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Practice each question, then open the answer or worked solution.
Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six-membered ring compounds) are insoluble in water. Explain.
Answer: Glucose and sucrose have several -OH groups, allowing them to form hydrogen bonds with water, making them soluble. Cyclohexane and benzene do not have -OH groups, so they cannot form hydrogen bonds and remain insoluble in water.
What are the expected products of hydrolysis of lactose?
Answer: Lactose is made up of β-D-galactose and β-D-glucose. When lactose undergoes hydrolysis, it breaks down into these two simpler sugars.
How do you explain the absence of an aldehyde group in the pentaacetate of D-glucose?
The pentaacetate of D-glucose cannot react with hydroxylamine, showing it lacks a free aldehyde group.
Solution coming soon.
The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.
Amino acids form zwitterions in water, making them more soluble and increasing their melting points compared to halo acids.
Solution coming soon.
Where does the water present in the egg go after boiling the egg?
Answer: When eggs are boiled, their proteins denature and coagulate. The water gets absorbed by the coagulated proteins through hydrogen bonding.
Why cannot vitamin C be stored in our body?
Answer: Vitamin C is water soluble. Since water-soluble substances are regularly lost in urine, vitamin C cannot be stored in the body.
What products would be formed when a nucleotide from DNA containing thymine is hydrolyzed?
Answer: On hydrolysis, such a nucleotide from DNA gives thymine, β-D-2-deoxyribose, and phosphoric acid.
When RNA is hydrolyzed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?
Random quantities of bases after RNA hydrolysis suggest RNA is single stranded.
Solution coming soon.
What are monosaccharides?
Answer: Monosaccharides are the simplest form of carbohydrates. They cannot be broken down into simpler sugars. Monosaccharides can be classified by the number of carbon atoms (e.g., pentose for 5 carbons) and by their functional group (aldoses have an aldehyde group, ketoses have a ketone group). For example, a 5-carbon ketone sugar = ketopentose.
What are reducing sugars?
Answer: Reducing sugars are carbohydrates that can reduce Fehling’s solution and Tollen’s reagent. All monosaccharides and most disaccharides, except sucrose, are reducing sugars.