9

Q1. Anti-parallel strands of a DNA molecule mean that

• 1) One strand turns anticlockwise
• 2) Phosphate groups at the start of two DNA strands (poles) are in opposite position
• 3) Phosphate groups of two DNA strands at their ends share the same position
• 4) One strand turns clockwise

Solution

Anti-parallel strands of a DNA molecule mean that phosphate groups at the start of two DNA strands (poles) are in opposite position.

Q2. Give one example of catabolic pathway.  

Solution

Example of the catabolic pathway: Degradation of glucose into lactic acid  

Q3. What is a chemical reaction?

Solution

The process of transformation of a substance in which old bonds are broken and new bonds are formed is called a chemical reaction.

Q4. Nitrogenous bases present in DNA

• 1) Adenine, guanine, cytosine, thymine
• 2) Guanine, uracil
• 3) Adenine, guanine, cytosine, uracil
• 4) Adenine, thymine, uracil

Solution

DNA contains four types of nitrogenous bases: Two double-ringed purines - adenine and guanine Two single-ringed pyrimidines - cytosine and thymine

Q5. Which is true about enzymes?

• 1) All proteins are enzymes.
• 2) All enzymes are vitamins.
• 3) All enzymes are not proteins.
• 4) All enzymes are proteins.

Solution

All enzymes are protein by nature. Amino acids join by peptide bonds and the molecule takes a three-dimensional conformation to form active sites.

Q6. Define substrate.

Solution

The chemical which is converted into a product during an enzyme-catalysed reaction is called a substrate.

Q7. Classify the following into nitrogen bases, nucleosides and nucleotides:     Guanine   Adenosine   Thymidylic acid   Uridine

Solution

Nitrogenous Base     Nucleoside     Nucleotide     Guanine     Adenosine Uridine     Thymidylic acid        

Q8. Enzymes with slightly different molecular structure but performing identical activity are

• 1) Isoenzymes
• 2) Apoenzymes
• 3) Holoenzyme
• 4) Coenzymes

Solution

Enzymes which have minor differences in their molecular structure but perform identical catalytic activity are called isoenzymes or isozymes.

Q9. Hydrogen bonds present between cytosine and guanosine are  

• 1) 1  
• 2) 3  
• 3) 2  
• 4) 4  

Solution

Cytosine and guanine are joined by three hydrogen bonds.     Adenine and thymine are joined by two hydrogen bonds.  

Q10. Vitamin B₂ is a component of coenzyme  

• 1) TPP  
• 2) NAD  
• 3) FMN/FAD  
• 4) Pyridoxal phosphate  

Solution

Vitamin B₂ is also called riboflavin.     FMN/FAD are composed of flavin, ribitol sugar and phosphate molecules.     Flavin is derived from riboflavin.  

Q11. A functional protein is  

• 1) Enzyme  
• 2) Ossein  
• 3) Collagen  
• 4) Vitamin  

Solution

An enzyme functions to regulate metabolism in cells. Enzymes are thus termed functional proteins.  

Q12. Write two examples of the secondary metabolites for the following categories which are of commercial importance: Alkaloids Drugs

Solution

Alkaloids - Codeine, Morphine Drugs - Curcumin, Vinblastine

Q13. Glycogen is a homopolymer made of

• 1) Ribose units
• 2) Glucose units
• 3) Galactose units
• 4) Amino acids

Solution

Glycogen is a branched chain homopolymer. It consists of about 30,000 glucose units.

Q14. What are biomacromolecules?

Solution

Molecules which are found in the acid-insoluble fraction and have molecular weights above 10,000 dalton are called biomacromolecules.

Q15. Table sugar is

• 1) Sucrose
• 2) Lactose
• 3) Fructose
• 4) Glucose

Solution

Sucrose is commonly called table sugar. It is used as a sweetener in daily life in the form of sugar. It is a non-reducing sugar containing one fructose and one glucose molecule.

Q16. Enzymes are polymers of

• 1) Inorganic phosphate
• 2) Amino acids
• 3) Hexose sugar
• 4) Fatty acids

Solution

Enzymes are protein in nature. They are polymers of amino acids which form a three-dimensional tertiary structure.

Q17. A competitive inhibitor of succinic dehydrogenase is

• 1) Malate
• 2) α-Ketoglutarate
• 3) Oxaloacetate
• 4) Malonate

Solution

Succinate dehydrogenase oxidises succinate and forms fumarate. Malonate acts as a competitive inhibitor to succinate by competing with it for binding to the active site on the enzyme succinate dehydrogenase.

Q18. What is the dynamic state of body constituents?

Solution

The flow of metabolites through a metabolic pathway at a definite rate and in a definite direction is called the dynamic state of body constituents.

Q19. Name the polysaccharide which is found in the exoskeleton of arthropods.

