydrates are primarily produced by plants and form a very large group of naturally occurring organic compounds. Some common examples are cane sugar, glucose, starch, etc. They have the general formula Cn(H2O)n.
Give one example each of (i) Reducing sugar and (ii) Non-reducing sugar.
State two characteristics of monosaccharides.
Name a carbohydrate containing five carbon atoms per molecule.
Name the polysaccharides that is stored in the liver of animals.
What do you understand by the term gycosidic linkage?
The two monosaccharides are joined together by an oxide linkage formed by the loss of a water molecule. Such a linkage between two monosaccharide units through oxygen atom is called glycosidic linkage.
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What are the hydrolytic products of lactose?
What is meant by inversion of sugar?
Why is cellulose not a food for human beings?
Name three useful products that can be obtained from cellulose.
What are monosaccharides?
A carbohydrate that cannot be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone is called a monosaccharide. Example: Glucose
What are reducing sugars?
A reducing sugar is any sugar that is capable of acting as a reducingagent because it has a free aldehyde group or a free ketone group. All monosaccharides are reducing sugars.
Write two main functions of carbohydrates in plants.
(i) They serve as structural materials for cell walls. For example, the polysaccharide cellulose is the chief constituent of the plant cell wall.
(ii) Carbohydrates act as biofuels and provide energy for different functioning.
Classify the following into monosaccharides and disaccharides: Ribose, 2-deoxy-ribose, maltose, galactose, fructose and lactose.
Mono-saccharides: Ribose, 2-deoxyribose, galactose, fructose.
Di-saccharides: maltose, lactose.
What happens when sucrose is boiled with dilute HCl?
Give one reaction to show the presence of five hydroxyl groups in glucose.
How will you prove that all the carbon atoms of a glucose are in a straight chain?
Name the linkage when two monosaccharides unit join to form a polysaccharide unit.
What happens when starch is boiled with dil. HCl?
What happens when cellulose is heated by dil. H2SO4?
Define mutarotation.
Mutarotation is the change in the optical rotation because of the change in the equilibrium between two anomers, when the corresponding stereocenters interconvert. Cyclic sugars show mutarotation as α and β anomeric forms interconvert.
Draw the structure of the α-glucose and β-glucose.
Structure of the α-glucose and β-glucose.
Which of the following disaccharides contains a glycosidic linkage between glucose and glucose.
i)Sucrose
ii)Maltose
iii)Lactose
Which of the following disaccharides contains a glycosidic linkage between glucose and glucose Sucrose, Maltose, Lactose?
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What are the hydrolysis products of
(i) sucrose and (ii) lactose?
Sucrose on hydrolysis gives glucose and fructose.
(i) 
Lactose on hydrolysis gives glucose and galactose.
(ii) 
Name the water insoluble fraction of starch. Name the monomer of this.
-D-glucose.
Amylose and cellulose are both straight chain polysaccharides containing only D-glucose units. What is the structural difference between the two?
Name any two products derived from cellulose.
(i) Rayon: used in textile industry.
(ii) Gun cotton: used as an explosive.
Give one test to distinguish glucose and fructose.
How many members (atoms) will constitute the pyranose ring of glucose?
What is the basic difference betweeen starch and cellulose?
Why is glucose given to the patient under exhausation?
What is the action of bromine water on:
(i) glucose, (ii) fructose?
What are the products obtained on the fermentation of glucose?
What is an amino acid? Give one example.
Amino acids contain amino (–NH2) and carboxyl (–COOH) functional groups. For example glycine.
How do amino acids form proteins?
What are the monomers constituting proteins?
In what respect would any two naturally occurring amino acids differ from one another?
-amino acids. They are only differ by in the alkyl group.
Describe the bonds responsible for the secondary structure of proteins.
The secondary structure of protein refers to the shape in which a long polypeptide chain exist. The structure arise due to the regular folding of the backbone of the polypeptide chain due to hydrogen bonding between -NH- and 
groups of the peptide bond.
What type of bonding helps in stabilising the α-helix structure of proteins?
What type of bonding occurs in β-pleated sheet?
Give one example of denatured protein.
The coagulation of egg white on boiling is a example of denaturation.
What are enzymes?
Enzymes are proteins that catalyze biological reaction. They are very specific in nature and catalyze only a particular reaction for a particular substrate. Enzymes are usually named after a particular. For example, the enzyme used to catalyses the hydrolysis of maltose in glucose is named as maltase. 
Name the disease caused due to the deficiency of phenyalanine hydroxylase.
Write the names of enzymes whose deficiency causes albinism and phenyl ketone urea.
Write the name and the structure of the simplest amino acid which can show optical activity.
What do you understand by Zwitter ion?
Write the structure of Zwitter ion formed from alanine.
Zwitter ion formed fromed by alanine.
In the dipeptide Glycylalanine( Gly-ala), which amino acid has a free amino group and which has a free carboxyl group?
Give an example of irreversible protein denaturation.
Curding of milk which is caused due to the formation of lactic acid. An example of irreversible protein denaturation.
What is the importance of amino acids to us?
Proteins are the most abundant biomolecules of the living system. They occur in every part of the body and form the fundamental basis of structure and fuctions of life. They are also required for growth and maintenance of body. Amino acid is monomer of protein, thus they are required for formation of proteins.
What do you mean by peptide bond?
Peptide linkage is an amide formed between -COOH group and -NH2 group. The reaction of between two molecules of similar or different amino acids, proceeds through the combination of the amino group of one molecule with the carboxyl group of the other. This results in the elimination of a water molecule and formation of a peptide bond -CO-NH-. 
What is renaturation of protein?
The original structure of a protein is a three dimensional structure. The process of returning a denatured protein structure to its original structure and normal level of biological activity is known as renaturation of protein.
Which enzyme regulates the blood sugar level in the body?
What are nucleic acids?
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What is meant by Nucleotide?
What do you mean by Nucleoside?
What is meant by RNA and DNA?
What is the difference between ribose and deoxyribose?
What are different types of RNA found in the cell?
There are three types of RNA found in cell.
i) messenger RNA (m-RNA)
ii) ribosomal RNA (r-RNA)
iii) transfer RNA (t-RNA).
What type of bonds hold a DNA double helix together?
Where in the higher cells in the DNA molecules mainly located?
Name two purines bases in the nucleic acid.
The two purines bases are:
(i) Adenine, (A), (ii) Guanine (G).
Name the pyrimidine bases present in ribonucleic acid.
How many hydrogen bond are present between:
(i) A and T
(ii) C and G in a double helix structure?
(i) Between A and T, there exist two hydrogen bonds.
(ii) Three hydrogen bonds are present between C and G.
What do you understand by DNA replication?
The process of a making an identical copy of a DNA by using existing DNA as template for the synthesis of new DNA strands.
What is codon?
What are vitamins?
Give one source and one use of vitamin B6.
Write the chemical names of vitamin E and C.
Vitamin E—Tocopherols
Vitamin C—Ascorbic acid.
Give the importance of vitamin C.
The deficiency of which vitamin causes the disease 'pernicious anaemia'.
Fresh tomatoes are a better source of vitamin C than those which have been stored for sometime. Explain.
Why is vitamin 'B' called vitamin B complex?
State the importance of vitamin D.
Why are carbohydrates generally optically active?
What is the difference between ribose and 2-deoxyribose sugars?
Name a polysaccharide which is stored in the liver of animals as food reserve.
Consider a double helix. Are the base pairs?
part of the backbone structure
inside the helix
outside the helix
B.
inside the helix
What is the basic structural difference between starch and cellulose?
In what ways does starch show similarity with cellulose?
Starch and cellulose both are polysaccharides. They show similarity in the following ways:
(i) Both starch and cellulose do not reduce Fehling’s solution or Tollen’s reagent.
(ii) They do not form osazone.
(iii) Both are amorphons solid.
(iv) Both are polymers of D-glucose.
What happens when D-glucose is treated with the following reagents?
Hi.
Glucose on prolonged heating with HI, it forms n-hexane.
What happens when D-glucose is treated with the following reagents?
Bromine water
Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with a mild oxidising agent like bromine water.
What happens when D-glucose is treated with the following reagents?
HNO3.
On being treated with HNO3, D-glucose is converted to saccharic acid.
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The following reactions cannot be explained by its open chain structure:
(i) Despite having an aldehydic group, glucose does not give Schiff’s test and it does not react with sodium bisulphite and ammonia.
