CIE Biology Paper-4: Specimen Questions with Answers 81 - 82 of 120

Question number: 81

Essay Question▾

Describe in Detail

What is the importance of sulphur in living organisms. Discuss sulfur cycle?


Sulfur is most abundant element, which comprises many vitamins, proteins and hormones that play important role in climate and ecosystem. The majority of the Earth’s sulfur is stored underground in rocks and minerals, including as sulfate salts buried deep within ocean sediments.

The sulphur cycle contains both atmospheric and terrestrial processes. The cycle starts with the weathering of rocks, releasing the stored sulfur. Then it meets air where it is converted into sulfate. The sulfate is taken up by plants and microorganisms and is converted into organic forms; animals then consume these organic forms through foods they eat, thereby moving the sulfur through the food chain. As organisms die and decompose, some of the sulfur is again released as a sulfate and some enters the tissues of microorganisms. Due to natural sources that emit sulfur directly into the atmosphere, including volcanic eruptions, the breakdown of organic matter in swamps and tidal flats, and the evaporation of water.

Image shows sulphur cycle

Image Shows Sulphur Cycle

Image shows sulphur cycle, which contains in both atmospheric and terrestrial regions

Question number: 82

Essay Question▾

Describe in Detail

Described a rod shaped bacteria with the help of an example.


The example of rod shaped bacteria is –TMV Tobacco mosaic virus

  • It is a positive-sense single stranded RNA virus that infects a wide range of plants mainly tobacco
  • Its capsid is made from 2130 molecules of coat protein and one molecule of genomic single strand RNA, 6400 bases long
  • The coat protein self-assembles into the rod like helical shape around the RNA, which forms a hairpin loop structure.
Figure shows schematic model of TMV

Figure Shows Schematic Model of TMV

Figure shows schematic model of TMV in which 1 part is nucleic acids and 2 part is protomer