Which of the following statements is incorrect?
1. RuBisCO is a bifunctional enzyme
2. In C4 plants, the site of RuBisCO activity is mesophyll cell
3. The substrate molecule for RuBisCO activity is a 5-carbon compound
4. RuBisCO action requires ATP and NADPH
Identify the incorrect comparison between C3 and C4 photosynthetic plants:
| Characteristic | C3 plants | C4 plants | |
| 1. | Chloroplasts | One type [only granal] | Two types [granal and agranal] |
| 2. | Photorespiration | High | Negligible |
| 3. | First CO2 fixation product | 3-PGA | OAA |
| 4. | Carboxylase enzyme | Only RuBisCO | Only PEPcase |
| 1. | a 3-carbon molecule phosphoenol pyruvate (PEP) and is present in the mesophyll cells. |
| 2. | a 3-carbon molecule phosphoenol pyruvate (PEP) and is present in the bundle sheath cells. |
| 3. | a 5-carbon molecule RuBP and is present in the mesophyll cells. |
| 4. | a 5-carbon molecule RuBP and is present in the bundle sheath cells. |
| 1. | phosphoglyceric acid in the bundle sheath cells |
| 2. | phosphoglyceric acid in the mesophyll cells |
| 3. | oxaloacetate, by the carboxylation of phosphoenol pyruvate (PEP) in the mesophyll cells |
| 4. | oxaloacetate, by the carboxylation of phosphoenol pyruvate (PEP) in the bundle sheath cells |
| I. | Initially fix carbon dioxide in mesophyll cells as 4-carbon long compounds. |
| II. | Calvin cycle takes place in mesophyll cells |
| 1. | Only I is correct |
| 2. | Only II is correct |
| 3. | Both I and II are correct |
| 4. | Both I and II are incorrect |
| Assertion (A): | C4 plants are more efficient than C3 plants in hot, dry tropical environments. |
| Reason (R): | C4 plants have a specialized mechanism that increases the efficiency of photosynthesis by concentrating CO2 in bundle sheath cells, reducing photorespiration. |
| 1. | Both (A) and (R) are True and (R) correctly explains (A) |
| 2. | Both (A) and (R) are True and (R) does not correctly explain (A) |
| 3. | (A) is True; (R) is False |
| 4. | (A) is False; (R) is True |
| I: | Current availability of carbon dioxide levels is limiting to the C4 plants. |
| II: | C3 plants have a much lower temperature optimum than C4 plants. |
| 1. | Only I is correct | 2. | Only II is correct |
| 3. | Both I and II are correct | 4. | Both I and II are incorrect |