(ii) The penta-acetate of glucose does not react with hydroxylamine indicating absence of —CHO group.
(iii) Mutarotation: When glucose is crystallized from a concentrated solution at 30°C, it gives a form of glucose m.p. 146°C, [α]D = (+) 111°, on the other hand the β-form (m.p. 15°C), [α]D = (+) 19.2° is obtained on crystallization of glucose from a hot saturated aqueous solution at a temperature above 98°C. This behaviour cannot be explained by its open chain structure.
What are essential and non-essential amino acid? Give two examples of each type.
Essential amino acids : Those amino acids which are not synthesised by our body are called essential amino acids. They must be part of our diet. Their deficiency leads to diseases such as Kwashiorkor (water balance in the body is disturbed). Valine, leucine, isoleucine, phenyl alanine, methionine, tryptophan, threonine, lyslne, arginine and histadine are ten essential amino acids.
Non-essential amino acids: The amino acids, which can be synthesised in the body, are known as non-essential amino acid. They are also called dispersable amino acids e.g., glycine, alanine, seriqe, cysteine, glutamine, tyrosine, proline, aspartic acid, asparagine, glutamic acid.
Define the following as related to proteins:
(i) Peptide linkage (ii) Primary structure (iii) Denaturation.
i) Peptide linkage: In peptide linkage amide formed between -COOH groups of one molecule of an amino acid and -NH2 group of another molecule of the amino acid by the elimination of a water molecules. 
What are the common types of secondary structure of proteins?
Differentiate between globular and fibrous proteins.
Difference between globular protein and fibrous protein:
|
Fibrous protein |
Globular protein
|
|
1.It is a fibre-like structure formed by the polypeptide chain. These proteins are held together by strong hydrogen and disulphide bonds |
1. The polypeptide chain in this protein is folded around itself, giving rise to a spherical Structure.
|
|
2. It is usually insoluble in water, but soluble in strong acids and bases. |
2. It is usually soluble in water, acids, bases and salts.
|
|
3. They have comparatively stronger intermolecular forces of attraction. |
3. They have weak intermolecular hydrogen bonding. |
|
4. Example: Collagen, fibroin, myosin, hair, skin,silk, wool, etc. |
4. Egg, albumin, casein of milk, insulin. |
How do you explain the amphoteric behaviour of amino acids?
In aqueous solution, the carboxyl group of an amino acid can lose a proton and the amino group can accept a proton to give a dipolar ion known as zwitter ion.
Therefore, in zwitter ionic form, the amino acid can act both as an acid and as a base. Thus, amino acids show amphoteric behaviour.
What is the effect of denaturation on the structure of proteins?
Denaturation of proteins: Proteins are very sensitive to the action of heat, change of pH, presence of electrolytes and radiations (particularly of short wavelength). Whenever proteins are subjected to such changes in the surroundings, they undergo some structural changes leading to disruption of three dimensional structure. This causes permanent loss of activity to proteins. Disruption of the native conformation of protein, by changing its environment, resulting in loss of its biological activity, is known as denaturation of proteins.
How are vitamins classified? Name the vitamin responsible for the coagulation of blood.
Vitamins are classified into two groups depending upon their solubility in water or fat.
i) Fat soluble vitamins: Vitamins which are soluble in fat and oils but insoluble in water. These are Vitamins A, D, E, and K.
ii) Water soluble vitamins: Vitamins which are soluble in water. These are B group vitamin and vitamin C.
Vitamin K is responsible for the coagulation of blood.
Why are vitamin A and vitamin C essential to us? Give their important sources.
(i) The chemical name of vitamin A is retinol.
The deficiency of vitamin A leads to xerophthalmia and night blindness. Important Sources of Vitamin ‘A’ : Milk, butter, egg, fish, and fish oil (Cod liver oil). It can also be synthesised in the body from carotenoids present in carrots, tomatoes, ripe mangoes etc. Carotenoids are the precursors of vitamin A.
(ii) The chemical name of vitamin C is ascorbic acid. The deficiency of vitamin C leads to scurvy.
Important Sources of Vitamin C: Citrus fruits (oranges, lemon, grape fruit, lime etc.), amla, cabbage, guava etc.
What are nucleic acids? Mention their two important functions.
Nucleic acids are biomolecules found in the nuclei of all living cells, as one of the constituents of chromosomes. Nucleic acids composed of a phosphoric acid group, a carbohydrates, and two purines and pyrimidines.There are mainly two types of nucleic acids − deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are also known as polynucleotides as they are long-chain polymers of nucleotides.
Fuctions:
(i) DNA is responsible for the transmission of inherent characters from one generation to the next. This process of transmission is called heredity.
(ii) Nucleic acids (both DNA and RNA) are responsible for protein synthesis in a cell. Even though the proteins are actually synthesised by the various RNA molecules in a cell, the message for the synthesis of a particular protein is present in DNA
What is the difference between a nucleoside and a nucleotide?
Nucleosides:
1. It contains only two basic components of nucleic acids, i.e., a pentose sugar and a nitrogenous base.
2. During their formation, 1-position of the pyrimi-dine or 9-position of the purine is linked to C, of the sugar (ribose or deoxyribose) by a β-linkage.
Nucleotides:
1. It contains all the three basic components of nucleic acids, i.e., a phosphoric acid group, a pentose sugar and a nitrogenous base.
2. These are formed by esterification of one of the hydroxyl groups (usually C5—OH of the sugar part) of the nucleoside with phosphoric acid.
The two strands in DNA are not identical but are complimentary. Explain.
(i) DNA has double helical structure in which two strands are twisted about each other held in position by H-bonds between the bases.
(ii) The two bases guanine and cytosine are complementary bases of DNA. Similarly, adenine and thymine are also complementary bases of DNA.
iii) If one of these bases is located on one chain of DNA, its complementary base is hydrogen bonded to it on the other chain. This means that the guanine base present on one chain of DNA is hydrogen bonded to its complementary base, cytosine present on the other chain. Similarly, adenine is hydrogen bonded to thymine on the other chain.
The two strands in DNA are not identical but are complimentary. Explain.
(i) DNA has double helical structure in which two strands are twisted about each other held in position by H-bonds between the bases.
(ii) The two bases guanine and cytosine are complementary bases of DNA. Similarly, adenine and thymine are also complementary bases of DNA.
If one of these bases is located on one chain of DNA, its complementary base is hydrogen bonded to it on the other chain.
This means that the guanine base present on one chain of DNA is hydrogen bonded to its complementary base, cytosine present on the other chain. Similarly, adenine is hydrogen bonded to thymine on the other chain.
| DNA | RNA |
| 1.DNA exists as double helix. | 1. RNA exists-as single chain. |
| 2. It is high polymer containing 2500 to 5000 nucleotides. | 2. It is relatively smaller polymer containing 75 to 1200 nucleotides. |
| 3.In DNA. the sugar is deoxyribose. | 3.In RNA the sugar unit is ribose. |
| 4. The base units in DNA are adenine, guanine, cytosine and thymine. | 4. The base units in RNA are adenine, guanine, cytosine and uracil. |
| 5.Uracil is absent in DNA. | 5. Thymine is absent in RNA. |
| 6. The hydrolysis products of DNA are phosphoric acid, deoxyribose, the bases A, G, C and T. |
6. The hydrolysis products of RNA are phosphoric acid, ribose and bases A.G, C and U. |
Compare α-D glucose with β-D glucose.
| α-D glucose | β-D glucose |
| 1.It is prepared by crystallization from cold aqueous solution. | 1.It is prepared by crystallisation from hot saturated aqueous solution. |
| 2.It melts at 419 K. | 2.It melts at 421 -423 K |
| 3. Specific rotation of freshly prepared aqueous solution is 113°. | 3.Specific roation of freshly prepared aqueous solution is 19°. |
The sequence in which the amino acids are arranged in a protein is called the primary structure of protein. The primary structure of protein determines its function and is critical to its biological activity. The change of just one amino acid in the sequence can alter its biological activity.
Secondary structure of proteins refers to the arrangement of polypeptide chains which arises as a result of hydrogen bonding. It arises due to regular folding of the back bone of polypeptide chain. It is two types.
(a) α-helix-Globular protein have α-helix structure.
(b) β-pleated-fibrous proteins have α-pleated structure.
What are the different types of RNA found in the cells of organisms? State the functions of each type.
There are three types of RNA found in the cells:
(i) Messenger RNA (mRNA): It provides a template for assembling amino acids in polypeptide chains. It carries the information transmitted from DNA.
