C3 and C4 pathways, photorespiration
- Which of the following statements about RuBisCO is true? Answer: 4. It catalyzes the carboxylation of RuBP. Key idea: RuBisCO is the carboxylating enzyme of the Calvin cycle. It catalyses carboxyla... 1
- Given below are two statements:Statement I : In C_3 plants, some O_2 binds to RuBisCO, hence CO_2 fixation is decreased.Statement II : In C_4 plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespira… Answer: 4. Statement I is true but Statement II is false Key idea: O₂ competes with CO₂ for RuBisCO in C₃ plants, but C₄ plants avoid photor... 1
- Which of the following are required for the dark reaction of photosynthesis?A. LightB. ChlorophyllC. CO_2D. ATPE. NADPHChoose the correct answer from the options given below: Answer: 4. C, D and E only Key idea: the dark (biosynthetic) reaction uses the ATP and NADPH made in the light reaction, together with CO₂ .... 1
- How many molecules of ATP and NADPH are required for every molecule of CO_2 fixed in the Calvin cycle? Answer: 1. 3 molecules of ATP and 2 molecules of NADPH Key idea: fixing one CO₂ in the Calvin cycle costs 3 ATP and 2 NADPH. One CO₂ joins R... 1
- How many ATP and NADPH_2 are required for the synthesis of one molecule of Glucose during Calvin cycle? Answer: 3. 18 ATP and 12 NADPH ₂ Key idea: One CO₂ fixed in the Calvin cycle needs 3 ATP and 2 NADPH. Glucose has 6 carbons, so 6 turns are... 1
- What is the role of large bundle shealth cells found around the vascular bundles in C_4 plants ? Answer: 3. To increase the number of chloroplast for the operation of Calvin cycle The large bundle sheath cells of C₄ plants hold many chlo... 1
- Given below are two statements :Statement I :The primary CO_2 acceptor in C_4 plants is phosphoenolpyruvate and is found in the mesophyll cells.Statement II :Mesophyll cells of C_4 plants lack RuBisCo enzyme.In the light of the above statements, choo… Answer: 2. Both Statement I and Statement II are correct Statement I: in C₄ plants PEP, a three-carbon compound, is the primary CO₂ acceptor... 1
- Match List - I with List - II.List - I | List - II(a) Cohesion | (i) More attraction in liquid phase(b) Adhesion | (ii) Mutual attraction among water molecules(c) Surface tension | (iii) Water loss in liquid phase(d) Guttation | (iv) Attraction towar… Answer: 1. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii) Match the terms with their meanings: Cohesion is mutual attraction among water molecules:... 1
- The first stable product of CO_2 fixation in sorghum is : Answer: 2. Oxaloacetic acid Sorghum is a C4 plant. Its mesophyll cells fix CO ₂ with PEP carboxylase, so the first stable product is a 4-car... 1
- The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of : Answer: 2. 1 molecule of 3-C compound Key idea: In photorespiration RuBisCO acts as an oxygenase on RuBP. RuBP (5C) plus O₂ gives one molecu... 1
- Phosphoenol pyruvate (PEP) is the primary CO_2 acceptor in : Answer: 1. C₄ plants Key idea: The first CO₂ acceptor differs in C3 and C4 plants. In C₄ plants, phosphoenol pyruvate (PEP) in the mesophyll... 1
- The process which makes major difference between C_3 and C_4 plants is Answer: 2. photorespiration The big difference is photorespiration. In C₃ plants RuBisCO also acts as an oxygenase, causing a loss of fixed... 1
- A plant in your garden avoids photorespiratory losses, has improved water use efficiency, shows high rates of photosynthesis at high temperatures and has improved efficiency of nitrogen utilisation. In which of the following physiological groups woul… Answer: 2. C ₄ The listed features are the hallmarks of C₄ plants. C₄ plants have Kranz anatomy and PEP carboxylase, which fixes CO₂ in meso... 1