Solution

Chitin

Q20. The most abundant element in living beings is

• 1) Carbon
• 2) Nitrogen
• 3) Oxygen
• 4) Hydrogen

Solution

Carbon forms the backbone of all the important molecules which make up a living cell - nucleic acids, carbohydrates, fats and proteins. Thus, it is the most abundant element in living forms.

Q21. Glycogen is a polymer of

• 1) Sucrose
• 2) Galactose
• 3) Fructose
• 4) Glucose

Solution

Glycogen is a polymer of glucose containing 30,000 glucose units. It is a branched chain. Glucose is joined by 1-4 α glycosidic bonds. 

Q22. Which of the following is a structural subunit of DNA?

• 1) Protein
• 2) Carbohydrate
• 3) Nucleotide
• 4) RNA

Solution

Nucleotides are structural sub-units of DNA. Nucleotides join with each other through phosphodiester bonds to form a polynucleotide.

Q23. In DNA, hydrogen bonds and base pairing occur between which pairs?  

• 1) A-T, C-G  
• 2) A-C, G-T  
• 3) A-G, C-T  
• 4) A-U, C-G  

Solution

In DNA, hydrogen bonds and base pairing occur between A and T and C and G.      

Q24. What is the other name given to B-DNA?

Solution

  The other name given to B-DNA is the Watson-Crick model.

Q25. Enzymes which catalyse the interconversion of optical, geometrical or positional isomers are

• 1) Isomerases
• 2) Ligases
• 3) Hydrolases
• 4) Lyases

Solution

Isomers are substances which have the same chemical formula but different optical, positional or geometric configuration. Isomerases catalyse the interconversion of isomeric substances by the rearrangement of molecules.

Q26. Nitrogen is an important component of

• 1) Carbohydrates
• 2) Proteins
• 3) Polyphosphates
• 4) Lipids

Solution

Proteins are polymers of amino acids. Nitrogen is an important component of amino acids. Proteins differ from carbohydrates and fats in having nitrogen as a component of its structure.

Q27. Which of the following groups contains all polysaccharides?  

• 1) Maltose, lactose and fructose  
• 2) Glycogen, sucrose and maltose  
• 3) Glycogen, cellulose and starch  
• 4) Sucrose, glucose and fructose  

Solution

Glycogen, cellulose and starch are polysaccharides.     Sucrose, maltose and lactose are disaccharides.     Glucose and fructose are monosaccharides.  

Q28. State the common feature found in all compounds of the acid pool.

Solution

The common feature found in all compounds of the acid pool is that they have molecular weights ranging from 18 to approximately 800 dalton.

Q29. State the normal blood glucose concentration in a healthy individual.  

Solution

The normal blood glucose concentration in a healthy individual is 4.5-5.0 mM.  

Q30. Uracil is present in RNA at the place of

• 1) Adenine
• 2) Cytosine
• 3) Guanine
• 4) Thymine

Solution

Uracil is a pyrimidine present in RNA in place of thymine in DNA.

Q31. The simplest amino acid is

• 1) Glycine
• 2) Valine
• 3) Tryptophan
• 4) Arginine

Solution

Glycine is the simplest amino acid, with hydrogen as its R group.

Q32. Amino acids, as the name suggests, have both an amino group and a carboxyl group in their structure. In addition, all naturally occurring amino acids (those which are found in proteins) are called L-amino acids. From this, can you guess from which compound the simplest amino acid is made?  

• 1) Glycine  
• 2) Formic acid  
• 3) Phenol  
• 4) Methane  

Solution

The general structure of an amino acid is given below.     From this we can deduce that the simplest amino acids are derived from methane.        

Q33. Name the most abundant protein found in the animal world.

Solution

Collagen

Q34. Which is wrong about nucleic acids?

• 1) Length of one helix is 45A° in B-DNA
• 2) One turn of Z-DNA has 12 bases
• 3) DNA is single stranded in some viruses
• 4) RNA is double stranded occasionally

Solution

Length of one helix or the pitch per turn of helix is 34A°, 25A° in A-DNA and 46A° in Z-model of DNA.

Q35. State the units used to express the concentration of biomolecules.

Solution

The units used to express the concentration of biomolecules are mols/cell and mols/litre.

Q36. Lactose is made of

• 1) Glucose + Glucose
• 2) Glucose + Galactose
• 3) Fructose + Fructose
• 4) Glucose + Fructose

Solution

Lactose is made of glucose and galactose joined by 1 and 4 carbon atoms. Lactose is present in milk.  

Q37. A segment of DNA has 120 adenine and 120 cytosine bases. The total number of nucleotides present in the segment is  

• 1) 120  
• 2) 240  
• 3) 60  
• 4) 480  

Solution

According to Chargaff’s rule, in DNA, the amount of adenine is always equal to that of thymine and the amount of guanine is always equal to that of cytosine.     A = T = 120 and C = G = 120     Thus, the total number of nucleotides in DNA is 480.  