(ii) Transfer RNA (tRNA): It carries the amino acids to mRNA template and also helps the mRNA to recognise the amino acids. Thus, tRNA molecules serve both as carrier of amino acids and interpreter of genetic code.
(iii) Ribosomal RNA (rRNA): It is an integral part of ribosomes that also takes part in protein synthesis. About 75% of cellular component of RNA is r-RNA.
What are nucleic acids? Explain their functions in the synthesis of proteins.
Nucleic acids are biomolecules found in the nuclei of all living cells, as one of the constituents of chromosomes.Nucleic acids are consist of a sugar unit, a phosphate group and a nitrogen base unit. These contain two type of bases:
(i) Pyrimidine bases.
(ii) Purine bases.
These are two types of sugar units in nucleic acids:
(i) Ribose.
(ii) Deoxyribose.
Nucleic acids are also known as polynucleotides as they are long-chain polymers of nucleotides.
Depending upon the type of sugar unit, there are two types of nucleic acids:
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Two main functions of nucleic acids are:
(i) DNA is responsible for the transmission of inherent characters from one generation to
the next. This process of transmission is called heredity.
(ii) Nucleic acids (both DNA and RNA) are responsible for protein synthesis in a cell.
Even though the proteins are actually synthesised by the various RNA molecules in a
cell, the message for the synthesis of a particular protein is present in DNA.
Name the deficiency diseases caused due to lack of the vitamin A, C, E, B1, B12 B6and K.
| Name of Vitamin | Deficiency disease |
| Vitamin A | Xerophthalmia i.e., hardening of cornea of eye. |
| Vitamin C | Scurvy |
| Vitamin E | Sterility |
| Vitamin B1 | Beri-beri (a disease of nervous system) |
| Vitamin B12 | Pemicious Anaemia |
| Vitamin B6 | Bevere dermatitis, convulsions. |
| Vitamin K | Hemorrhagic conditions. |
State differences between α-helix and β-pleated sheet structure.
| α-helix structure | β-pleated structure |
| 1. In α-helix. the peptide chains are coiled upto form helix which is right handed involving hydrogen bonding. | 1.The peptide chains lie side by side held together by inter molecular hydrogen bonding. |
| 2. Myosin, keratin and wool have α-helix structure. It acquires coil shape. |
2. Silk has β-pleated structure. It acquires streched sheet structure. |
State differences between primary and secondary structure of a protein.
|
Primary structure |
Secondary structure |
|
1. The sequence in which amino acids are arranged in a protein is called primary structure. It involves covalent bond.
|
1. The polypeptide chain gets folded due to intermolecular hydrogen bonding forming α-helix and β-pleated structure having polypeptide chains lie side by side involving inter molecular hydrogen bonding. |
State difference between Enzymes and Co-enzymes.
| Enzymes | Co-enzymes |
| 1. They are biological catalysts which are required to catalyse biochemical reaction, e.g. amylase,streptokinase, maltose. | 1. They are non- proteinous part which increase the activity of enzymes e.g., metal ion like, Mg2+, Zn2+, Mn2+, Na+, K+ or small molecules are called co-enzymes. |
| 2. All enzymes are proteins. | 2. Co-enzymes are non-proteinous. |
Name the water insoluble fraction of starch. Name the monomer of this ?
Amylopectin is a water insoluble fraction of starch.It is a polymer of alpha-glucose.
What do you mean understand by tertiary structure of proteins? Mention the forces involved informing these structures.
Tertiary structure of proteins : When the polypeptide chain with its secondary structure is further folded and twisted about itself a tertiary structure is formed. The tertiary structure of a protein adopts coiled compact structure of varying size and shape. The various forces involved in forming tertiary structures are,
(i) Hydrogen bonding.
(ii) Disulphide bridge.
(iii) Ionic or salt bridge.
(iv) Hydrophobic interaction.
Mention two structural differences between amylopectin and cellulose.
|
Amylopectin |
Cellulose |
|
1. It has a branched chain structure. |
1. It is a linear polymer. |
|
2. It is made of α-glucose units. |
2. It is made of β-glucose units. |
Name the product obtained on complete hydrolysis of DNA. Enumerate the structural differences between DNA and RNA. In what way is a nucleotide different from a nucleoside? Illustrate with examples.
The products of complete hydrolysis of DNA are:
(i) a pentose sugar
(ii) two types of heterocyclic nitrogenous bases.
(iii) phosphoric acid
The structural differences between DNA and RNA are:
(i) DNA has deoxyribose while RNA has ribose sugar.
(ii) DNA contains thymine and RNA has uracil.
(iii) DNA is double stranded while RNA is single stranded.
Nucleosides: The N-glycosides of purine or pyrimidine bases with pentose sugars are known as nucleosides.
Nucleotides: A nucleotide is a phosphate ester of nucleoside and consists of a purine or pyrimidine base, the 5-carbon sugar and one or more phosphate groups.
Nitrogen Base + Sugar + Phosphate = Nucleotide
What are nucleic acids? Explain their role in replication.
Nucleic acids are biomolecules which are present in the nucleus of living cells. There are two types of nucleic acids namely DNA (deoxyribo nucleic acid) and RNA (ribonucleic acid). The nucleic acids direct the synthesis of protein and are responsible for genetic information.
The process by which identical DNA molecules are synthesized from DNA molecules is called replication. As the cell divides the two strands of DNA are produced zip by zip from the double helix. These strands act as templates for the synthesis of new strands. The new strand is complementary to its parent strand. Now, the parent strand joins the new complementary strand and a double stranded helix of a new DNA is formed which is a true copy (replica) of the mother DNA. The second parent DNA strand also forms a new DNA with its complementary new DNA strand. In this way, two identical DNA molecules are formed from one DNA molecule.
Describe four functions of carbohydrates in living organism.
Functions of carbohydrates:
1. They support the plant structure, e.g., cellulose.
2. They produce energy necessary for functioning of living body and doing work.
3. They are used to store chemical energy in form of glycogen in liver. In case of emergency like fasting or illness, glycogen hydrolyses to glucose and thus supplies the necessary energy. Starch is main storage polysaccharide of plants.
4.Cellulose present in grass and plants act as a food for various grazing animals. These animals contain specific enzymes which can hydrolyse cellulose.
The tertiary structure of many proteins dissolved in water is disrupted by heating above 80°C, but primary structure is unaffected. Explain.
In the primary structure of proteins, the amino acid units are joined together by strong covalent bonds in a linear polymeric form. However, in the tertiary structure of proteins, the individual polypeptide chains are extensively coiled into globular like structure, with hydrogen bonds between carboxyl and amino acids.
When a protein dissolved in water is heated above 80°C rearrangement of secondary and tertiary structures occurs, since heat can cause disruption of these comparatively weaker forces of attraction. However, the primary structure is not affected, since it involves comparatively much stronger covalent bonds between various amino acid units.
How are glucose molecules joined together to make starch, glycogen and cellulose?
(i) Starch: Starch is a polymer of α-glucose and consists of two components, namely, amylose and amylopectin. Amylose is a linear polymer of α-D-glucose. It contains about 200 glucose units which are linked to one another through α-linkage involving C1 of one glucose unit with C4 of the other. Amylopectin, on the other hand, is a highly branched polymer.
(ii) Glycogen: It is a polymer of about thousand glucose units arranged in the form of highly branched chain.
(iii) Cellulose: Cellulose is a linear polymer of β-D-glycose in which C1 of one glucose unit is connected to C4 of the other as shown below
What are reducing and non-reducing sugars? What is the structural feature characterizing reducing sugars ?
Those carbohydrates which contain free aldehyde or ketonic group reduce Fehling’s solutions and Tollen’s reagent are called reducing sugar e.g., monosaccharides like glucose, fructose, galactose are reducing sugars.
Those carbohydrates which do not contain free aldehydes or ketonic group and do not reduce Fehling’s solution and Tollen’s reagent are called non-reducing sugars, e.g., maltose, lactose, sucrose.
Write the following about protein synthesis:
Name the location where protein synthesis occurs.
Write the following about protein synthesis:
How do 64 codons code for only 20 amino acids?
Write the following about protein synthesis:
Which of the two bases of the codon are most important for coding?
What deficiency diseases are caused due to lack of vitamins A, B, B6 and K in human diet?
