Q4. Arrange biogas, citric acid, penicillin and curd in decreasing order of their importance for the welfare of human society, giving reasons. (NCERT Exercise 14, page 160.)
NCERT asks for a reasoned view, so more than one order can be defended. One order: penicillin (an antibiotic that treats deadly diseases and saves lives), curd (daily food of better nutritional quality, with lactic acid bacteria that check disease-causing microbes in the stomach), biogas (fuel for cooking and lighting in rural areas), citric acid (an industrial chemical) (NCERT pages 151–156; the order is our reasoning).
Q5. What does the word antibiotic mean, and why does NCERT call antibiotics ‘pro life’?
‘Anti’ means against and ‘bio’ means life: against life, in the context of disease-causing organisms. For human beings, though, they are ‘pro life’, because they protect us from those organisms (NCERT page 152).
Q6. Which enzymes help detergents remove oily stains?
Lipases (NCERT page 153).
Q7. Why is cyclosporin A given to organ-transplant patients?
It is an immunosuppressive agent: it suppresses the immune response that would otherwise reject the transplanted organ (NCERT page 153; on graft rejection, see NCERT Section 7.2, page 136).
Q8. Which microbe makes lactic acid industrially, and which makes butyric acid?
Lactic acid: the bacterium Lactobacillus; butyric acid: the bacterium Clostridium butylicum (NCERT page 153).