Q38. Conjugated proteins containing carbohydrates as a prosthetic group are known as 

• 1) Glycoproteins
• 2) Chromoproteins
• 3) Lipoproteins
• 4) Nucleoproteins

Solution

Glycoproteins are conjugated proteins with a simple or complex sugar residue at their N-terminal end. They are found in egg white, mucin, IgG and heparin.  

Q39. Proteins perform many physiological functions. For example, some function as enzymes. Which one of the following represents an additional function which some proteins discharge?

• 1) Antibiotics
• 2) Pigments making colours of flowers
• 3) Pigments conferring colour to skin
• 4) Hormones

Solution

Hormones are chemical substances which are released in the body for regulation and metabolism in cells. Many hormones such as insulin and parathormone are proteinic in nature.

Q40. Give any one example of a coenzyme which acts as a cofactor.

Solution

Nicotinamide adenine dinucleotide (NAD)

Q41. The bacterial cell wall is formed of

• 1) Cellulose
• 2) Hemicellulose
• 3) Peptidoglycan
• 4) Glycogen
• 5) Both 1 and 2 above

Solution

The cell wall of bacteria is mainly composed of peptidoglycan. Peptidoglycan is a heteropolymer containing polysaccharide chains. These chains are crossed linked by peptides.

Q42. Many elements are found in living organisms either free or in the form of compounds. One of the following is not found in living organisms:  

• 1) Sodium  
• 2) Iron  
• 3) Magnesium  
• 4) Silicon  

Solution

Silicon is absent or found in negligible amounts in living organisms.  

Q43. Which one is correct base pairing for DNA molecule?

• 1) Adenosine-Thymine
• 2) Thymine-Guanine
• 3) Thymine-Uracil
• 4) Cytosine-Uracil

Solution

In a DNA molecule, adenosine pairs with thymine using two hydrogen bonds.

Q44. Cellulose, the most important constituent of the plant cell wall, is made up of

• 1) Unbranched chain of glucose molecules linked by α, 1, 4 glycosidic bond
• 2) Unbranched chain of glucose molecules linked by β, 1, 4 glycosidic bond
• 3) Branched chain of glucose molecules linked by α, 1, 6 glycosidic bond at the site of branching
• 4) Branched chain of glucose molecules linked by β, 1, 4 glycosidic bond in straight chain and α, 1, 6 glycosidic bond at the site of branching

Solution

Cellulose is made up of glucose monomers. It is an unbranched chain of glucose molecules linked by a β,1,4 glycosidic bond.

Q45. In the double helix model of DNA, how far is each base pair from the next base pair?

• 1) 2.0 nm
• 2) 0.34 nm
• 3) 34 nm
• 4) 0.034 nm
• 5) 3.4 nm

Solution

One turn of DNA double helix is 3.4 nm long. Each turn contains 10 base pairs. Thus, the distance between two base pairs in DNA is 0.34 nm.

Q46. Key and lock hypothesis of enzyme action was given by

• 1) Koshland
• 2) Buchner
• 3) Fischer
• 4) Kuhn

Solution

Emil Fischer suggested the lock and key hypothesis for enzyme action in 1894.

Q47. Enzymes increase the rate of biochemical reaction through  

• 1) Changing equilibrium  
• 2) Forming enzyme-product complex  
• 3) Forming reactant-product complex  
• 4) Lowering activation energy  

Solution

Enzymes increase the rate of biochemical reaction through lowering the activation energy.     By lowering the activation energy, it allows a large number of molecules to react at a time, and thus, the rate of chemical reaction increases.  

Q48. Which one contains four pyrimidine bases?  

• 1) GATCAATGC  
• 2) GCUAGACAA  
• 3) TGCCTAACG  
• 4) UAGCGGUAA  

Solution

Adenine and guanine are purine bases.     Thymine, cytosine and uracil are pyrimidine bases.     In option A - GATCAATGC - two thymine molecules and two cytosine molecules are present.  

Q49. DNA is composed of repeating units of

• 1) Ribonucleotides
• 2) Ribonucleosides
• 3) Deoxyribonucleotides
• 4) Deoxyribonucleosides

Solution

A nucleotide is composed of a nitrogen base, pentose sugar (deoxyribose in DNA) and phosphate. Thus, DNA is said to be composed of repeating units of deoxyribonucleotides.

Q50. Name any two inorganic constituents found in the living tissue.

Solution

Magnesium and calcium carbonate

Q51. Represent the glycogen molecule diagrammatically. What are the two ends of a polysaccharide chain called?

Solution

The left end of a polysaccharide chain is called the non-reducing end and the right end is called the reducing end.  

Q52. Give an example of anabolic pathway.  