Following are the deficiency diseases are caused:
i) Xerophthalmia or night-blindness is deficiency diseases of vitamin A.
ii) Beri-Beri is deficiency disease of vitamin B.
iii) Nervous disturbance (convulsion), severe dermatitis is caused by deficiency of vitamin B6.
iv) Haemophilia is caused by deficiency of vitamin K.
Draw open chain structure of aidopentose and aldohexose. How many asymmetric carbons are present in each?
Draw simple Fisher projections of D-and L-glucose. Are these enantiomers?
What type of linkages are responsible for the formation of:
(i) Primary structure of proteins.
(ii) Cross linking of polypeptides chains.
(iii) α-Helix formation
(iv) β-sheet structure.
(i) Peptide bonds.
(ii) Internal Hydrogen bonds
(iii) All possible hydrogen bonds.
(iv) Intermolecular Hydrogen bonds.
Which forces are responsible for the stability of α-helix? Why is it named as 3.6 helix?
The stability of alpha –helix structure is due to intramolecular of H-bonding between –NH- and –CO- groups of the same polypeptide chain. The alpha-helix is termed as 3.613 helix as each turn of the helix has nearly 3.6 amino acids and the hydrogen bonding leads to the formation of a 13-membered ring.
Answer the following queries about proteins:
How are proteins related to amino acids?
Answer the following query about proteins:
How are oligopeptides different from polypeptides?
Answer the following query about proteins:
When is a protein said to be denatured?
What is mutation? What are the consequences of mutation?
Any change in the base sequence of DNA which leads to the synthesis of proteins with altered amino acid sequence is called mutation.
Consequence of mutations: Mutation leads to the synthesis of proteins with an altered amino acid sequence. The proteins with changed sequences of amino acids may have no biological activity leading to the death of a cell.The defective gene may also cause abnormality or certain genetic diseases.
Explain the role of RNA in protein synthesis in a cell.
Describe briefly the following:
(i) Transcription (ii) Translation.
The genetic information coded in DNA in the form of specific base sequence has to be translated and expressed in the form of synthesis of specific proteins, which perform various functions in the cell. This is brought about in two steps called transcription and translation.
The transcription involves copying of DNA sequence into a complimentary RNA molecule called messenger RNA (m-RNA). The copying principle as in replication, but with the difference that the base A pairs with U in RNA.
During translation m-RNA directs protein synthesis in the cytoplasm of cell with the involvement of another type of RNA molecule called, transfer RNA (t-RNA) and the ribosomal particles.
Define the following terms: (i) Gene, (ii) Genetic code, (iii) Transcription, (iv) Translation, (v) Codon.
(i) Gene: Gene is a micelle protein which is considered to the unit of heredity.
(ii) Genetic Code: The heredity message stored in the arrangement of bases in the DNA molecules is called the genetic code.
(iii) Transcription: The way the code on DNA is copied to give the complimentary code on RNA is called transcription.
(iv) Translation: The way the four base code in nuclei acids is turned into a 20 unit code needed to specify the amino acid sequence in protein during synthesis is called translation.
(v) Codon: The three base sequence on a mRNA molecule that specifies the amino acids in a protein is called a codon.
List three functions of the nucleotides in a cell.
Function of nucleotides:
(i) Nucleotides are the monomer units of nucleic acids.
(ii) Some of the nucleotides act as coenzymes.
(iii) Each codon is made up of three nucleotides, hence they are helpful in the synthesis of any specific protein.
What is the effect of pH on the activity of enzymes?
Enzymes are highly sensitive to a change of pH value. Since enzymes are proteins, pH change greatly affect the ionic character of amino and carboxylic acid groups on the protein surface. This change affects the catalytic nature of an enzyme also. The enzymes function within a narrow range of pH value. For example,
Enzyme Pepsin Ptyalin Trypsin pH range 1.8 to 2.2 5.6. to 6.6 7.5. to 8.3
The low or high pH value can cause considerable denaturation of the protein and hence makes enzyme protein inactive.
The two samples of DNA, A and B have melting temperatures 340 and 350K respectively. Draw conclusion from this data regarding their base content.
What are polysaccharides? Name one of them. How is it important to us?
Polysaccharides are carbohydrates which on hydrolysis gives hundreds or even thousands of monosaccharides units. Cellulose is an example of polysaccharide.
Cellulose is an example of polysaccharide. Cellulose is important to us in the following ways:
(i) It is used in the manufacture of rayon and gun cotton (explosive).
(ii) It is used in the manufacture of cellotape and cellophone paper.
(iii) It is used in the manufacture of nitrocellulose (used as rocket propellant).
Give any two reactions of glucose to show the presence of an aldehyde group.
How will you show the presence of,
(i) primary alcoholic group.
(ii) Six carbon atoms in a straight chain in glucose.
A tipeptide on complete hydrolysis give glycine, alanine and phenyl alanine. Using three letter symbols, write down the possible sequences of the tripeptide.
A tripeptide is a peptide obtained by the condensation of three amino acids. The possible combinations of tripeptide obtained from glycine, alanine and phenylalanine are:
(i) Gly-Ala-Phe
(ii) Gly-Phe-Ala
(iii) Ala-Gly-Phe
(iv) Ala-Phe-Gly
(v) Phe-Ala-Gly
(vi) Phe-Gly-Ala.
If two amino acids: alanine and phenyl alanine react together, how many possible dipeptides can be formed? Write down the structures and names of each one. Also, write their names using three and one letter abbreviation for each amino acids.
Name: Phenylalanine
Three letter name is Phe -Ala one letter abbreviation is F—A.
Which bonds in the backbone of a peptide can rotate freely and which cannot? Give reasons.
Name the purine and pyrimidine bases present in DNA and RNA. Give the structure of any one of the pyrimidine base.
|
DNA |
RNA |
|
|
Purine Bases Pyrimidine Bases |
Adenine (A) Thymine (T) |
Adenine (A) Uracil (U) |
Structure of Uracil (pyrimidine base)
State the important features of the genetic code.
The genetic code has the following important features:
(i) It is universal.
(ii) It degenerates, i.e., more than one codon code for an amino acids.
(iii) It is commaless.
(iv) The third base of the codon is less specific.
Which vitamin is called ascorbic acid? What are its physiological functions? Which disease is caused by the deficiency of this vitamin?
Vitamin C is called ascorbic acid. Its physiological functions are:
(i) It improves appetite.
(ii) It helps in curing cold.
(iii) It helps in the healing of wounds and cuts.
(iv) It helps in the growth of good teeth.
The deficiency of this vitamin causes a disease called scurvy. This causes swelling and bleeding of gums, as well as pains in muscles and joints.
A vitaminoses is defined as the condition of vitamin deficiency. A lack of one or more vitamins leads to characteristic deficiency symptoms in man. Multiple deficiencies are caused by the lack of more than one vitamin.
The deficiency disease caused by lack of vitamin A is night blindness, and retarded growth. The deficiency disease caused by lack of vitamin K is increased time of blood clottings and hemorrhagic condition.
Explain the following:
Glucose responds Fehling solution and osazone, it does not react with Schiff’s base and sodium bisulphite.
Explain the following:
Glucosides react neither with Fehling solution nor with Tollen's reagent. They also do not allow mutarotation.
Explain the following:
Although fructose does not have an aldehydic group, it reacts with Fehling solution.
What is melting temperature (Tm) of DNA? A DNA molecule with more number of GC base pairs than AT base pairs has higher Tm than the one with lesser number of GC base pairs than AT base pairs. Explain why?
The temperature at which two strands of DNA separates completely is known as its melting temperature. It is specific for each specific sequence.
A DNA molecule with more number of GC base pairs than AT base pair has higher melting temperature because each GC pair contains three hydrogen bonds, while each AT base pair contains two hydrogen bonds.Therefore, more number of hydrogen bonds are present in DNA molecule with more GC pairs than AT pair.
What are forces holds the two strands of DNA together in a double-helix structure? Draw structure to show the bonding between adenine and thymine, and between guanine and cytosine.
Hydrogen bonding holds the two strands of DNA together in a double-helix structure.
‘A’ pairs up with ‘T’ via two hydrogen bonds while G pairs up with C via three hydrogen bonds.
'DNA replication is semi-conservative'. Explain.
What is transcription with reference to protein synthesis? How does it take place?
Transcription means copying the sequence of bases from DNA on messenger RNA (m-RNA). The copying of DNA sequence into m-RNA proceeds according to the same base pairing principle as in replication but differ in the following two respects:
(i) During m-RNA synthesis, the DNA double helix structure opens up and the ribonucleotides assemble along the uncoiled strand of DNA.
