Match the entries in Group I with that in Group IIGroup IGroup IIP) Fehling's test1) α-Amino acidQ) Ninhydrin reaction2) Reducing sugarR) Biuret reaction3) Sulfhydryl groupS) Nitroprusside reaction4) Peptide linkage

The correct match is P-2, Q-1, R-4, S-3.Fehling's test detects reducing sugars, which reduce Cu2+ to red Cu2O.Ninhydrin reacts with the free amino group of α-amino acids to give a purple colour.The biuret reaction detects peptide linkages, giving a violet colour with Cu2+ in alkali.The nitroprusside reaction detects free sulfhydryl (-SH) groups, as in cysteine.The option P-4, Q-1, R-2, S-3 gets ninhydrin and nitroprusside right but swaps Fehling's and biuret. The other two misplace ninhydrin as well.

If cells of Escherichia coli are grown in a medium containing radioactive 32P, the 32P would be found in all, except :

The 32P would not be found in carbohydrates.DNA and RNA contain phosphate in every nucleotide of their sugar-phosphate backbone, and ATP carries three phosphate groups, so all three take up labelled phosphorus. This is why Hershey and Chase used 32P to label phage DNA.Carbohydrates as such are made of carbon, hydrogen and oxygen only. Phosphorylated sugars occur as metabolic intermediates, but the carbohydrates of the cell, such as glycogen and the polysaccharides, contain no phosphorus, so they are the exception.

Biomolecules Overview Questions and Answers

Q: Out of the following options, heparin can be classified as a/an:

Heparin is an anticoagulant.Heparin, a sulphated polysaccharide found in mast cells, prevents blood clotting by strongly activating antithrombin, which inactivates thrombin and factor Xa. It is used to keep blood samples from clotting and to prevent and treat thrombosis.Hyaluronic acid is a different polysaccharide found in joint fluid and connective tissue, which acts as a lubricant; heparin is neither. A mucoprotein is a protein-carbohydrate complex of mucus, which heparin is not.

Q: If an aqueous solution has a hydrogen ion concentration of \(10^{-3}\) M, what is the concentration of hydroxyl ion ?

The hydroxyl ion concentration is \(10^{-11}\) M.In water at 25°C the ionic product is constant:\[ \begin{aligned} [\mathrm{H^{+}}][\mathrm{OH^{-}}] &= 10^{-14} \\ [\mathrm{OH^{-}}] &= \frac{10^{-14}}{10^{-3}} = 10^{-11}\ \text{M} \end{aligned} \]Equivalently, pH 3 means pOH \(14 - 3 = 11\). \(10^{-14}\) M is the ionic product itself, not a concentration; \(10^{-10}\) and \(10^{-12}\) M come from subtracting the exponents wrongly by one.

Q: Hydrogen bond can be formed between the pair of atoms such as :

The pair is hydrogen and nitrogen.A hydrogen bond forms between a hydrogen atom covalently bonded to an electronegative atom and a lone pair on another strongly electronegative atom, in biology almost always nitrogen or oxygen. So the bond itself links a hydrogen and an acceptor such as nitrogen, as in the N-H...N and N-H...O bonds of DNA base pairs.Carbon is not electronegative enough to act as a normal acceptor, so the carbon pairs are wrong. Oxygen and nitrogen are both electronegative, but they are the donor and acceptor atoms; a hydrogen bond cannot form between them unless a hydrogen sits between them.

Q: Maleic acid and Fumaric acid are :

Maleic acid and fumaric acid are geometric isomers.Both are butenedioic acid, HOOC-CH=CH-COOH. Rotation about the C=C double bond is restricted, so the two carboxyl groups can sit on the same side (maleic acid, the cis form) or on opposite sides (fumaric acid, the trans form). They differ in properties: maleic acid melts far lower and readily forms an anhydride because its carboxyl groups are close together.Neither molecule has a chiral centre, so they are not chiral isomers or enantiomers (mirror-image pairs). Cis-trans isomers are, strictly, one kind of diastereomer (stereoisomers that are not mirror images), but the specific term for this pair, and the one the key expects, is geometric isomers.

Q: Carbon-14 undergoes beta decay upon which it is converted into a new element having :

The new element has an increased atomic number.In beta (minus) decay a neutron in the nucleus changes into a proton, emitting an electron and an antineutrino. The number of protons rises by one while the total number of nucleons stays the same:\[ \begin{aligned} ^{14}_{6}\text{C} &\rightarrow\ ^{14}_{7}\text{N} \\ &+ e^{-} + \bar{\nu} \end{aligned} \]So carbon-14 becomes nitrogen-14, and the mass number is unchanged at 14. A decreased atomic number would result from positron emission or electron capture, and a change of mass number needs alpha decay (a fall of 4), which beta decay never causes.