Solution

Example of the anabolic pathway: Formation of cholesterol from acetic acid  

Q53. What are phospholipids?

Solution

Lipids which consist of phosphorus and phosphorylated organic compounds are called phospholipids.

Q54. What is the rate of a chemical or physical process? When is the rate also called velocity?

Solution

The rate of chemical or physical process is the amount of product formed per unit time. When the direction is specified, the rate is also called velocity.

Q55. Feedback inhibition of enzymes is affected by which of the following:

• 1) Substrate
• 2) End-products
• 3) Intermediate and products
• 4) Enzyme

Solution

Feedback inhibition is a mechanism when the end-product of a chemical reaction results in blocking the enzyme activity of the key enzyme which resulted in its production. When the concentration of the end-product rises, it binds to the enzyme at a site different from the active site and changes the structure of the enzyme. As a result, the substrate can no longer bind to the enzyme and the reaction stops.

Q56. Define living state.

Solution

The living state is a non-equilibrium steady state to be able to perform work.

Q57. What is a nucleotide?

Solution

A nucleotide is the combination of a nitrogenous base, a pentose sugar and a phosphate group esterified with the pentose sugar.

Q58. How is a peptide bond formed?

Solution

When the carboxyl (-COOH) group of one amino acid reacts with the (-NH2) group of the next amino acid, a molecule of water is eliminated by the process dehydration resulting in the formation of a peptide bond.

Q59. The two strands of DNA are held together by bonds of

• 1) Carbon
• 2) Hydrogen
• 3) Nitrogen
• 4) Oxygen

Solution

Two hydrogen bonds present between adenine and thymine and three hydrogen bonds present between cytosine and guanine hold the two strands of DNA together.

Q60. Which enzyme converts glucose into alcohol?

• 1) Diastase
• 2) Invertase
• 3) Lipase
• 4) Zymase

Solution

Zymase is an enzyme complex generally formed in yeast. It catalyses the conversion of glucose to form ethanol and carbon dioxide. This conversion is called fermentation.

Q61. The enzyme which cuts DNA is

• 1) DNA ligase
• 2) Restriction endonucleases
• 3) DNA lyase
• 4) DNA polymerase

Solution

Restriction endonucleases are a group of enzymes which bring about cuts in DNA at specific sequences. They are also called biological scissors.

Q62. The amino acid essential in man is

• 1) Serine
• 2) Phenylalanine
• 3) Aspartic acid
• 4) Creatinine

Solution

Phenylalanine is an essential amino acid in man. It must be ingested with food as it is important for survival and is not synthesised in the human body.

Q63. The number of base pairs present in one turn of DNA is  

• 1) 11  
• 2) 10  
• 3) 9  
• 4) 12  

Solution

One turn of DNA double helix is 3.4 nm long.     Each turn contains 10 base pairs.     Thus, the distance between two base pairs in DNA is 0.34 nm.  

Q64. Which one is true for ATP?  

• 1) ATP is a prosthetic part of an enzyme.  
• 2) ATP is a coenzyme.  
• 3) ATP is an enzyme.  
• 4) ATP is organic ions of enzyme.  

Solution

ATP works in conjugation with many enzymes. It transfers the phosphate group to the substrate and releases energy.  

Q65. Lipids are part of the acid-insoluble fraction, but they are not strictly macromolecules. Justify.

Solution

Lipids are low molecular weight compounds. They are present in cell membranes and other membranes of the cell. While grinding the tissue with the trichloroacetic acid, the membranes are broken into pieces and form vesicles which are not water soluble. These vesicles of the membrane fragments get separated with the acid-insoluble pool and come with the macromolecular fraction. Hence, although lipids are part of the acid-insoluble fraction, they are not strictly macromolecules.

Q66. Differentiate between primary metabolites and secondary metabolites.

Solution

Primary Metabolites Secondary Metabolites Functions of primary metabolites in physiological processes are known. Functions of secondary metabolites in the human body are unclear. Examples: Amino acids, sugars Examples: Carotenoids, curcumin

Q67. ATP was discovered by

• 1) Bowman
• 2) Blackman
• 3) Lipmann
• 4) Karl Lohmann

Solution

Karl Lohmann discovered ATP in 1929. He discovered ATP in muscle cells. 

Q68. A homopolymer has only one type of building block called a monomer repeated 'n' number of times. A heteropolymer has more than one type of monomer. Proteins are heteropolymers made of amino acids. While a nucleic acid like DNA or RNA is made of only 4 types of nucleotide monomers, proteins are made of  

• 1) Only one type of monomer  
• 2) 40 types of monomers  
• 3) 3 types of monomers  
• 4) 20 types of monomers  

Solution

Amino acids joined by peptide bonds form proteins. Twenty types of amino acids are present in natural proteins.  