(ii) The base adenine (A) in DNA strand pair up with the uracil (U) in RNA.
After transcription, the m-RNA-DNA double helix separates. The m-RNA detaches itself and migrates to cytoplasm, while the DNA returns to its double helix structure.
Define enzymes. How do enzymes differ from ordinary chemical catalysts? Comment on the specificity of enzyme action. What is the most important reason for their specificity? Explain the mechanism of enzyme catalysis.
Enzymes are biocatalyst produced by the living cells which catalyse many biochemical reactions in animals and plant bodies. Enzymes are protein substances.
Enzymes differ from ordinary chemical catalysts in the following ways:
(i) Enzyme catalyst the reaction by about million times faster than the normal chemical catalysts.
(ii) Enzymes are very specific in their action. Each biochemical reaction requires a particular enzyme for it.
(iii) Enzymes work under milk conditions of temperature and at specific pH.
Specificity of enzyme action : Enzymes are extremely specific; Each reaction is generally catalyzed by a particular enzyme. For example, hydrolysis of urea is catalysed by only urease and none of the several thousand other enzymes present in the cell catalyse this reaction.
The specificity of enzymes results from the fact that each enzyme has a specific active site one its surface. When the reactant molecules, called the substrates of the reaction bind at the active site, a chemical change is initiated. In most of the cases, substrates bind to the active site through inter-molecular forces like H-bonds, dipole forces and other weak attraction.
Mechanism of enzymatic reaction involves four stages:
(i) The formation of complex between enzyme and substrate.
(ii) The conversion of this complex to an enzyme-intermediate complex
(iii) Further conversion of El to a complex between enzyme and product (EP)
(iv) The dissociation of the enzyme-product, leaving the enzyme unchanged
What are the building blocks (repeat units) of proteins? Describe the structure of protein.
A protein is a high polymer on hydrolysis it yields amino acids. Thus, amino acids are the monomeric units of all proteins. In a molecule of protein, the amino acid residues are joined by peptide bonds. Therefore, proteins are also called condensation products of amino acids or polyamide.
Structure of proteins: (a) Primary structure: Primary structure is the combination of amino acids in a proper sequence through peptide bonds.
(b) Secondary structure: In many proteins, polypeptide chain gets coiled up to form α-helix which is right handed and is called α-helix. In the helix each NH group is hydrogen bonded to the carbonyl oxygen of the third amino acids residue from it. It is this hydrogen bonding between different parts of the same chain which holds the helix together. Some proteins have β-pleated structure. This is also called β-sheet structure. In the sheet arrangement two peptide chains lie side by side and are joined via hydrogen bonds.
Fig. (a) Helical structure (b) The peptide
backbone in a helical structure.
Fig. β-pleated sheet structure of a protein
(c) Tertiary structure: The peptide chains with its secondary may be further folded and twisted about itself forming many structural coils of diverse sizes or shapes. They, brings some distant amino acids residues close to each other. Tertiary structures are held and stabilized by : (i) hydrophobic interactions, (ii) hydrogen bonds, (iii) Van der Waals forces and (iv) disulphide linkages between two side chains.
(d) Quaternary structure: This defines the degree of polymerization of protein unit. Both fibrous and globular proteins may contain one or more polypeptide chains. In case of fibrous protein these are called monomeric while in case of globular these are referred to as oligomeric. The individual peptide chains of an oligomeric protein are called promoters. These promoters may be same or different but are held together by weak binding force.
What do you mean by Zwitter ions and isoelectric points of amino acids?
The globular protiens are stabilised by __________ and van der Waal's forces.
hydrogen bonding.
A.
Glucose, maltose and lactose are examples of reducing sugars.
B.
Glucose and fructose both forms the same osazone.C.
On hydrolysis, sucrose yields a mixture of D(+) glucose and D(-) fructose.D.
In disaccharides, two monosaccharides are joined together by glycoside bonds.E.
The amino acids which are part of proteins have L-configuration.A.
The protein part of an enzyme is called coenzyme.
B.
Table sugar contains fructose.C.
Many vitamins are synthesized in the human body.D.
All α-amino acids that make up proteins are in L-configuration.E.
Proteins constitute the genetic material of the cell.Cellulose is a polymer of
A.
β-D (+) glucoseWhich of the following monosaccharide is pentose?
Glucose
Fructose
Arabinose
Galactose
C.
Arabinose
Sucrose is the disaccharide which on hydrolysis give mixture of glucose and fructose.
C12H22O11 + H2O ---> C6H12O6 + C6H12O6
sucrose glucose fructose
Why is cellulose in our diet not nourshing?
Cellulose in our diet is not nourishing as we do not have an enzyme capable of breaking cellulose molecules into monosaccharides.
Name one important function of nucleic acids in our bodies.
Nucleic acids are known as polynucleotides as they are long-chain polymers of nucleotides.
Two main functions of nucleic acids are:
(i) DNA is responsible for the transmission of inherent characters from one generation to the next. This process of transmission is called heredity.
(ii) Nucleic acids (both DNA and RNA) are responsible for protein synthesis in a cell.
Even though the proteins are actually synthesised by the various RNA molecules in a cell, the message for the synthesis of a particular protein is present in DNA.
Give structural difference is there between α-glucose and β-glucose?
Structural difference between α-glucose and β-glucose.
How do amino acids from proteins?
Amino acids are linked together by peptide bonds, thereby forming a long chain. Peptide bonds are formed by a biochemical reaction that extracts a water molecule as it joins the amino group of one amino acid to the carboxyl group of a neighbouring amino acid and hence forming a long chain of the protein.
Define mutation.
Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.
What is nucleotide?
A nucleotide is a phosphate ester of nucleoside and consists of a purine or pyrimidine base, the 5-carbon sugar and one or more phosphate groups.
Nucleotide =Base+Sugar+Phosphate
What type of bonding occurs in β-pleated structure of proteins?
Intermolecular hydrogen bonding occurs in the β-pleated structure of proteins
What is meant by primary structure of proteins?
The primary structure of a protein is the linear sequence of amino acids.The amino acids in the primary structure are held together by covalent bonds, which are made during the process of protein synthesis (translation).
Differentiate between aldose and Ketose ?
Aldose: This is a type of monosaccharide that contains an aldehyde group on its carbon skeleton. Generally, there is one aldehyde group per each monosaccharide molecule. The aldehyde group is a reactive chemical group denoted as (-CH=O). The chemical formula of aldose is written as Cn(H2O)n.
Ketose: Ketose is a type of monosaccharide where the carbon skeleton contains a ketone group.he ketone group is a reactive chemical group denoted as (-C=O). The simplest form of ketose is the sugar molecule made up of three Carbon atoms, the middle on with the ketone group. Just as aldoses, ketoses also have many stereogenic centres within the Carbon chain.
Enzymes act as catalysts for organic biochemical reactions.An example is the digestion of food, absorption of appropriate molecules and ultimately production of energy. This process involves a sequence of reactions and all these reactions occur in the body under very mild conditions. This occurs with the help of certain biocatalysts called enzymes.For example, the enzyme that catalyses hydrolysis of maltose into glucose is named as maltase.
How does DNA differ from RNA with respect to (a) Sugar and (b) base residues?
Deoxyribonucleic acid (DNA) and ribonucleic acid
(RNA).In DNA molecules, the sugar moiety is β-D-2-deoxyribose whereas, in RNA molecule, it is β-D-ribose.
DNA contains four bases viz. adenine (A), guanine (G), cytosine (C) and thymine (T). RNA also contains four bases, the first three bases are same as in DNA but the fourth one is uracil (U).
What are the different types of RNA found in the cells of organisms? What are their functions?
RNA molecules are of three types and they perform different functions. They are named as messenger
RNA (m-RNA), ribosomal RNA (r-RNA) and transfer RNA (t-RNA).
messenger RNA (m-RNA):
It carries the message, genetic information from DNA to the ribosomes where protein synthesis takes places. It reads the message in the group of three bases. The triplet of bases is called condon. m-RNA is a short -lived molecule.
Transfer RNA (t-RNA):
It acts as a carrier of amino acids. The t-RNA reads the codons expressed in m-RNA on the ribosomal particle. Each triplet of t-RNA thus carries the specific amino acid and transfers it to the proper location on the ribosomal particle. All t-RNA molecules have an L-shaped tertiary structure. The hydrophobic interaction is a major stabilising force in the tertiary structure of t-RNA.
