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NEET • CHEMISTRY • BIOMOLECULES

Biomolecules practice · Mixed difficulty

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Showing 1-30 of 191 questions

1 Easy

1 of 191

Remembering +4 | -1

A carbohydrate is treated with α-naphthol and conc.

{H_2}S{O_4}

. What colour will be formed at the junction of two liquids?

View answer and explanation

Correct option: B

Violet

The correct answer is B (Violet) because the Molisch's test, using α-naphthol and conc.

{H_2}S{O_4}

, produces a violet ring at the junction of the two liquids in the presence of carbohydrates.

2 Medium

2 of 191

Understanding +4 | -1

Drying oils are so called because they:

View answer and explanation

Correct option: D

Are highly unsaturated and so undergo atmospheric oxidation to yield resinous residue and becomes hard solid

Option D (Are highly unsaturated and so undergo atmospheric oxidation to yield resinous residue and becomes hard solid) is correct because drying oils contain many double bonds that react with oxygen, leading to polymerization and hardening.

3 Medium

3 of 191

Application +4 | -1

If specific rotation of glucose solution is

52^\circ

and that of fructose solution is

-92^\circ

then what will be the specific rotation of invert sugar?

View answer and explanation

Correct option: A

-20^\circ

Option A (-20°) is correct because the specific rotation of invert sugar is the average of glucose and fructose weighted by their concentrations, which are equal after hydrolysis.

4 Easy

4 of 191

Understanding +4 | -1

The compound, which give a positive ninhydrin test and a negative Benedict’s solution test, is

View answer and explanation

Correct option: D

A protein

Option D (A protein) is correct because proteins give a positive ninhydrin test and a negative Benedict’s solution test.

5 Medium

5 of 191

Remembering +4 | -1

A good example of an unsaturated acid got by the hydrolysis of an oil is:

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Correct option: C

Oleic acid

The correct answer is C (Oleic acid) because oleic acid is an unsaturated fatty acid commonly obtained from the hydrolysis of oils.

6 Hard

6 of 191

Understanding +4 | -1

Glycerine used as a preservative for fruits, vegetables due to

View answer and explanation

Correct option: C

Hygroscopic nature

Option C (Hygroscopic nature) is correct because glycerine's hygroscopic nature allows it to absorb moisture, reducing water activity and preventing microbial growth, thus preserving fruits and vegetables.

7 Hard

7 of 191

Remembering +4 | -1

The amino acid is directly used as the precursor in the formation of indole acetic acid.

View answer and explanation

Correct option: D

tryptophan

Option D (tryptophan) is correct because tryptophan is the direct precursor for the synthesis of indole acetic acid (IAA), a common auxin plant hormone.

8 Hard

8 of 191

Understanding +4 | -1

A chemist isolated a protein from crab and wanted to determine its molecular weight. Which of the following method would have given the best result for him?

View answer and explanation

Correct option: D

Osmotic pressure method

Option D (Osmotic pressure method) is correct because osmotic pressure is a colligative property that is particularly useful for determining the molecular weights of large molecules like proteins.

9 Medium

9 of 191

Understanding +4 | -1

Which statement about ribose is incorrect?

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Correct option: C

Has six carbon atoms

Option C (Has six carbon atoms) is correct because ribose is a pentose sugar, meaning it has five carbon atoms, not six.

10 Hard

10 of 191

Understanding +4 | -1

If one strand of DNA has the sequence ATCGTATG the sequence in the complementary strand would be:

View answer and explanation

Correct option: C

TAGCATAC

Option C (TAGCATAC) is correct because in DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Therefore, the complementary sequence is found by replacing each base with its pair.

11 Medium

11 of 191

Remembering +4 | -1

Which one is the complimentary base of adenine in one strand to that in the other strand of DNA?

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Correct option: D

Thymine

Option D (Thymine) is correct because, in DNA, adenine always pairs with thymine through two hydrogen bonds.

12 Medium

12 of 191

Analyzing +4 | -1

Assertion:- Sucrose and saccharin have nearly same sweetness index.

Reason:- Both compounds are the component of carbohydrate.

View answer and explanation

Correct option: D

If both assertion & reason are false

The correct answer is D (If both assertion & reason are false) because sucrose is much sweeter than saccharin, and saccharin is not a carbohydrate.

13 Medium

13 of 191

Remembering +4 | -1

Which of the following is a globular protein

View answer and explanation

Correct option: B

Insulin

Option B (Insulin) is correct because insulin is a globular protein, characterized by its spherical shape and solubility in water.

14 Easy

14 of 191

Understanding +4 | -1

The

\alpha

-amino acid which doesn’t give purple colour in the ninhydrin test is

View answer and explanation

Correct option: A

Proline

Option A (Proline) is correct because proline is a secondary amine, and its reaction with ninhydrin yields a yellow-orange color instead of the typical purple color.

15 Medium

15 of 191

Understanding +4 | -1

Secondary structure of proteins refers to:

View answer and explanation

Correct option: D

Regular folding patterns of continuous portion of the polypeptide chain

Option D (Regular folding patterns of continuous portion of the polypeptide chain) is correct because the secondary structure of proteins refers to local folding patterns like alpha-helices and beta-sheets.

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16 Medium

16 of 191

Remembering +4 | -1

The RBC deficiency is deficiency disease of:

View answer and explanation

Correct option: C

\mathrm{Vitamin }{B_{12}}

Option C (

\mathrm{Vitamin }{B_{12}}

) is correct because Vitamin B12 deficiency leads to megaloblastic anemia, which is characterized by a deficiency in red blood cells (RBCs).