Q69. Give examples of the following: Acidic amino acid Basic amino acid Aromatic amino acid

Solution

Acidic amino acid - Glutamic acid Basic amino acid - Lysine Aromatic amino acid - Phenylalanine

Q70. An enzyme/protein is formed by chemically bonding together  

• 1) Lipases  
• 2) Amino acids  
• 3) Carbohydrates  
• 4) CO₂  

Solution

The amino group of one amino acid is joined to the carboxyl group of the other amino acid and forms peptide bonds. Thus, amino acids join by peptide bonds and result in the formation of proteins/enzymes.  

Q71. Name the following:     Polymer of fructose   Polymer of glucose   Polysaccharide containing I₂   A nucleic acid with pentose sugar  

Solution

Polymer of fructose - Inulin   Polymer of glucose - Cellulose   Polysaccharide containing I₂ - Starch   A nucleic acid with deoxyribose sugar - Deoxyribonucleic acid (DNA)  

Q72. Wilkin’s X-ray diffraction showed DNA diameter to be

• 1) 100   
• 2) 20   
• 3) 200 
• 4) 50 

Solution

Diameter of DNA molecule is 20     

Q73. Genetic engineering requires enzyme

• 1) Lipase
• 2) DNase
• 3) Restriction endonuclease
• 4) Amylase

Solution

Restriction endonucleases are known as biological scissors. They are of different types. Each restriction endonuclease cuts the DNA at a specific site only, resulting in the formation of a fragment which can be used for recombination techniques.

Q74. One mole of glucose on metabolism liberates how many kilocalories of energy?

• 1) 160
• 2) 280
• 3) 80
• 4) 180

Solution

On metabolism, glucose produces carbon dioxide, water and some nitrogenous compounds along with the release of energy which can be used by the cells. One mole of glucose on oxidation releases 280 kilocalories of energy.

Q75. End-products of the same metabolic pathway can be different in different conditions. Justify.

Solution

The end-products of the same metabolic pathway can be different in different conditions. Example: If glycolysis occurs in aerobic conditions, the end-product is pyruvic acid. If glycolysis occurs in anaerobic conditions, the end-product is lactic acid. In yeasts, during fermentation, the same process leads to the formation of ethanol.

Q76. Protein synthesis in an animal cell takes place  

• 1) In the cytoplasm as well as in the mitochondria
• 2) Only in the cytoplasm
• 3) Only on ribosomes attached to the nuclear envelope
• 4) In the nucleolus as well as in the cytoplasm

Solution

Protein synthesis takes place on ribosomes which are found in the cytoplasm and mitochondria. 

Q77. Explain the effect of the concentration of substrate on the activity of enzyme.  

Solution

With an increase in the substrate concentration, the velocity of the enzyme reaction increases.     At some point, the number of enzyme molecules is lower than the number of substrate molecules.     The reaction reaches a point of saturation where there no free enzyme molecules to bind with the substrate.     Hence, the rate velocity or the rate of the reaction at the saturation state is maximum, which is V_max.        

Q78. Write one characteristic feature of prosthetic cofactors.

Solution

Prosthetic groups bind tightly with the apoenzyme.

Q79. Which of the following are the most diverse molecules of a cell?

• 1) Proteins
• 2) Carbohydrates
• 3) Lipids
• 4) Mineral salts

Solution

Proteins are the most diverse molecules of a cell. They can have a primary, secondary, tertiary or quaternary structure. Amino acids are the building blocks of proteins, and 20 different amino acids occur in natural proteins.

Q80. What are unsaturated fatty acids?

Solution

Fatty acids with one or more C = C double bonds are called unsaturated fatty acids.

Q81. The combination of apoenzyme and coenzyme produces  

• 1) Enzyme-substrate complex  
• 2) Enzyme-product complex  
• 3) Prosthetic group  
• 4) Holoenzyme  

Solution

The apoenzyme is the protein part of a conjugated enzyme, and the coenzyme is the non-protein part.     The combination of the apoenzyme and the coenzyme results in the formation of a functional enzyme which is called holoenzyme.  

Q82. The protein part of a conjugated enzyme is  

• 1) Holoenzyme  
• 2) Apoenzyme  
• 3) Coenzyme  
• 4) Isoenzyme  

Solution

A functional conjugated enzyme contains one protein part and the other cofactor or prosthetic group.     The protein part is called apoenzyme.  

Q83. Enzymes, vitamins and hormones are common in  

• 1) Regulating metabolism  
• 2) Being proteinaceous  
• 3) Enhancing oxidative metabolism  
• 4) Being synthesised in the body of organisms  

Solution

Enzymes, vitamins and hormones, all help in regulating different metabolic processes in the body.  

Q84. What are α-amino acids?

Solution

Amino acids in which the amino group and the acidic group are present as the substituents on the same α-carbon are called α-amino acids.