Ribosomal RNA (r-RNA)
Ribosomal RNA (r-RNA) is an integral part of ribosomes that carries the genetic information from DNA to the ribosomes where actually the protein synthesis takes place.
What are vitamins? Classify them into water soluble and insoluble vitamins.
Vitamins are organic compounds required in the diet in small amounts to perform specific biological function for normal maintenance of optimum growth and health of the oragnism.
Vitamins are classified into two groups depending upon their solubility.
i) Fat soluble vitamins: Vitamins which are soluble in fat and oils but insoluble in water are kept in this group. For example Vitamin A, D, etc.
ii) Water soluble vitamins: vitamins which are soluble in water known as water soluble vitamins. For example vitamins B and vitmain C.
Explain mutarotation. Give its mechanism in case of D-glucose.
The spontaneous change in specific rotation of an optically active compound is called mutarotation.All reducing sugars undergo mutarotation. Glucose show mutarotation because during the formation of hemiacetal, another asymmetric carbon is produced (C-1) which can exist in two forms,
Explain the following:
Denaturation of proteins.
Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to physical change like a change
in temperature or chemical change like a change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of the protein.
Which one of the following is a disaccharide: Starch, Maltose, Fructose, Glucose ?
Maltose is a disaccharide, as it consists of two -D-glucose units. Starch is a polysaccharide, while glucose and fructose are monosaccharides
What is the difference between fibrous protein and globular protein?
|
Fibrous Proteins |
Globular Proteins |
|
They are fibre-like structures formed by polypeptide chains. Such proteins are held together by strong hydrogen and disulphide bonds. |
The polypeptide chains in these proteins are folded around themselves, giving these proteins a spherical structure. |
|
They are usually insoluble in water. |
They are usually soluble in water. |
|
They are structural proteins. For example, keratin is present in nails and hair, collagen is present in tendons and myosin is present in muscles. |
They are functional proteins. For example, most enzymes and some hormones like insulin. |
Write the name of vitamin whose deficiency causes bone deformities in children.
Deficiency of vitamin D causes bone deformities in children.
Which of the two components of starch is water soluble?
Starch contains two components: Amylose and Amylopectin. Amylose is the water-soluble component.
Deficiency of which vitamin causes night-blindness ?
Night blindness is caused due to the deficiency of vitamin A.
Name the base that is found in nucleotide of RNA only.
Uracil is the base that is found only in the nucleotide of RNA.
Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose?
The reaction of glucose with HI giving n-hexane suggests that all the six carbon atoms are linked in a straight chain, as shown in the reaction given below:
CHO-(CHOH)4-CH2OH 
CH3-CH2-CH2-CH2-CH2-CH2
What are three types of RNA molecules which perform different functions?
There are three different types of RNA molecules:
(i) Messenger RNA (mRNA)
(ii) Transfer RNA (tRNA)
(iii) Ribosomal RNA (rRNA)
What is meant by (i) peptide linkage (ii) biocatalysts?
(i) Peptide linkage: a peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). This is a dehydration synthesis reaction (also known as a condensation reaction) and usually, occurs between amino acid. Peptide linkage is responsible for the primary structure of protein.
A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). This is a dehydration synthesis reaction (also known as a condensation reaction) and usually, occurs between amine. Peptide linkage is responsible for the primary structure of protein
(ii) Biocatalysis is catalysis in living (biological) systems in which natural catalysts, such as protein enzymes, perform chemical transformations on organic compounds. For example DNA polymerization by DNA polymerase or Joining of DNA by DNA ligases.
Write any two reactions of glucose which cannot be explained by the open chain structure of glucose molecule.
The following two reactions of glucose cannot be explained by the open chain structure of glucose.
(i) Despite having the aldehyde group glucose does not give 2, 4-DNP test, Schiff’s test and it does not form the hydrogen sulphite addition product with NaHSO3.
(ii) The pentaacetate of glucose does not react with hydroxylamine indicating the absence of free- CHO group.
What is essentially the difference between α-form of glucose and β-form of glucose? Explain.
The α-form of glucose and β-form of glucose can be distinguished by the position of the hydroxyl group on the first carbon atom.
In open chain α-glucose, the hydroxyl group on the first carbon atom is towards the right whereas, in the closed ring α-glucose, the hydroxyl group on the first carbon atom is below the plane of the ring.
On the other hand, in open chain β-glucose, β-glucose, the hydroxyl group on the first carbon atom is towards the left whereas, in the closed ring β-glucose, the hydroxyl group on the first carbon atom is above the plane of the ring.
The structures of open and cyclic α-form and β-form of glucose can be drawn as follows.
Primary structure of proteins: Each polypeptide chain in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be the primary structure of proteins.
2. The secondary structure of proteins: The secondary structure of proteins refers to the shape in which a long polypeptide can exist. The two different secondary structures possible are α-helix structure and β-pleated sheet structure.
(i) α-Helical structure: In α-Helix structure, a polypeptide chain forms all possible hydrogen bonds by twisting into a helix with -NH group of each amino acid residue and hydrogen bonded to >C=O of an adjacent turn of the helix. The structure can be drawn as follows.
(ii) β-pleated structure: In a β-pleated structure, all peptide chains are stretched out to nearly maximum extensions and then laid side by side which are held together by intermolecular hydrogen bonds.
(i) Write the product obtained when D-glucose reacts with H2N - OH.
(ii) Amino acids show amphoteric behaviour. Why?
(iii) Why cannot vitamin C be stored in our body?
(i) When D-glucose reacts with NH2OH, an aldoxime is formed.
(ii) In aqueous solutions, the carboxyl groups of amino acids lose a proton. Amino groups of amino acids, on the other hand, accept a proton, giving rise to a dipolar ion known as zwitter ion.
This is neutral, but contains both positive and negative charges. In the zwitter ionic form, amino acids show amphoteric behaviour as they react with both acids and bases.
(iii) Vitamin C is water soluble and is readily excreted in urine. Hence, it cannot be stored in our body.
Write the name of linkage joining two amino acids.
The linkage which joins the two amino acids is known as peptide linkage.
Shanti, a domestic helper of Mrs. Anuradha, fainted while mopping the floor. Mrs. Anuradha immediately took her to the nearby hospital where she was diagnosed to be severely ‘anaemic’. The doctor prescribed an iron rich diet and multivitamins supplement to her. Mrs. Anuradha supported her financially to get the medicines. After a month, Shanti was diagnosed to be normal.
(i) What values are displayed by Mrs. Anuradha?
(ii) Name the vitamin whose deficiency causes ‘pernicious anaemia’.
(iii) Give an example of a water soluble vitamin.
(i) Mrs. Anuradha displayed values like concern, care and help by being with her domestic helper in her unfortunate moments.
(ii) Deficiency of Vitamin B12 causes ‘Pernicious anaemia’.
(iii) B group vitamins and Vitamin C are water soluble vitamins.
Write a reaction which shows that all the carbon atoms in glucose are linked in a straight chain.
When glucose is heated with an excess of Hl, it gives n-hexane.
Define the following as related to proteins:
(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation
(i) Peptide linkage:
The amide formed between -COOH group of one molecule of an amino acid and –NH2 group of another molecule of the amino acid by the elimination of a water molecule is called a peptide linkage.
(ii) Primary structure:
The primary structure of a protein refers to the specific sequence in which various amino acids are present in it, i.e., the sequence of linkages between amino acids in a polypeptide chain. The sequence in which amino acids are arranged is different in each protein. A change in the sequence creates a different protein.
(iii) Denaturation:
In a biological system, a protein is found to have a unique 3-dimensional structure and a unique biological activity. In such a situation, the protein is called native protein. However, when the native protein is subjected to physical changes such as a change in temperature or chemical changes such as a change in pH, its H-bonds are disturbed. This disturbance unfolds the globules and uncoils the helix. As a result, the protein loses its biological activity. This loss of biological activity by the protein is called denaturation. During denaturation, the secondary and the tertiary structures of the protein get destroyed, but the primary structure remains unaltered.
One of the examples of denaturation of proteins is the coagulation of egg white when an egg is boiled.
(i) Write the name of two monosaccharides obtained on hydrolysis of lactose sugar.
(ii) Why Vitamin C cannot be stored in our body?
(iii) What is the difference between a nucleoside and nucleotide?
(i) Upon hydrolysis, lactose produces one molecule of D-glucose and one molecule of D-galactose..
(ii) Vitamin C is water-soluble in nature. It cannot be stored in the human body as it repeatedly gets eliminated through urine.
