Ncert Chemistry Class 12 intext questions solutions chapter 10 Biomolecules

Biomolecules intext questions solutions: Class 12 Chemistry Chapter 10 intext questions solutions

Textbook	Ncert
Class	Class 12
Subject	Chemistry
Chapter	Chapter 10
Chapter Name	Biomolecules Class 12 intext questions solutions
Category	Intext questions
Medium	English

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Question 10.1: Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water. Explain.

Solution 10.1: Glucose and sucrose are soluble in water due to their ability to form hydrogen bonds with water molecules. Both glucose and sucrose contain multiple hydroxyl (-OH) groups, which can readily interact with water through hydrogen bonding. These interactions allow the sugar molecules to dissolve by forming strong attractions with water molecules, a polar solvent. Water’s polarity plays a key role in this solubility, as it surrounds and stabilizes the individual sugar molecules in solution.

On the other hand, cyclohexane and benzene are nonpolar compounds, consisting of simple six-membered rings without polar functional groups. Since water is a polar solvent, it tends to dissolve substances that can interact with its polar nature, primarily through hydrogen bonding or dipole interactions.

Cyclohexane and benzene, lacking polar groups, cannot form hydrogen bonds or meaningful dipole interactions with water. Instead, they exhibit strong London dispersion forces among themselves, making them more likely to remain insoluble in water. Thus, due to the “like dissolves like” principle, glucose and sucrose are water-soluble, whereas cyclohexane and benzene are not.

Question 10.2: What are the expected products of hydrolysis of lactose?

Solution 10.2: Lactose is composed of β-D galactose and β-D glucose. Thus, on hydrolysis, it gives β-D galactose and β-D glucose.

Question 10.3: How do you explain the absence of aldehyde group in the pentaacetate of D-glucose?

Solution 10.3: D-glucose reacts with hydroxylamine (NH₂OH) to form an oxime because of the presence of aldehydic (−CHO) group or carbonyl carbon. This happens as the cyclic structure of glucose forms an open chain structure in an aqueous medium, which then reacts with NH₂OH to give an oxime.

But pentaacetate of D-glucose does not react with NH₂OH. This is because pentaacetate does not form an open chain structure.

Question 10.4: The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.

Solution 10.4: Both acidic (carboxyl) as well as basic (amino) groups are present in the same molecule of amino acids. In aqueous solutions, the carboxyl group can lose a proton and the amino group can accept a proton, thus giving rise to a dipolar ion known as a zwitter ion.

Due to this dipolar behaviour, they have strong electrostatic interactions within them and with water. But halo-acids do not exhibit such dipolar behaviour.

For this reason, the melting points and the solubility of amino acids in water is higher than those of the corresponding halo-acids.

Question 10.5: Where does the water present in the egg go after boiling the egg?

Solution 10.5: After boiling an egg, the water inside the egg primarily gets absorbed into the proteins, which coagulate and form a solid structure. Some water also evaporates as steam, but most is trapped within the denatured protein network of the egg white and yolk.

Question 10.6: Why cannot vitamin C be stored in our body?

Solution 10.6: Vitamin C cannot be stored in our body because it is a water-soluble vitamin, meaning it dissolves in water and is easily excreted through urine. Therefore, the body cannot retain it for long periods.

Question 10.7: What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?

Solution 10.7: When a nucleotide from DNA containing thymine is hydrolyzed, it breaks down into three main products:

1. Nitrogenous Base: Thymine (a pyrimidine base).
2. Sugar: Deoxyribose (the sugar component of DNA).
3. Phosphate Group: One phosphate group.

These components can be further utilized in various biochemical processes.

Question 10.8: When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?

Solution 10.8: The fact that there is no fixed relationship among the quantities of different bases obtained when RNA is hydrolyzed suggests that the structure of RNA is more variable and less uniform than that of DNA. Specifically, this indicates:

1. Non-Complementary Pairing: Unlike DNA, where Adenine always pairs with thymine and cytosine always pairs with guanine in a specific ratio, RNA does not have a strict base-pairing rule. This leads to varying amounts of each base (adenine, guanine, cytosine, and uracil).
2. Diverse Functionality: RNA serves multiple functions (such as mRNA, tRNA, and rRNA) in protein synthesis and gene regulation, leading to different base compositions depending on the specific type of RNA and its role in the cell.
3. Single-Stranded Nature: RNA is typically single-stranded, allowing for a flexible structure that can adopt various shapes and configurations, further contributing to the variability in base composition.