Q85. Write the expression used for the rate of physical or chemical process.  

Solution

The rate of physical or chemical process =  

Q86. Name the bond which links monosaccharides to form a polysaccharide.

Solution

The glycosidic bond joins monosaccharides to form a polysaccharide.

Q87. Write the name of the chemical used during the chemical analysis of liver tissue.

Solution

Trichloroacetic acid is used for the chemical analysis of liver tissue.

Q88. What is the unit used to measure the concentration of hormones present in living organisms?

Solution

The unit used to measure the concentration of hormones present in living organisms is nanogram/ml.

Q89. A peptide bond is formed between which amino acids?  

• 1) 2 and 3  
• 2) 1 and 2  
• 3) 2 and 4  
• 4) 1 and 3  

Solution

A peptide bond is formed between the amino group of the first and the carboxyl group of the second amino acid.  

Q90. Cholesterol is

• 1) Protein
• 2) Wax
• 3) Monosaccharide
• 4) Sterol

Solution

Cholesterol is a sterol. It is a steroid present in abundance in animal tissues. Its formula is C₂₇H₄₅OH.

Q91. Name two alkaloids and flavonoids.

Solution

Alkaloids: Morphine, codeine Flavonoids: Quercetin, apigenin

Q92. Define optimum temperature.

Solution

The temperature at which an enzyme shows its highest activity is called optimum temperature.

Q93. Define inhibitor.

Solution

An inhibitor is a substance which shuts off the activity of the enzyme by binding to the active site or some other site.

Q94. Name any two nucleotides.

Solution

Guanylic acid Cytidylic acid

Q95. State the factors affecting the activity of enzymes.

Solution

Factors affecting the activity of enzymes are as follows: Temperature pH Change in substrate concentration

Q96. The most abundant mineral of the animal body is

• 1) Potassium
• 2) Calcium
• 3) Iron
• 4) Sodium

Solution

Calcium is the most abundant mineral of an animal body. It contributes to about 2.5% of the total elements present in a cell.

Q97. Define biomolecules.

Solution

All the carbon compounds which are obtained from living tissues are called biomolecules.

Q98. There cannot be a living state without metabolism. Justify. OR The living state and metabolism are synonymous. Justify.

Solution

The living state is non-equilibrium steady state able to perform work. Metabolism provides the mechanism for energy. The living process is a constant effort to prevent falling into equilibrium.

Q99. Define cofactors.

Solution

Cofactors are the non-protein constituents which bind to the enzyme to make the enzyme catalytically active.

Q100. Name the vitamin present in NADP.

Solution

Niacin is present in NADP.

Q101. One turn of the DNA double helix spans a distance of

• 1) 2.46 nm
• 2) 4.26 nm
• 3) 4.56 nm
• 4) 3.4 nm

Solution

One turn of DNA double helix is 3.4 nm long.

Q102. What are proteins?

Solution

Proteins are polypeptides, i.e. macromolecules formed of a linear chain of amino acids linked to each other by peptide bonds.

Q103. Nucleotide, found free in the cells, is

• 1) ATP
• 2) ADP
• 3) AMP
• 4) cAMP

Solution

A triphosphate form of a nucleotide is the most stable form. ATP is a nucleotide which can be found free, unincorporated in the cell.

Q104. Describe the salient features of B-DNA.  

Solution

Salient features of B-DNA are as follows:  The two strands of polynucleotides run anti-parallel.  The backbone of the double helical structure is formed by the sugar-phosphate-sugar chain.  The nitrogenous bases lie perpendicular to the backbone of the molecule. They lie on the inner side.  There is a complementary base pairing between two anti-parallel strands. Example: A pairs with T and G pairs with C.  A and T are paired by the formation of two hydrogen bonds, and G and C are paired by the formation of three hydrogen bonds.  Each strand of DNA appears like a helical staircase.  Each step of the strand is represented by a pair of bases.  At each step, the strand turns 36°.  One full turn of the strand involves 10 base pairs.  The distance between two successive sugar molecules is 3.4.  

Q105. Describe the formation of a phosphodiester bond in a nucleic acid.

Solution

A phosphate bond links the 3′ carbon of one sugar of one nucleotide with the hydroxyl group of the 5′ carbon of the sugar of the succeeding nucleotide. This results in the formation of an ester bond. Because such an ester bond is formed on either side of the nucleotide, it is called a phosphodiester bond.

Q106. Define optimum pH.

Solution

The pH at which an enzyme shows its highest activity is called its optimum pH.

Q107. Describe the chemical analysis carried out for a plant tissue.  

Solution

The tissue to be analysed is ground with trichloroacetic acid.     The thick slurry of tissue and trichloroacetic acid is then strained through cheesecloth.     Two solutions are obtained - filtrate and retentate.     The filtrate is an acid-soluble pool which contains a number of organic compounds.     Retentate is the acid-insoluble fraction of the slurry.  

