Biomolecules — Page 12 | NEET Chemistry

Q111

Which one of the following statements is not true about enzymes?

A Enzymes are non-specific for a reaction and substrate.

B Almost all enzymes are proteins.

C Enzymes work as catalysts by lowering the activation energy of a biochemical reaction.

D The action of enzymes is temperature and pH specific.

Correct Answer

Option A

Solution

Enzymes are mostly proteins.

They function as catalysts in biochemical reactions by lowering the energy of activation.

They are highly specific w.r.t. temperature and pH in their action.

Q112

Given below are two statements: Statement I: D-(+)-glucose + D-(+) fructose

\xrightarrow{-\mathrm{H}_2 \mathrm{O}}

Sucrose

\text{ sucrose } \xrightarrow{\text{ hydrolysis }} \mathrm{D}-(+) \text{ glucose }+\mathrm{D}-(+) \text{ fructose }

Statement II: Invert sugar is formed during sucrose hydrolysis In the light of the above statements, choose the correct answer from the options given below

A Both Statement I and Statement II are False

B Statement I is false but Statement II are true

C Both Statement I and Statement II are true

D Statement I is true but Statement II is false

Correct Answer

Option B

Solution

In Statement I, the reaction shown is incorrect.

During the hydrolysis of sucrose, D-(+)-glucose and D-(-)-fructose are produced.

However, the statement incorrectly specifies D-(+)-fructose, making Statement I inaccurate.

Statement II is accurate.

When sucrose undergoes hydrolysis, it results in the formation of invert sugar, a mixture of glucose and fructose.

This change involves the inversion of optical rotation, which is where the term "invert sugar" comes from.

Q113

Match with $$

List - I		List - II
(B)	$\text{ Glucose } / \mathrm{HNO}_3$	(I)	Gluconic acid
(C)	$\text{ Glucose } / \mathrm{HI} / \Delta$	(II)	No reaction
(D)	Glucose/Bromine water	(III)	n-hexane
()		(IV)	Saccharic acid

A A-II, B-IV, C-III, D-I

B A-III, B-II, C-I, D-IV

C A-IV, B-I, C-III, D-II

D A-I, B-IV, C-III, D-II

Correct Answer

Option A

Solution

Glucose

\xrightarrow[\Delta]{\mathrm{NaHCO}_3}

no reaction Glucose

\xrightarrow[\Delta]{\mathrm{HNO}_3}

saccharic acid Glucose

\xrightarrow[\Delta]{\mathrm{HI}}

n-hexane Glucose

\xrightarrow[\Delta]{\mathrm{Br}_2}

Gluconic acid

Q114

If one strand of a DNA has the sequence ATGCTTCA, sequence of the bases in complementary strand is :

A CATTAGCT

B TACGAAGT

C ATGCGACT

D GTACTTAC

Correct Answer

Option B

Solution

DNA is made up of two strands that are complementary to each other.

The base pairing rules state that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).

Using these rules, we can determine the sequence of the complementary strand of the given DNA sequence ATGCTTCA.

Here's the pairing for the given sequence: A (adenine) pairs with T (thymine) T (thymine) pairs with A (adenine) G (guanine) pairs with C (cytosine) C (cytosine) pairs with G (guanine) T (thymine) pairs with A (adenine) T (thymine) pairs with A (adenine) C (cytosine) pairs with G (guanine) A (adenine) pairs with T (thymine) So, the complementary base sequence to the given DNA strand ATGCTTCA would be: 1.

A pairs with T 2.

T pairs with A 3.

G pairs with C 4.

C pairs with G 5.

T pairs with A 6.

T pairs with A 7.

C pairs with G 8.

A pairs with T Putting it all together, the complementary sequence is: TACGAAGT.

Therefore, the correct answer is: Option B - TACGAAGT

Q115

Deficiency of vitamin K causes :

A Cheilosis

B Decrease in blood clotting time

C Increase in blood clotting time

D Increase in fragility of RBC's

Correct Answer

Option C

Solution

Deficiency of vitamin K causes increase in blood clotting time.

Q116

The presence or absence of hydroxyl group on which carbon atom of sugar differentiates RNA and DNA ?

A 2nd

B 3rd

C 4th

D 1st

Correct Answer

Option A

Solution

RNA

has

D(-)

- Ribose and the

DNA

has

2

-Dexoy

D(-)

$-$ ribose as the carbohydrate unit. From the structures it is clear that

{2^{nd}}

carbon in

DNA

do not have

OH

group.

Q117

Identify the correct statements regarding enzymes

A Enzymes are specific biological catalysts that can normally function at very high temperature (T ~ 1000 K)

B Enzymes are specific biological catalysts that the posses well – defined active sites

C Enzymes are specific biological catalysts that can not be poisoned

D Enzymes are normally heterogeneous catalysts that are very specific in their action

Correct Answer

Option B

Solution

Enzymes are shape selective specific biological catalysts which normally functions effectively at body temperature.

Q118

Which of the following is not an example of fibrous protein?

A Keratin

B Albumin

C Collagen

D Myosin

Correct Answer

Option B

Solution

Fibrous proteins are characterized by their elongated, insoluble structure and often serve structural or mechanical roles.

Among the options provided, keratin, collagen, and myosin are examples of fibrous proteins.

Albumin, on the other hand, is a globular protein that is soluble in water.

It has a more spherical shape compared to the elongated shape of fibrous proteins.

Albumin is found in blood plasma and has various functions including maintaining osmotic pressure.

So, the correct answer is: Option B: Albumin.

Q119

Which of the following vitamin is helpful in delaying the blood clotting?

A Vitamin K

B Vitamin C

C Vitamin E

D Vitamin B

Correct Answer

Option A

Solution

Vitamin K is helpful in delaying the blood clotting.

Q120

Coagulation of egg, on heating is because of :

A Denaturation of protein occurs

B Biological property of protein remains unchanged

C Breaking of the peptide linkage in the primary structure of protein occurs

D The secondary structure of protein remains unchanged

Correct Answer

Option A

Solution

The coagulation of an egg on heating is because of Option A: Denaturation of protein occurs.

When an egg is heated, the proteins in the egg (primarily albumins) undergo denaturation.

This process involves the structural alteration of the protein molecules without breaking the peptide bonds that hold the amino acid sequences together.

Denaturation causes the proteins to unfold and then aggregate into a new, solid structure, which is what you observe as the egg white and yolk changing from liquid to solid.

This change is principally caused by the disruption of non-covalent bonds in the protein, such as hydrogen bonds, ionic bonds, and hydrophobic interactions.

Option B is incorrect because the biological property of the protein does indeed change during the process.

The protein in its denatured (coagulated) form does not function in the same way as it did in its native form.

Option C is also incorrect because the primary structure of the protein, defined by its amino acid sequence linked by peptide bonds, remains unaltered during denaturation.

The process does not involve the breaking of these peptide linkages.

Lastly, Option D is incorrect because the secondary structure of the protein, which includes α-helices and β-pleated sheets formed by hydrogen bonding, typically undergoes significant alteration during denaturation, contributing to the observable change in the egg's texture.