▶️ Answer/Explanation
Solution
(a)
Explanation: The lock and key hypothesis can be illustrated as follows:
- Diagram 1: Lysozyme (the “lock”) with a specifically shaped active site.
- Diagram 2: Peptidoglycan (the “key”) with a complementary shape binding to the active site, forming an enzyme-substrate complex.
- Diagram 3: Hydrolysis of glycosidic bonds in peptidoglycan, yielding products NAG and NAM.
Annotations: Label the active site, substrate (peptidoglycan), and products (NAG and NAM). Water molecules may be shown as participating in the hydrolysis.
(b)
Similarities:
- Both lysozyme and penicillin target the bacterial cell wall (peptidoglycan), leading to cell lysis.
- Both weaken the cell wall, making bacteria susceptible to osmotic pressure.
Differences:
- Lysozyme is an enzyme that directly hydrolyzes glycosidic bonds in peptidoglycan.
- Penicillin is a β-lactam antibiotic that inhibits transpeptidase, preventing cross-link formation in peptidoglycan synthesis.
- Lysozyme is effective at all bacterial growth stages, while penicillin only works during active cell wall synthesis.
- Lysozyme is a protein (denaturable), whereas penicillin is a small molecule resistant to heat.