Biomolecules

  • Question 1
    CBSEENCH12009461

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

    Solution

    Molecules which have polar nature are capable to form hydrogen bond are generally soluble in water. In sucrose and glucose hydroxyl groups are present, which is polar in nature. Therefore, they are involved in intermolecular hydrogen bonding with water molecules, so these compounds are readily soluble in water. On other hand benzene and cyclohexane are hydrocarbons. They do not have any polar group so they cannot make hydrogen bonds with water. 

    Question 2
    CBSEENCH12009462

    What are the expected products of hydrolysed of lactose?

    Solution
    Upon hydrolysis, lactose gives equivalent amounts of D(+) glucose and D(+) galactose.


    Question 3
    CBSEENCH12009463

    How do you explain the absence of aldehyde group in the penta acetate of D-glucose?

    Solution

    Glucose reacts with hydroxylamine to form an oxime. where as, the penta acetate of glucose does not react with hydroxyl amine indicating the absence of free CHO group.

    Question 4
    CBSEENCH12009464

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

    Solution

    Amino acids are dipolar in nature (+NH3-CHR-COO-) and have strong dipolar interaction. Amino acids have amino (basic) group and carboxylic (acidic) group. A proton which comes from carboxylic group is accepted by amino group. Thus amino acid exists in the form of Zwitter ion.


    Due to this ionic form, amino acids become crystalline solids and due to this salt like structure, show higher melting point.

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