17 Medium

17 of 191

Application +4 | -1

The correct, observation in the following reactions, is

\mathrm{Sucrose}\xrightarrow[{\mathrm{Cleavage}\,\mathrm{(Hydrolysis)}}]{{\mathrm{Glycosidic}\,\mathrm{bond}}}A + B\xrightarrow[{\mathrm{reagent}}]{{\mathrm{Seliwanoffs}}}

View answer and explanation

Correct option: C

Formation of red colour

Option C (Formation of red color) is correct because Seliwanoff's reagent tests for ketoses, and fructose (produced from sucrose hydrolysis) gives a red color.

18 Easy

18 of 191

Remembering +4 | -1

Simple proteins bonded with a non-proteinic prosthetic group (acting as cofactor) are called:

View answer and explanation

Correct option: B

Conjugated proteins

Option B (Conjugated proteins) is correct because they consist of a simple protein and a non-protein prosthetic group.

19 Medium

19 of 191

Remembering +4 | -1

A chemical substance acts as the currency of energy metabolism in a cell. It is:

View answer and explanation

Correct option: A

Adenosine triphosphate

Option A (Adenosine triphosphate) is correct because ATP is the primary energy currency of the cell, providing energy for various cellular processes.

20 Hard

20 of 191

Application +4 | -1

Specific rotation for

\alpha

-anomer of a given mono saccharide is

100^{\circ}

for

\beta

-anomer is

+20^{\circ}.

Specific rotation of equilibrium mixture is

68^{\circ},

\%

\alpha

anomer is

x \times 10 \%

then

{x}

View answer and explanation

Correct option: A

Option A (6) is correct because the percentage of the alpha anomer is 60%, and x is defined as the percentage divided by 10.

21 Easy

21 of 191

Analyzing +4 | -1

Which of the following reactions could not be explained on the basis of open chain structure of glucose?

View answer and explanation

Correct option: A

Pentaacetate of glucose does not react with

{NH}_2 {OH}

Option A (Pentaacetate of glucose does not react with

{NH}_2 {OH}

) is correct because it indicates the absence of a free aldehyde group, which contradicts the open-chain structure.

22 Easy

22 of 191

Remembering +4 | -1

The enzyme present in saliva is:

View answer and explanation

Correct option: D

Ptyalin

The correct answer is D (Ptyalin) because ptyalin, also known as salivary amylase, is the enzyme present in saliva that begins the digestion of starch.

23 Hard

23 of 191

Understanding +4 | -1

Assertion: Complementary base pairing occurs in DNA.

Reason: This is because adenine is combined with cytosine with a double bond and guanine is combined with thymin with a triple bond.

View answer and explanation

Correct option: C

If Assertion is correct but Reason is incorrect.

Option C is correct because while complementary base pairing does occur in DNA, the specific pairings and bond types mentioned in the reason are incorrect.

24 Easy

24 of 191

Analyzing +4 | -1

Which differs from the rest?

View answer and explanation

Correct option: A

Glucose

Option A (Glucose) is correct because glucose is a monosaccharide, while maltose, sucrose, and lactose are disaccharides.

25 Easy

25 of 191

Understanding +4 | -1

Glucose reacts with acetic anhydride to form:

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Correct option: C

Penta acetate

Option C (Penta acetate) is correct because glucose has five hydroxyl groups (-OH) which can react with acetic anhydride to form five ester linkages, resulting in a pentaacetate derivative.

26 Medium

26 of 191

Remembering +4 | -1

A saturated fatty acid found in oils and fats is:

View answer and explanation

Correct option: A

Palmitic acid

Option A (Palmitic acid) is correct because palmitic acid is a saturated fatty acid commonly found in oils and fats.

27 Easy

27 of 191

Understanding +4 | -1

Glucose and fructose differ in:

View answer and explanation

Correct option: D

Direction of optical rotation

Option D (Direction of optical rotation) is correct because glucose and fructose are isomers that differ in the direction they rotate plane-polarized light.

28 Hard

28 of 191

Understanding +4 | -1

Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Amylose is insoluble in water.
Reason R : Amylose is a long linear molecule with more than 200 glucose units. In the light of the above statements, choose the correct answer from the options given below.

View answer and explanation

Correct option: D

A is not correct but R is correct

Option D (A is not correct but R is correct) is correct because amylose is actually soluble in hot water, and the reason correctly states that amylose is a long linear molecule with more than 200 glucose units.

29 Hard

29 of 191

Application +4 | -1

when sucrose is subjected to acetylated the molecular weight will be increased by how many units with respective molecular weight of sucrose

View answer and explanation

Correct option: A

336

Option A (336) is correct because sucrose has 8 free hydroxyl groups, and each acetylation adds an acetyl group (CH3CO) with a molecular weight of 42, replacing a hydrogen (1). So, the molecular weight increases by (42-1)*8 = 328. However, the question is asking for the increase in molecular weight with *respective* molecular weight of sucrose, which is 342. Therefore the increase is 42*8 = 336.

30 Easy

30 of 191

Remembering +4 | -1

Which of the following test is not used for testing of proteins?

View answer and explanation

Correct option: B

Molish’s test

Option B (Molish’s test) is correct because it is used for detecting carbohydrates, not proteins.

Revision notes and key takeaways

Review BIOMOLECULES in your textbook or class notes, then use this set to check your understanding.

Key Takeaways

✓ This set contains 191 single-correct-answer MCQs on BIOMOLECULES.
✓ Try each question before opening its answer. Read the explanation where one is available.
✓ Sign in to save submitted answers. Revisit incorrect answers alongside your textbook or class notes.

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