Question

67-68. Refer to the diagram below. CH.DE Coo- CHOD CO -OH -OH + H Rutico - HOH - -OH CH00 do + H H 200 Carbon dioxide еное Ruose 15 bisphosphate RuBP) Sx-carbon skoloton of reaction intermediate 67. If a plant is removed from its natural environment and exposed to 100 percent CO, composed of radioisotope C, which of the following will not occur? a. All the carbon molecules in the RuBP molecules will eventually become 'c. b. Rubisco will eventually contain "c. c. Rubisco will cease to carboxylate RuBP. d. The rate of photorespiration will remain unchanged. e. Eventually all newly synthesized carbon-containing molecules in the plant will contain '"C 68. Irco, entered the Calvin cycle by directly combining with RuBP as shown in the diagram, this reaction is most likely occurring in: a. A CS plant b. A C6 plant c. A C4 plant d. A C3 plant e. None of the above

Answer 1

Q.67. Answer- c. Rubisco will cease to carboxylate RuBP

Explanation- Rubisco fix atmospheric carbon dioxide by combining it with RuBP and this reaction is dependent on CO2 concentration. At high CO2 concentration Rubisco maximally carry out carboxylation reaction to convert ribulose 1,5- bisphosphate into glyceraldehyde-3-phosphate. As the carbon is ​​​​​¹⁴C then after many cycles all carbon of Rubp will be radiolabled.

Q.68. Answer- d. a C3 plant

Explanation- Rubisco is the enzyme that can fix directly atmospheric carbon dioxide and fix it into organic molecule like sugar. When Rubisco fix carbon, three molecules of RuBP is converted into six molecules of three carbon sugar glyceraldehyde-3-phosphate and this is the first product of cycle so that this cycle is known as C3cycle and plants are known as C3 plants.