Q: Liquid scintillation counting is used for measurement of radioactivity of :

Liquid scintillation counting is used for \(^{14}\text{C}\).Carbon-14 (like tritium and sulphur-35) emits only weak beta particles, which travel a fraction of a millimetre in a sample and are absorbed before they could reach an external detector. In liquid scintillation counting the sample is dissolved in a cocktail containing a fluor, so every beta particle excites the solvent close to where it is emitted. The flashes of light are counted by photomultiplier tubes.Iodine-131 and the chromium isotopes used as labels emit penetrating gamma rays and are measured in a gamma counter with a sodium iodide crystal. Uranium-235 is an alpha emitter used as nuclear fuel, not as a biological tracer.

Q: Electromagnetic radiation consists of discrete packets of energy which are called as :

The discrete packets of energy are called photons.Planck proposed that radiation is emitted in quanta, and Einstein's explanation of the photoelectric effect (1905) showed that light itself consists of particles of energy \(E = h\nu\), where h is Planck's constant and \(\nu\) the frequency. These quanta of electromagnetic radiation are photons; they have no rest mass and travel at the speed of light.Quarks are the particles that make up protons and neutrons. Electrons are charged particles of matter, and positrons are their antiparticles. None of them is a packet of electromagnetic radiation.

Q: By what process does Thorium-230 decay to radium-226 ?

Thorium-230 decays to radium-226 by alpha emission.The mass number falls by 4 (230 to 226) and the atomic number by 2 (thorium 90 to radium 88). An alpha particle is a helium-4 nucleus, two protons and two neutrons, so alpha emission is the only one of these processes that changes the mass number at all.Gamma emission changes neither number. Beta emission and electron capture change the atomic number by one while leaving the mass number at 230.

Match the entries in Group I with that in Group II

Group I	Group II
P) Fehling's test	1) α-Amino acid
Q) Ninhydrin reaction	2) Reducing sugar
R) Biuret reaction	3) Sulfhydryl group
S) Nitroprusside reaction	4) Peptide linkage

A.P-1, Q-2, R-3, S-4
B.P-3, Q-4, R-1, S-2
C.P-2, Q-1, R-4, S-3
D.P-4, Q-1, R-2, S-3

Exam Year(s)

IIT JAM - 2018,

Answer: C

The correct match is P-2, Q-1, R-4, S-3.

Fehling's test detects reducing sugars, which reduce Cu²⁺ to red Cu₂O.
Ninhydrin reacts with the free amino group of α-amino acids to give a purple colour.
The biuret reaction detects peptide linkages, giving a violet colour with Cu²⁺ in alkali.
The nitroprusside reaction detects free sulfhydryl (-SH) groups, as in cysteine.

The option P-4, Q-1, R-2, S-3 gets ninhydrin and nitroprusside right but swaps Fehling's and biuret. The other two misplace ninhydrin as well.

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Out of the following options, heparin can be classified as a/an:

A.Anticoagulant
B.Hyaluronic acid
C.Lubricant
D.Mucoprotein

Exam Year(s)

RSMSSB Livestock Assistant - 2025, RSMSSB - 2025,

Answer: A

Heparin is an anticoagulant.

Heparin, a sulphated polysaccharide found in mast cells, prevents blood clotting by strongly activating antithrombin, which inactivates thrombin and factor Xa. It is used to keep blood samples from clotting and to prevent and treat thrombosis.

Hyaluronic acid is a different polysaccharide found in joint fluid and connective tissue, which acts as a lubricant; heparin is neither. A mucoprotein is a protein-carbohydrate complex of mucus, which heparin is not.

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If an aqueous solution has a hydrogen ion concentration of \(10^{-3}\) M, what is the concentration of hydroxyl ion ?

A.\(10^{-14}\) M
B.\(10^{-10}\) M
C.\(10^{-11}\) M
D.\(10^{-12}\) M

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

The hydroxyl ion concentration is \(10^{-11}\) M.

In water at 25°C the ionic product is constant:

\[ \begin{aligned} [\mathrm{H^{+}}][\mathrm{OH^{-}}] &= 10^{-14} \\ [\mathrm{OH^{-}}] &= \frac{10^{-14}}{10^{-3}} = 10^{-11}\ \text{M} \end{aligned} \]

Equivalently, pH 3 means pOH \(14 - 3 = 11\). \(10^{-14}\) M is the ionic product itself, not a concentration; \(10^{-10}\) and \(10^{-12}\) M come from subtracting the exponents wrongly by one.

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Hydrogen bond can be formed between the pair of atoms such as :

A.Hydrogen and Carbon
B.Hydrogen and Nitrogen
C.Oxygen and Nitrogen
D.Oxygen and Carbon

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The pair is hydrogen and nitrogen.