(iii)A nucleoside is formed by the attachment of purine or pyrimidine base to the 1- position of a pentose sugar.
On the other hand, a nucleotide is a unit formed by the attachment of nucleoside to phosphoric acid at the 5′-position of the sugar moiety.
i) Write the structural difference between starch and cellulose.
ii) What type of linkage is present in Nucleic acid ?
iii) Give one example each for fibrous protein and globular protein.
Write the main structural difference between DNA and RNA. Of the four bases, name those which are common to both DNA and RNA.
The structural differences between DNA and RNA are as follows:
|
DNA |
RNA |
||
|
1. |
The sugar moiety in DNA molecules is b-D-2 deoxyribose. |
1. |
The sugar moiety in RNA molecules is b-D-ribose. |
|
2. |
DNA contains uracil (U). It does not contain thymine (T). |
2. |
RNA contains thymine (T). It does not contain uracil (U). |
|
3. |
The helical structure of DNA is double-stranded. |
3. |
The helical structure of RNA is single-stranded. |
Write such reactions and facts about glucose which cannot be explained by its open chain structure.
(i) Aldehydes give 2, 4-DNP test, Schiff’s test, and react with NaHSO4 to form the hydrogen sulphite addition product. However, glucose does not undergo these reactions.
(ii) The pentaacetate of glucose does not react with hydroxylamine. This indicates that a free -CHO group is absent from glucose.
(iii) Glucose exists in two crystalline forms a and b. The a-form (m.p. = 419 K) crystallises from a concentrated solution of glucose at 303 K and the b-form (m.p = 423 K) crystallises from a hot and saturated aqueous solution at 371 K. This behaviour cannot be explained by the open chain structure of glucose.What are the products of hydrolysis of sucrose?
Hydrolysis of sucrose gives glucose and fructose as products.
Define the following terms as related to proteins:
(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation
(i) Peptide linkage: It is the amide formed between the −COOH and −NH2 groups of two amino acid molecules.
(ii) Primary structure of proteins: Proteins contain one or more polypeptide chains and each chain has amino acids linked with each other in a specific sequence. This sequence of amino acids represents the primary structure of proteins.
(iii) Denaturation: It is the loss of biological activity of proteins because of some physical changes like changes in pH and temperature, due to which the unfolding of globules and the uncoiling of helix take place.
Examples: Coagulation of egg white on boiling and curdling of milk.
After watching a programme on TV about the presence of carcinogens(cancer causing
agents) Potassium bromate and Potassium iodate in bread and other bakery products, Ritu a class XII student decided to aware others about the adverse effects of these carcinogens in foods. She consulted the school principal and requested him to instruct canteen contractor to stop selling sandwiches, pizza, burgers and other bakery products to the students. Principal took an immediate action and instructed the canteen contractor to replace the bakery products with some proteins and vitamins rich food like fruits, salads, sprouts etc. The decision was welcomed by the parents and students.
After reading the above passage, answer the following questions :
(i) What are the values (at least two) displayed by Ritu?
(ii) Which polysaccharide component of carbohydrates is commonly present in bread?
(iii) Write the two types of secondary structure of proteins.
(iv) Give two examples of water soluble vitamins.
(i) Concerned for the people.
Scientific temper and application of knowledge.
(ii) Starch ( amylose and amylopectin)
(iii) Two types of secondary structure of proteins are Alpha helices and Beta pleated sheets.
(iv) Vitamin C, Vitamin B1 and B2 are water soluble.
Define the following with an example:
Polysaccharides
Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages for example starch.
Define the following with an example:
Denatured protein
When a protein in its native form, is subjected to physical change like a change in temperature or chemical change like a change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix gets uncoiled and protein loses its biological activity. This is called denaturation of the protein.
Define the following with an example:
Essential amino acids
The amino acid which cannot be synthesised in the body and must be obtained from the diet are known as essential amino acid.
The 9 essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Write the product when D-glucose reacts with conc. HNO3
When D-glucose react with (conc.) Nitric acid, it forms Saccharic acid.
Amino acids show amphoteric behaviour. Why?
In aqueous solution, the carboxyl group of an amino acid can lose a proton and the amino group can accept a proton to give a dipolar ion known as zwitter ion.
Therefore, in zwitter ionic form, the amino acid can act both as an acid and as a base. Thus, amino acids show amphoteric behaviour.
Write one difference between α -helix and β -pleated structures of proteins.
α - helix: It has a polypeptide chain which forms all possible hydrogen bonds twisting it into a right-handed screw. (helix)
β - pleated: It has peptide chain which is stretched out to nearly maximum extension and then laid side by side which are held by intermolecular hydrogen bonds.
The absolute configuration of
is:
(2S, 3R)
(2S, 3S)
(2R, 3R)
(2R, 3S)
A.
(2S, 3R)
Which one of the following bases is not present in DNA?
Quinoline
Adenine
Cytosine
Thymine
A.
Quinoline
Quinoline is an alkaloid, it is not present in DNA. DNA has four nitrogen bases in adenine, guanine, cytosine and thymine
Synthesis of each molecule of glucose in photosynthesis involves
18 molecules of ATP
10 molecules of ATP
8 molecules of ATP
6 molecules of ATP
A.
18 molecules of ATP
6CO2 + 12NADP.2H + 18 ATP → C6H12O6 + 18 P +12NADP +18 ADP
Which of the following compounds can be detected by Molisch’s test?
Nitro compounds
Sugars
Amines
Primary alcohols
B.
Sugars
Molisch’s Test: when a drop or two of the alcoholic solution of α–naphthol is added to sugar solution and then conc. H2SO4 is added along the sides of the test tube, the formation of violet ring takes place at the junction of two liquids.
The presence or absence of hydroxy group on which carbon atom of sugar differentiates RNA and DNA.
1st
2nd
3rd
4th
B.
2nd
RNA and DNA has ribose and deoxyribose sugars, which differs in absence of hydroxy group at 2 nd carbon.
Biuret test is not given by
proteins
carbohydrates
polypeptides
urea
B.
carbohydrates
Biuret test is given by the compounds having peptide bond which is not present in carbohydrate. Biuret Test produces violet colour on addition of dilute CuSO4 to an alkaline solution of a compound containing peptide linkage.
Which of the following compounds will behave as a reducing sugar in an aqueous KOH solution?
A.
Ester in presence of Aqueous KOH solution give SNAE reaction so following reaction takes place
The two functional groups present in a typical carbohydrate are
-OH and -COOH
-CHO and -COOH
>C = O and - OH
-OH and -CHO
C.
>C = O and - OH
Carbohydrates are primarily hydroxyl carbonyl compound hence > C = O and –OH are present.
α-D-(+)-glucose and β-D-(+)-glucose are
conformers
epimers
anomers
enantiomers
C.
anomers
α - D (+) glucose and β - D (+) glucose are anomers.
The secondary structure of a protein refers to
α-helical backbone
hydrophobic interactions
sequence of α-amino acids
fixed configuration of the polypeptide backbone
A.
α-helical backbone
The secondary structure of proteins involves α − helical back bond and β − sheet structures. These structures are formed as a result of H-bonding between different peptide groups.
The term anomers of glucose refers to
isomers of glucose that differ in configurations at carbons one and four (C-1 and C-4)
a mixture of (D)-glucose and (L)-glucose
enantiomers of glucose
isomers of glucose that differ in configuration at carbon one (C-1)
D.
isomers of glucose that differ in configuration at carbon one (C-1)
The pyrimidine bases present in DNA are
cytosine and adenine
cytosine and guanine
cytosine and thymine
cytosine and uracil
C.
cytosine and thymine
Insulin production and its action in the human body are responsible for the level of diabetes. This compound belongs to which of the following categories?
A co- enzyme
An antibiotic
A hormone
An enzyme
C.
A hormone
Insulin is a hormone built up of two polypeptide chains.
Glucose on prolonged heating with HI gives
6-iodohexanal
n-Hexane
1-Hexene
Hexanoic acid
B.
n-Hexane
The reaction of glucose with HI giving n-hexane suggests that all the six carbon atoms are linked in a straight chain, as shown in the reaction given below:
In a protein molecule various amino acids are linked together by
peptide bond
dative bond
B.
peptide bond
Two amino acids on the protein are linked by a peptide bond. For example. Glycyllalanine is formed when carboxyl group of glycine combines with the amino group of alanine.
Which of the following statement is false?
Ca2+ ions are important in blood clotting
Ca2+ ions are not important in maintaining the regular beating of the heart.