Q108. Write the three types of cofactors.

Solution

Three types of cofactors are Prosthetic groups Coenzymes Metal ions

Q109. Draw the structures of Adenosine Adenylic acid

Solution

Structure of Adenosine:   Structure of Adenylic Acid:  

Q110. A unit composed of sugar and nitrogen base linked by a glycosidic bond is  

• 1) Nucleotide  
• 2) Glycoside  
• 3) Purine  
• 4) Nucleoside  

Solution

A nucleoside contains a pentose sugar and a nitrogen base joined by glycosidic bonds.     A purine is an aromatic double ring compound. It contains a pyrimidine ring and an imidazole ring fused together.     A glycoside is a compound which contains a sugar molecule bound to a functional group through glycosidic bonds.     A nucleotide contains a pentose sugar, a nitrogen base and a phosphate molecule.  

Q111. When is a protein structure called a tertiary structure?  

Solution

When the long protein chain gets folded upon itself like a hollow woollen ball, the structure is called the tertiary structure of a protein.  

Q112. Expand the term RuBisCO.

Solution

RuBisCO - Ribulose bisphosphate carboxylase-oxygenase

Q113. What is enzyme inhibition?

Solution

Enzyme inhibition is the process during which an inhibitor binds to the enzyme either on its active site or some other site and shuts off the activity of the enzyme.

Q114. Write the IUPAC name of glycerol.

Solution

The IUPAC name of glycerol is trihydroxy propane.

Q115. Name any two nucleosides.

Solution

Uridine Thymidine

Q116. Describe the catalytic cycle of enzyme action. Also write the symbolic equation of the formation of the enzyme-product complex.  

Solution

The catalytic cycle of an enzyme action occurs in the following steps:     The substrate binds to the active site of the enzyme.   The binding of the substrate induces a change in the shape of the enzyme molecule, and the substrate firms itself more tightly into the active site.   The active site results in the breaking of the chemical bonds of the substrate, resulting in the formation of a new enzyme-product complex.   The enzyme molecule releases the product of the reaction and becomes free again to receive the new substrate molecule.      

Q117. Which parts of the cells form an acid-insoluble fraction?

Solution

Cytoplasm and cell organelles form the acid-insoluble fraction.

Q118. State any one property of amino acids.

Solution

-NH₂ and -COOH groups of amino acids exhibit the ionisable nature.

Q119. Give any two examples of aromatic amino acids.

Solution

Examples of aromatic amino acids are tryptophan and tyrosine.

Q120. Write the symbolic representation for ligases.  

Solution

Symbolic representation for ligases:    

Q121. Name the protein which is most abundantly found in the biosphere.

Solution

Ribulose bisphosphate carboxylase-oxygenase (RuBisCO) is the most abundantly found in the biosphere.

Q122. What is the energy currency in living organisms?

Solution

Adenosine triphosphate (ATP) is the energy currency in living organisms.

Q123. Draw a primary structure of a hypothetical protein.

Solution

Primary Structure of a Hypothetical Protein:  

Q124. Explain the graph representing the concept of activation energy.

Solution

  In the above graph, the y-axis represents the potential energy content. The x-axis represents the progression of structural transformation. The difference in the activation energy of substrate and product is indicated on the graph. If P is at a lower level than S, then the reaction is an exothermic reaction. The difference in average energy content of S from that of its transition state is called activation energy.

Q125. Write the percent weight of the following in the human body. Oxygen Nitrogen Sodium Carbon

Solution

Oxygen - 65% Nitrogen - 3.3% Sodium - 0.2% Carbon - 18.5%

Q126. In solutions of different pH, the structure of amino acids changes. Justify.  

Solution

The -NH₂ and -COOH groups of amino acids exhibit an ionisable nature. With a change in pH, these groups undergo ionisation. Hence, the structure of amino acid changes in solutions of different pH.   

Q127. Explain how metal ions activate enzyme action. Give one example.  

Solution

Metal ions form coordinate bonds with the side chains at the active site. At the same time, they form one or more coordinate bonds with the substrate. Example: Zinc acts as a cofactor for the proteolytic enzyme carboxypeptidase.  

Q128. Name the following: Store house of energy in plants. Molecules present in the helical portion of a starch molecule. A polysaccharide present in the exoskeleton of arthropods. Heterocyclic compound present in nucleic acids.

Solution

Store house of energy in plants - Starch Molecules present in the helical portion of a starch molecule - I₂ A polysaccharide present in the exoskeleton of arthropods - Chitin Heterocyclic compounds present in nucleic acids - Nitrogenous bases

Q129. What are ribozymes?

Solution

Nucleic acids which act like enzymes are called ribozymes.

