Biology 2 Marks Questions

(i) Streptokinase is used to dissolve blood clots that have formed in the blood vessels. It is used immediately after symptoms of a heart attack occur to improve patient survival. This medicine may also be used to treat blood clots in the lungs (pulmonary
embolism) and in the legs (deep venous thrombosis).
(ii) Lactic acid is used as a food preservative, curing agent, and flavoring agent. It is an ingredient in processed foods and is used as a decontaminant during meat processing.
(iii) Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as a side-effect.

A-Spermatogonium
B-Primary spermatocyte
C-Secondary spermatocyte
D-Spermatid
E-Spermatozoa
F-Sertoli cell

One of the male gametes fuses with the female gamete and forms the embryo. The embryo subsequently develops into a new
plant. Another male gamete fuses with polar nuclei and eventually forms endosperm. Endosperm supplies food to the developing
embryo.

i. When an inducer, e.g., lactose binds to the repressor, the repressor is inactivated.
ii. The transcription of lac mRNA stops when lactose becomes exhausted or when there is no need for energy to the cells.
iii. β-galactosidase.

Flocs are masses of bacteria held together by slime and fungal filaments to form mesh like structures. They are formed during the secondary treatment of sewage.
Consume major part of organic matter in the effluent/lower BOD significantly/reduces polluting potential.