Biomolecules Class 12 Chemistry Free Online Mock Test 1

By admin / March 12, 2025

Class 12 Chemistry Online Free Mock Test

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Biomolecules Online Mock Test Class 12 Chemistry - 15 MCQs

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1. A disaccharide is formed when two monosaccharides are bonded together by a bond.

a) glycosidic

b) peptide

c) ionic

d) phosphodiester

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2. Which of the following statements about starch is incorrect?

a) It gives blue colour with iodine

b) It is a polymer of α-D-glucose

c) It is a reducing carbohydrate

d) It consists of branched chains

Explanation: Because it does not decrease Fehling’s solution or Tollen’s reagent, starch is a non-reducing saccharide. This means that all hemiacetal hydroxyl groups of glucose units are linked by glycosidic bonds and are not free.

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3. RNA lacks the nitrogen base of _______

a) Thymine

b) Cytosine

c) Uracil

d) Adenine

The nitrogen bases in DNA and RNA are adenine (A), cytosine (C), and guanine (G), but DNA also contains thymine (T) while RNA contains uracil (U) instead:

DNA

RNA

Nitrogen bases

Adenine (A), thymine (T), cytosine (C), guanine (G)

Adenine (A), cytosine (C), guanine (G), uracil (U)

The nitrogen bases are the only part of a nucleotide that varies. Nucleotides are the building blocks of DNA and RNA, and are made up of a sugar molecule, a phosphate group, and a nitrogenous base. The sugar molecule in DNA is deoxyribose, while in RNA it is ribose.

The nitrogen bases pair up in specific ways to form the genetic code:

DNA: Adenine pairs with thymine, and cytosine pairs with guanine. These pairs form hydrogen bonds with each other, giving DNA stability and flexibility.

RNA: Uracil pairs with adenine.

The correct pairing of these bases is essential for biological function. Changes to the nitrogenous base sequences in DNA can cause mutations that lead to diseases like sickle cell anemia.

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4. Which of the following chemical classes belong to the vast group of carbohydrates?

a) Polyhydroxy ketones

b) Polyhalo aldehydes

c) Polyamino aldehydes

d) Polyhydroxy carboxylic acids

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5. When converting a disaccharide to monosaccharides, which bond is hydrolyzed?

a) Disulfide bond

b) Glycosidic bond

c) Phosphodiester bond

d) Hydrogen bond

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6. Sucrose is a _____ chemical, and the hydrolysis product combination is ______in nature.

a) dextrorotatory; dextrorotatory

b) laevorotatory; laevorotatory

c) laevorotatory; dextrorotatory

d) dextrorotatory; laevorotatory

Explanation: Sucrose is a dextrorotatory sugar that produces a combination of dextrorotatory glucose and laevorotatory fructose when hydrolyzed. The resultant mixture is laevorotatory because the specific rotation of fructose is larger than that of glucose.

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7. Which of the following statements about metabolism is false?

a) It is due to this process that biomolecules do not have a turnover

b) It involves the formation of biomolecules

c) It involves the breaking down of biomolecules

d) It involves various chemical reactions

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8. Which of the following statements about maltose is incorrect?

a) It consists of two glucopyranose units

b) It is a disaccharide

c) Glycosidic bond between C1 of one unit and C4 of the other unit

d) It is a non-reducing sugar

Explanation: The free aldehyde group, which has reducing capabilities, can be formed at the C1 carbon of the second -D-glucose unit in solution. As a result, it decreases sugar.

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	DNA	RNA
Nitrogen bases	Adenine (A), thymine (T), cytosine (C), guanine (G)	Adenine (A), cytosine (C), guanine (G), uracil (U)

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