Q130. Give examples of any two commercial products which are cellulosic.

Solution

Two commercial cellulosic products are paper pulp and cotton fibre.

Q131. Distinguish between anabolic pathway and catabolic pathway.  

Solution

Anabolic Pathway     Catabolic Pathway     Chemical reactions in which the formation of complex structures from simpler structures occurs are anabolic pathways.   Chemical reactions in which the complex molecules are degraded into simple molecules are called catabolic pathways.   These pathways consume energy.   These pathways release energy.   Example: Formation of protein from amino acid   Example: Conversion of glucose into lactic acid  

Q132. Give an example of a lectin.

Solution

Conconavalin A is a lectin (carbohydrate-binding protein) which is extracted from the jack-bean

Q133. Explain the mechanism of enzyme inhibition.

Solution

An inhibitor usually closely resembles the substrate in its molecular structure. Due to structural resemblance, the inhibitor competes with the substrate for the substrate-binding site of the enzyme. Hence, the substrate cannot bind to the enzyme which results in a decline of enzyme action.

Q134. Name the following: 20 carbon atom fatty acid 16 carbon atom fatty acid

Solution

20 carbon atom fatty acid - Arachidonic acid 16 carbon atom fatty acid - Palmitic acid

Q135. Write the names of two complex polysaccharides consisting of amino sugars.

Solution

The two complex polysaccharides consisting of amino sugars are glucosamine and N-acetyl galactosamine.

Q136. Name the four inorganic compounds present in the acid-insoluble fraction of the slurry of living tissue and trichloroacetic acid.

Solution

Proteins, nucleic acids, polysaccharides and lipids are present in the acid-insoluble fraction of the slurry of living tissue and trichloroacetic acid.

Q137. Draw the structures of     Cholesterol   Uracil   Triglyceride  

Solution

Cholesterol:         Uracil:         Triglyceride:      

Q138. Name the nucleic acid which consists of a monosaccharide pentose sugar.

Solution

Ribonucleic acid (RNA)

Q139. Define metabolic pathways.  

Solution

Metabolic pathways are a series of linked reactions through which biomolecules are converted into each other.  

Q140. What is the active site of an enzyme?

Solution

An active site is a crevice on the enzyme molecule into which a substrate molecule fits.

Q141. Write the zwitterionic form of amino acids.  

Solution

Zwitterionic form of amino acids:      

Q142. Define activation energy.

Solution

The difference in average energy content of a substrate from its transition state is called activation energy.

Q143. Describe the primary structure of protein.  

Solution

The primary structure of protein gives the positional information or the information about the sequence of amino acids.     The left end of the protein chain is represented by the first amino acid (i.e. the N-terminal amino acid) and the right end is represented by the last amino acid (i.e. the C-terminal amino acid).  

Q144. How many amino acids exist in the biosphere?

Solution

20 amino acids exist in the biosphere.

Q145. Which of the following enzymes is used in making a detergent?

• 1) Amylase
• 2) Cellulase
• 3) Protease
• 4) Peptidase

Solution

Protease helps to remove tough stains caused by protein substances. Hence, they are widely used enzymes in detergents.

Q146. Name the bond which links amino acids in a polypeptide.

Solution

The peptide bond links amino acids in a polypeptide.

Q147. Identify the following:     Protein which enables glucose to transport into cells   Intercellular ground substance  

Solution

Protein which enables glucose to transport into cells - GLUT-4   Intercellular ground substance - Collagen  

Q148. Describe any five classes of enzymes.  

Solution

There are a total of six classes into which enzymes are categorised:     Transferases: These enzymes catalyse the transfer of a group (G) between a pair of substrates (S and S′).         Dehydrogenases (Oxidoreductases): These enzymes catalyse oxidoreduction between two substrates.         Hydrolases: These enzymes catalyse the hydrolysis of ester, ether, peptide, glycosidic linkages, C-C, C-halide and P-N bonds.   Ligases: They catalyse the linking together of two compounds. These enzymes join C-°, C-S, C-N and P-° bonds.   Isomerases: These enzymes catalyse the interconversion of optical, geometric or positional isomers.  

Q149. State the functions of proteins.

Solution

Functions of proteins: Transport nutrients across the cell membrane. Example: GLUT-4 Fight against infectious agents. Example: Antibodies Work as enzyme. Example: Trypsin Act as hormones. Example: Insulin

Q150. What are saturated fatty acids?

Solution

Fatty acids which do not contain any C = C double bond are called saturated fatty acids.

Q151. State the number of hydrogen bonds present between the following base pairs:     Adenine and Thymine   Guanine and Cytosine  

Solution

Two hydrogen bonds - Adenine and Thymine   Three hydrogen bonds - Guanine and Cytosine  

Q152. Give any two examples of amino acids.

Solution

Two examples of amino acids are proline and alanine.