Mg2+ ions are important in the green parts of plants
Mg2+ ions form a complex ATP
B.
Ca2+ ions are not important in maintaining the regular beating of the heart.
Ca2+ ions are very important for maintaining the regular heart beating.
The correct statement regarding RNA and DNA, respectively is
The sugar component in RNA is ribose and sugar component in DNA is 2' deoxyribose
The sugar component in RNA is arabinose and the sugar component in DNA is ribose
The sugar component in RNA is 2'-deoxyribose and the sugar component in DNA is arabinose
The sugar component in RNA is arabinose and the sugar component in DNA is 2' deoxyribose.
A.
The sugar component in RNA is ribose and sugar component in DNA is 2' deoxyribose
In DNA, two helically twisted strands connected together by steps. Each strand consists of alternating molecules of deoxyribose at 2'-position and phosphate groups.
On another hand, in RNA, the pentose sugar has an identical structure with deoxyribose sugar except that there is an -OH group instead of -H on carbon atom2'. Hence it is only called ribose.
Which one given below is a non - reducing sugar?
Lactose
Glucose
Sucrose
Maltose
C.
Sucrose
sucrose is non-reducing sugar because it has one -CHO group.
The function of 'sodium pump' is a biological process operating in each and every cell of all animal. Which of the following biologically important ions is also a constituent of this pump?
Ca2+
Mg2+
K+
Fe2+
C.
K+
The sodium pump is also known as a sodium Potassium pump. This pump is important contributor to action potential produced by nerve cells. The process of moving sodium potassium ions across the cell membranes is active transport process involving the hydrolysis of ATP to provide the necessary energy.
Which one of the following statement is incorrect about enzyme catalysis?
Enzymes are mostly proteinous in nature
Enzyme action is specific
Enzymes are denaturated by ultraviolet rays and at high temperature
Enzymes are least reactive at optimum temperature
D.
Enzymes are least reactive at optimum temperature
Most of the enzymes have proteinous nature. They are highly specific and get denaturated by high temperature or UV rays. At optimum temperature, which is generally in between 25-35o, enzyme activity is maximum.
Deficiency of vitamin B1 causes the disease
convulsions
beri-beri
cheilosis
sterility
B.
beri-beri
Deficiency of vitamin B1 cause beri-beri in which they occur a loss of appetite and vigour, weak heart beat etc.
Which one of the following sets of monosaccharides forms sucrose?
α-D-glucopyranose and β-D-fructopyranose
B.
α-D-glucopyranose and β-D-fructofuranoseSucrose is composed of α-D-glucopyranose and β-D-fructofuranose units which are joined by α, β-glycosidic linkage between C-1 of the glucose unit and C-2 of the fructose unit.
Which one of the following statements is not true regarding (+) lactose?
(+) lactose is a β - glycoside formed by the union of a molecule of D (+) galactose
(+) lactose is a reducing sugar and does not exhibit mutarotation
(+) lactose, C12H22O11 contains 8 - OH groups
On hydrolysis (+) lactose gives equal amount of D (+) glucose and D (+) galactose
B.
(+) lactose is a reducing sugar and does not exhibit mutarotation
Which of the following is not a fat soluble vitamin?
Vitamin- B - complex
Vitamin -D
Vitamin -E
Vitamin -A
A.
Vitamin- B - complex
Vitamin - A, D and E are fat soluble vitamins whereas vitamin - B complex is a water soluble vitamin
Which of the statement about 'Denaturation' given below are correct?
Statements,
A) Denaturation of proteins causes loss of secondary and tertiary structures of the protein.
B) Denaturation leads to the conversion of double strand of DNA into single strand.
C) Denaturation affects primary structure which gets distroyed.
(B) and (C)
(A) and (C)
(A) and (B)
(A), (B) abd (C)
B.
(A) and (C)
During denaturation secondary and tertiary structures of protein destroyed but the primary structure remains to interact.
Which one of the following species does not exist under normal conditions?
(+)Sucrose
(+)Lactose
(+) Maltose
(-) Fructose
A.
(+)Sucrose
Reducing sugars that exist in hemiacetal and hemiketal forms, undergo mutarotation in aqueous solution.
Among the given carbohydrates, only sucrose is a non-reducing sugar as in it the hemiacetal and hemiketal groups of glucose and fructose are linked together through O-atom and thus, not free. Due to the absence of free hemiacetal or hemiketal group, sucrose does not exhibit mutarotation.
Fructose reduces Tollen's reagent due to
asymmetric carbons
primary alcoholic group
secondary alcoholic group
enolization of fructose followed by conversion to the aldehyde by base
D.
enolization of fructose followed by conversion to the aldehyde by base
In aqueous solution, fructose is enolized and then converted into aldehyde in basic medium. All aldehydes generally reduces Tollen's reagent thus fructose also reduces Tollen's reagent.
The segment of DNA, which acts as the instrumental manual for the synthesis of the protein is
nucleotide
ribose
gene
nucleoside
C.
gene
The segment of DNA Which acts as the instrumental manual for the synthesis of the protein is a gene. Every protein in a cell has a corresponding gene.
In DNA. the complimentary bases are
Adenine and thymine; guanine and cytosine
Adenine and thymine; guanine and uracil
Adenine and guanine, thymine: Guanine and uracil
Uracil and adenine; cytosine and guanine
A.
Adenine and thymine; guanine and cytosine
Deoxyribonucleic acid (DNA) has the purine bases adenine and guanine and pyrimidine bases thymine and uracil. According to base pairing rule adenine paired with thymine (A=T) and cytosine paired with guanine 
Which one of the following vitamins is water soluble?
vitamin - B
vitamin - E
vitamin - K
vitamin - A
A.
vitamin - B
Vitamins are classified as
(i) Fat soluble vitamin: A, D, E, K
(ii) Water soluble; Vitamin B complex and c S vitamin B is water soluble.
RNA and DNA are chiral molecules, their chirality is due to:
L -sugar component
chiral bases
chiral phosphate ester units
D -sugar component
D.
D -sugar component
RNA and DNA molecules have ribose and deoxyribose sugar respectively. Both are chiral, their chirality is due to D -ribose or deoxyribose sugar components.
During the process of digestion, the proteins present in food materials are hydrolysed in amino acids. The two enzymes involved in the process
are respectively:
amylase and maltase
diastase and lipase
pepsin and trypsin
invertase and zymase
C.
pepsin and trypsin
In the process of digestion, the proteins present in food material are hydrolysed to an amino acid. In this process two enzymes pepsin and trypsin are involved as follows:
The human body does not produce:
DNA
Vitamins
Hormones
enzymes
B.
Vitamins
The organic compounds other than carbohydrates proteins, which maintain normal growth and nutrition in the human body (but not produced in the human body) are called vitamins.
Which one of the following is a peptide hormone?
Glucagon
Testosterone
Thyroxin
Adrenaline
A.
Glucagon
Glucagon is a peptide hormone because it is peptide linkage is present.
Which of the following statements is not correct?
Insulin maintains sugar level in the blood of ahuman body
Ovalbumin is a simple food reserve in egg-white
Blood proteins thrombin and fibrinogen are involved in blood clotting
Denaturation makes the proteins more active
D.
Denaturation makes the proteins more active
Due to denaturation of proteins, globules unfold and helix get uncoiled and protein loses its biological activity.
The difference between amylose and amylopectin is
Amylopectin have 1 → 4 α-linkage and 1 → 6 α-linkage
Amylose have 1 → 4 α-linkage and 1 → 6 β-linkage
Amylose is made up of glucose and galactose
Amylopectin have 1 → 4 α-linkage and 1 → 6 β-linkage
A.
Amylopectin have 1 → 4 α-linkage and 1 → 6 α-linkage
In amylose the 1-4 glycosidic.
In amylopectin there is two linkage such as 1-6 glycosidic or 1-4 glycosidic.
Amylose and Amylopectin are polymers of α-D-glucose, so β link is not possible. Amylose is linear with 1 → 4 α-linkage whereas Amylopectin is branched and has both 1 → 4 and 1 → 6 α-linkages.
On hydrolysis of starch, we finally get
Glucose
Fructose
Both (a) and (b)
Sucrose
A.
Glucose
Starch is a polymer of D-glucose units, thus on hydrolysis it only gives glucose.
Sponsor Area
Sponsor Area
respectively of the sugar molecule
respectively of the sugar molecule
respectively of the sugar molecule
