More practice questions

3. Q3. A boiled enzyme no longer works, yet its amino-acid sequence is unchanged. Explain.

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   Boiling denatures the protein: its secondary and tertiary structures are destroyed, and with them the shape of the active site, but the primary structure, the sequence, stays intact (NCERT page 295 for denaturation; NCERT Class 11 Biology, page 116, for enzymes).

4. Q4. Name two enzymes that NCERT says act on sucrose, and the products.

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   Sucrase (NCERT Unit 10, page 295) and invertase (NCERT Unit 7, page 214); both hydrolyse sucrose to glucose and fructose: C₁₂H₂₂O₁₁ + H₂O → C₆H₁₂O₆ + C₆H₁₂O₆.

5. Q5. Repeat Example 1 at body temperature, 310 K. Is the factor larger or smaller than at 298 K?

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   e^{4070/(8.314 × 310)} = e^4070/2577 = e^1.579 ≈ 4.9, a little smaller than 5.2 at 298 K, because the same difference in activation energy matters less at a higher temperature (reasoned from NCERT Unit 3, page 79).

6. Q6. Why can a small amount of enzyme convert a large amount of substrate?

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   At the end of each cycle the enzyme releases the product unchanged and binds another substrate molecule, so the same enzyme molecule is used again and again (NCERT Class 11 Biology, page 116; NCERT page 295).