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

1 / 15
1. Which of the following is a polysaccharide?
A. Glucose
B. Fructose
C. Cellulose
D. Ribose

Solution: Cellulose is a polymer of glucose units.

2 / 15
2. Which enzyme is used in the digestion of proteins?
A. Amylase
B. Lipase
C. Pepsin
D. Maltase

Solution: Pepsin digests proteins into peptides.

3 / 15
3. When converting a disaccharide to monosaccharides, which bond is hydrolyzed?
a) Disulfide bond
b) Glycosidic bond
c) Phosphodiester bond
d) Hydrogen bond

4 / 15
4. The linkage between two amino acids in a protein is:
A. Glycosidic bond
B. Peptide bond
C. Hydrogen bond
D. Phosphodiester bond

Solution: Amino acids are joined by peptide bonds.

5 / 15
5. 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

6 / 15
6.
Consider the following statements regarding biomolecules and select the correct option:
(1) All monosaccharides are reducing sugars and undergo mutarotation.
(2) Glycogen and cellulose both have α-(1→4) glycosidic linkages.
(3) In proteins, peptide bond has partial double bond character due to resonance.
(4) DNA contains uracil while RNA contains thymine.
(5) All enzymes are proteins but all proteins are not enzymes.
A. (1), (3) and (5) only
B. (1), (2) and (4) only
C. (2), (3) and (5) only
D. (3) and (5) only

Solution:
(1) False → Not all monosaccharides show mutarotation (e.g., keto forms may behave differently).
(2) False → Cellulose has β-(1→4), glycogen has α-(1→4) with α-(1→6) branching.
(3) True → Peptide bond shows resonance, hence planar.
(4) False → DNA has thymine, RNA has uracil.
(5) True (JEE context) → Enzymes are generally proteins.
✔ Correct set: (3), (5) only.

7 / 15
7. Which of the following is a reducing sugar?
A. Sucrose
B. Maltose
C. Lactose
D. Both B and C

Solution: Maltose and lactose have free aldehyde/ketone groups, so they are reducing sugars

8 / 15
8. Which vitamin is water-soluble?
A. Vitamin A
B. Vitamin D
C. Vitamin B₁₂
D. Vitamin K

Solution: Vitamin B-complex and C are water-soluble; others are fat-soluble.

9 / 15
9. Which base is present in RNA but not in DNA?
A. Adenine
B. Cytosine
C. Uracil
D. Guanine

Solution: RNA contains uracil instead of thymine.

10 / 15
10. A disaccharide is formed when two monosaccharides are bonded together by a bond.
a) glycosidic
b) peptide
c) ionic
d) phosphodiester

11 / 15
11. 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.

12 / 15
12. 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.

13 / 15
13. 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

14 / 15
14. 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.

15 / 15
15. 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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	DNA	RNA
Nitrogen bases	Adenine (A), thymine (T), cytosine (C), guanine (G)	Adenine (A), cytosine (C), guanine (G), uracil (U)

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