Biomolecules Quiz - ICSE Class 12 Chemistry

Free practice quiz: Biomolecules (ICSE Class 12 Chemistry). 48 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. The Zwitterionic form of an amino acid is characterized by:

   1. Presence of a free amino group and a free carboxyl group.
   2. Presence of a negatively charged amino group and a positively charged carboxyl group.
   3. Presence of a positively charged amino group and a negatively charged carboxyl group.
   4. Presence of a neutral amino group and a neutral carboxyl group.
   Show answer

   Answer: C. Presence of a positively charged amino group and a negatively charged carboxyl group.

   A Zwitterion is an internal salt formed by an amino acid where the amino group is protonated (positively charged, -NH3+) and the carboxyl group is deprotonated (negatively charged, -COO-) at physiological pH. This makes the overall molecule electrically neutral.

2. The complete hydrolysis of a complex carbohydrate (polysaccharide) like starch would yield which of the following monosaccharides?

   1. Fructose
   2. Galactose
   3. Glucose
   4. Sucrose
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   Answer: C. Glucose

   Starch is a polymer of glucose units linked by glycosidic bonds. Complete hydrolysis breaks all these bonds, yielding individual glucose molecules.

3. A competitive inhibitor of an enzyme typically:

   1. Binds to the allosteric site of the enzyme.
   2. Decreases the Vmax of the reaction.
   3. Binds to the active site of the enzyme, competing with the substrate.
   4. Is permanently bound to the enzyme.
   Show answer

   Answer: C. Binds to the active site of the enzyme, competing with the substrate.

   Competitive inhibitors are molecules that resemble the substrate and bind to the enzyme's active site. This binding prevents the substrate from accessing the active site, thus inhibiting the reaction. Competitive inhibition affects the Km but not the Vmax.

4. The tertiary structure of a protein is stabilized by various types of interactions between amino acid side chains. Which interaction is strongest in stabilizing the tertiary structure of a protein in a physiological environment?

   1. Hydrophobic interactions
   2. Ionic bonds
   3. Hydrogen bonds
   4. Disulfide bonds
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   Answer: D. Disulfide bonds

   Disulfide bonds are covalent bonds formed between sulfur atoms of cysteine residues. They are significantly stronger than non-covalent interactions like hydrophobic interactions, ionic bonds, and hydrogen bonds, making them the most potent stabilizers of tertiary protein structure.

5. The process of DNA replication results in the formation of two DNA molecules, each consisting of one original strand and one newly synthesized strand. This is known as:

   1. Conservative replication
   2. Dispersive replication
   3. Semi-conservative replication
   4. Random replication
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   Answer: C. Semi-conservative replication

   Semi-conservative replication means that each new DNA molecule consists of one strand from the parent DNA molecule and one newly synthesized strand, ensuring accurate inheritance of genetic information.

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