Reason : The resistance is generally produced due to
extrachromosomal genes present in plasmids.
- Assertion : Citric acid was the first organic acid to be
produced from the microbial fermentation in starchy and
sugary medium.
Reason : Rancidity of butter is due to formation of citric acid. - Assertion : Rennet is an extract from the stomach of calf
that contains enzyme rennin.
Reason : Rennet is added in detergents for removing oily stains
from laundry. - Assertion : A high Biochemical Oxygen Demand (BOD)
indicates the presence of large number of microorganisms
in a water body which suggests a high level of pollution.
Reason : BOD is the amout of oxygen taken up by microorganisms
that decompose organic waste matter in water. - Assertion : The excreta of cattle is used for the generation
of biogas, commonly called gobar gas.
Reason : Methanogens, which grow aerobically on cellulose
material help in the production of gobar gas. - Assertion : Nucleopolyhedrovirus has been shown to have
no negative impacts on plants, mammals, birds, fish or even
on non-target insects.
Reason : Nucleopolyhedrovirus is excellent genus for species
specific narrow spectrum insecticidal applications.
Short Answer Type Questions
- Milk starts to coagulate when lactic acid bacteria (LAB) is
added to warm milk as a starter. Mention any other two
benefits LAB provides. - What does “leg” in leghaemoglobin refer to? Why is this
pigment called oxygen-scavenger? - Explain various methods used for carrying out fermentation
process. - Describe the steps involved in the production of an
antibiotic. - (i) How is activated sludge produced during sewage
treatment?
(ii) Explain how this sludge is used in biogas production. - Compare biocontrol agents and biofertilisers.
- Explain the scientific reason for growing Azolla pinnata in the
rice field..
Answer Key
New MCQs- (c) 2. (b) 3. (c) 4. (b) 5. (b)
- (b) 7. (d) 8. (d) 9. (c) 10. (d)
- (a) 12. (d) 13. (c) 14. (d) 15. (a)
Exam Section- (b) 2. (c) 3. (d) 4. (b) 5. (d)
- (d) 7. (b) 8. (c) 9. (d) 10. (b)
- (c) 12. (b) 13. (a) 14. (a) 15. (d)
- (c) 17. (a) 18. (c) 19. (d) 20. (c)
- (c) 22. (b) 23. (a) 24. (b) 25. (c)
- (c) 27. (c) 28. (d) 29. (b) 30. (a)
Assertion & Reason- (b) 2. (b) 3. (d) 4. (c) 5. (a)
- (c) 7. (a)
Short Answer Type Questions- Two benefits provided by LAB are :
(i) It increases nutritional quality of curd by increasing
vitamin B 12 content.
(ii) It checks the growth of disease-causing organisms in the
gut. - The ‘leg’ in leghaemoglobin refers to leguminous plants. The
leghaemoglobin is referred to as oxygen scavanger because
it combines rapidly with O 2 to avoid any inhibitory effect of
oxygen on the enzyme nitrogenase. - Fermentation can be done using three different methods:
(i) Batch culture : In the batch culture, the conditions are set
up and not changed from outside once the fermentation
starts; for example, no more nutrients are added. This
is why the process is described as a closed system. The
process is stopped once sufficient product has been
formed. The contents of the fermenter are then removed,
the product isolated, the microorganism discarded and
the fermenter is cleaned and set up for a fresh batch.
(ii) Continuous culture : Continuous culture involves
continuous long-term operation over many weeks,
during which nutrient medium is added as fast as it is
used, and the overflow is harvested. Although this is
closer to the situation in natural environments, such
as the gut, continuous culture has found only limited
application. However, it is used for the production of
single cell protein where a large biomass of cells is
required.
(iii) Fed-batch culture : This is a compromise between the
two systems. With fed-batch culture more control of
the process is involved than with batch culture. The
period of growth is extended by adding nutrients
at low concentrations during the fermentation, and
not adding all the nutrients at the beginning. One
advantage of this is that the rate of growth can be
regulated to keep pace with the rate at which oxygen
can be supplied. The process is commonly used to
produce yeast cells for the baking industry.