A hydrogen bond forms between a hydrogen atom covalently bonded to an electronegative atom and a lone pair on another strongly electronegative atom, in biology almost always nitrogen or oxygen. So the bond itself links a hydrogen and an acceptor such as nitrogen, as in the N-H...N and N-H...O bonds of DNA base pairs.

Carbon is not electronegative enough to act as a normal acceptor, so the carbon pairs are wrong. Oxygen and nitrogen are both electronegative, but they are the donor and acceptor atoms; a hydrogen bond cannot form between them unless a hydrogen sits between them.

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Maleic acid and Fumaric acid are :

A.Geometric isomers
B.Chiral isomers
C.Enantiomers
D.Diastereomers

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

Maleic acid and fumaric acid are geometric isomers.

Both are butenedioic acid, HOOC-CH=CH-COOH. Rotation about the C=C double bond is restricted, so the two carboxyl groups can sit on the same side (maleic acid, the cis form) or on opposite sides (fumaric acid, the trans form). They differ in properties: maleic acid melts far lower and readily forms an anhydride because its carboxyl groups are close together.

Neither molecule has a chiral centre, so they are not chiral isomers or enantiomers (mirror-image pairs). Cis-trans isomers are, strictly, one kind of diastereomer (stereoisomers that are not mirror images), but the specific term for this pair, and the one the key expects, is geometric isomers.

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Carbon-14 undergoes beta decay upon which it is converted into a new element having :

A.Increased atomic number
B.Decreased atomic number
C.Increased mass number
D.Decreased mass number

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

The new element has an increased atomic number.

In beta (minus) decay a neutron in the nucleus changes into a proton, emitting an electron and an antineutrino. The number of protons rises by one while the total number of nucleons stays the same:

\[ \begin{aligned} ^{14}_{6}\text{C} &\rightarrow\ ^{14}_{7}\text{N} \\ &+ e^{-} + \bar{\nu} \end{aligned} \]

So carbon-14 becomes nitrogen-14, and the mass number is unchanged at 14. A decreased atomic number would result from positron emission or electron capture, and a change of mass number needs alpha decay (a fall of 4), which beta decay never causes.

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Liquid scintillation counting is used for measurement of radioactivity of :

A.\(^{14}\text{C}\)
B.\(^{131}\text{I}\)
C.\(^{57}\text{Cr}\)
D.\(^{235}\text{U}\)

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

Liquid scintillation counting is used for \(^{14}\text{C}\).

Carbon-14 (like tritium and sulphur-35) emits only weak beta particles, which travel a fraction of a millimetre in a sample and are absorbed before they could reach an external detector. In liquid scintillation counting the sample is dissolved in a cocktail containing a fluor, so every beta particle excites the solvent close to where it is emitted. The flashes of light are counted by photomultiplier tubes.

Iodine-131 and the chromium isotopes used as labels emit penetrating gamma rays and are measured in a gamma counter with a sodium iodide crystal. Uranium-235 is an alpha emitter used as nuclear fuel, not as a biological tracer.

Discuss in Forum

Electromagnetic radiation consists of discrete packets of energy which are called as :

A.Quarks
B.Photons
C.Positrons
D.Electrons

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The discrete packets of energy are called photons.

Planck proposed that radiation is emitted in quanta, and Einstein's explanation of the photoelectric effect (1905) showed that light itself consists of particles of energy \(E = h\nu\), where h is Planck's constant and \(\nu\) the frequency. These quanta of electromagnetic radiation are photons; they have no rest mass and travel at the speed of light.

Quarks are the particles that make up protons and neutrons. Electrons are charged particles of matter, and positrons are their antiparticles. None of them is a packet of electromagnetic radiation.

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By what process does Thorium-230 decay to radium-226 ?

A.Gamma emission
B.Alpha emission
C.Beta emission
D.Electron capture

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: B

Thorium-230 decays to radium-226 by alpha emission.

The mass number falls by 4 (230 to 226) and the atomic number by 2 (thorium 90 to radium 88). An alpha particle is a helium-4 nucleus, two protons and two neutrons, so alpha emission is the only one of these processes that changes the mass number at all.

Gamma emission changes neither number. Beta emission and electron capture change the atomic number by one while leaving the mass number at 230.

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10.

If cells of Escherichia coli are grown in a medium containing radioactive ³²P, the ³²P would be found in all, except :

A.DNA
B.RNA
C.ATP
D.Carbohydrates

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: D

The ³²P would not be found in carbohydrates.

DNA and RNA contain phosphate in every nucleotide of their sugar-phosphate backbone, and ATP carries three phosphate groups, so all three take up labelled phosphorus. This is why Hershey and Chase used ³²P to label phage DNA.

Carbohydrates as such are made of carbon, hydrogen and oxygen only. Phosphorylated sugars occur as metabolic intermediates, but the carbohydrates of the cell, such as glycogen and the polysaccharides, contain no phosphorus, so they are the exception.

Discuss in Forum

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