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46
Subjective

Amino acids behave like salts rather than simple amines or carboxylic acids. Explain.

Explanation

Amino acids have acidic COOH group as well as $\mathrm{NH}_2$ group hence, COOH looses its H to $\mathrm{NH}_2$, hence they exist as Z witter ion.

47
Subjective

Structures of glycine and alanine are given below. Show the peptide linkage in glycylalanine.

Explanation

Glycine and alanine on reaction with each other produces glycylalanine as

48
Subjective

Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to a physical change like change in temperature or a chemical change like, change in pH , denaturation of protein takes place. Explain the cause.

Explanation

Due to physical and chemical change, hydrogen bonds in proteins are disturbed. Due is this globules unfold and helix gets uncoiled and therefore, protein loses its biological activity. This is known as denaturation of proteins.

49
Subjective

Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ $\mathrm{mol}^{-1}$, while the activation energy is only $2.15 \mathrm{~kJ} \mathrm{~mol}^{-1}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.

Explanation

Enzymes, the biocatalysts reduce the magnitude of activation energy by providing alternative path. In the hydrolysis of sucrose, the enzyme sucrase reduces the activation energy from $6.22 \mathrm{~kJ} \mathrm{~mol}^{-1}$ to $2.15 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

50
Subjective

How do you explain the presence of an aldehydic group in a glucose molecule?

Explanation

Glucose on reaction with bromine water produces gluconic acid. This indicates the presence of CHO group.