- 1(current)
Q. No.The enzyme RuBisCO shows dual affinity for:
1. \(\mathrm{O}_2~\text {and }\mathrm{H}_2 \mathrm{O} \)
2. \(\mathrm{CO}_2~ and ~\mathrm{O}_2\)
3. ATP and NADPH
4. RuBP and PGA
1. \(\mathrm{O}_2~\text {and }\mathrm{H}_2 \mathrm{O} \)
2. \(\mathrm{CO}_2~ and ~\mathrm{O}_2\)
3. ATP and NADPH
4. RuBP and PGA
Subtopic: Photorespiration |
92%
Level 1: 80%+
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Photorespiration is considered a wasteful process because:
1. It occurs only in darkness
2. It produces ATP but no NADPH
3. It consumes \(O_2\) and releases \(CO_2\)without synthesising sugars
4. It directly inhibits glycolysis
1. It occurs only in darkness
2. It produces ATP but no NADPH
3. It consumes \(O_2\) and releases \(CO_2\)without synthesising sugars
4. It directly inhibits glycolysis
Subtopic: Photorespiration |
91%
Level 1: 80%+
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"RuBisCO's oxygenase activity, which leads to photorespiration, is a harmful mutation that reduces photosynthetic efficiency by approximately 50%, but plants have been unable to evolve a solution to this problem over millions of years."
1. True
2. False
1. True
2. False
Subtopic: Photorespiration |
Level 3: 35%-60%
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\(C_4\) plants minimise photorespiration because:
1. They perform photosynthesis in the absence of \(O_2\)
2. PEP carboxylase, their primary \(CO_2\)-fixing enzyme, has no affinity for \(O_2\)
3. Their mesophyll cells lack chloroplasts
4. They fix \(CO_2\) only during the night
1. They perform photosynthesis in the absence of \(O_2\)
2. PEP carboxylase, their primary \(CO_2\)-fixing enzyme, has no affinity for \(O_2\)
3. Their mesophyll cells lack chloroplasts
4. They fix \(CO_2\) only during the night
Subtopic: Photorespiration |
80%
Level 1: 80%+
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Biochemists studied RuBisCO enzyme under different conditions:
Condition 1: \(25^\circ C\), high \(CO_2\)(1000 ppm), low \(O_2\)(2%)
- Carboxylase activity: High
- Oxygenase activity: Very low
- Net photosynthesis: Maximum
Condition 2: \(35^\circ C\), low \(CO_2\)(200 ppm), high \(O_2\)(21%)
- Carboxylase activity: Moderate
- Oxygenase activity: High
- Net photosynthesis: Significantly reduced
Condition 3: \(35^\circ C\), high \(CO_2\)(1000 ppm), high \(O_2\)(21%)
- Carboxylase activity: High
- Oxygenase activity: Moderate
- Net photosynthesis: Good
Based on these results, what is the most critical factor determining RuBisCO's efficiency in photosynthesis?
1. Only temperature determines enzyme efficiency; high temperature always reduces net photosynthesis
2. \(CO_2/O_2\) ratio at active site determines carboxylase v/s oxygenase activity; both compete for binding
3. Oxygen conc. alone determines photorespiration rate; \(CO_2\) levels have no impact on enzyme specificity
4. RuBisCO activity depends only on enzyme conc.; substrate availability plays no regulatory role
Condition 1: \(25^\circ C\), high \(CO_2\)(1000 ppm), low \(O_2\)(2%)
- Carboxylase activity: High
- Oxygenase activity: Very low
- Net photosynthesis: Maximum
Condition 2: \(35^\circ C\), low \(CO_2\)(200 ppm), high \(O_2\)(21%)
- Carboxylase activity: Moderate
- Oxygenase activity: High
- Net photosynthesis: Significantly reduced
Condition 3: \(35^\circ C\), high \(CO_2\)(1000 ppm), high \(O_2\)(21%)
- Carboxylase activity: High
- Oxygenase activity: Moderate
- Net photosynthesis: Good
Based on these results, what is the most critical factor determining RuBisCO's efficiency in photosynthesis?
1. Only temperature determines enzyme efficiency; high temperature always reduces net photosynthesis
2. \(CO_2/O_2\) ratio at active site determines carboxylase v/s oxygenase activity; both compete for binding
3. Oxygen conc. alone determines photorespiration rate; \(CO_2\) levels have no impact on enzyme specificity
4. RuBisCO activity depends only on enzyme conc.; substrate availability plays no regulatory role
Subtopic: Photorespiration |
92%
Level 1: 80%+
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Photorespiration involves all of the following organelles EXCEPT:
1. Chloroplast
2. Peroxisome
3. Mitochondria
4. Golgi apparatus
1. Chloroplast
2. Peroxisome
3. Mitochondria
4. Golgi apparatus
Subtopic: Photorespiration |
89%
Level 1: 80%+
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Photorespiration involves the consumption of:
1. Neither oxygen nor carbon dioxide in the overall process
2. Carbon dioxide and release of oxygen with ATP synthesis
3. Both oxygen and carbon dioxide with net gain of ATP
4. Oxygen and release of carbon dioxide without ATP synthesis
1. Neither oxygen nor carbon dioxide in the overall process
2. Carbon dioxide and release of oxygen with ATP synthesis
3. Both oxygen and carbon dioxide with net gain of ATP
4. Oxygen and release of carbon dioxide without ATP synthesis
Subtopic: Photorespiration |
84%
Level 1: 80%+
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The C4 pathway is advantageous because it:
| 1. | Occurs in mesophyll cells only |
| 2. | Minimises photorespiration in plants |
| 3. | Requires less light intensity |
| 4. | Produces more oxygen molecules |
Subtopic: C4 Cycle (Hatch & Slack Pathway) | Photorespiration |
92%
Level 1: 80%+
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Photorespiration results in:
1. Net synthesis of ATP and sugars
2. Increased CO2 fixation efficiency
3. Release of CO2 with consumption of ATP
4. Formation of NADPH
1. Net synthesis of ATP and sugars
2. Increased CO2 fixation efficiency
3. Release of CO2 with consumption of ATP
4. Formation of NADPH
Subtopic: Photorespiration |
92%
Level 1: 80%+
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Which of the following statements regarding photorespiration is correct?
| 1. | It occurs only in C₄ plants |
| 2. | It increases photosynthetic efficiency |
| 3. | It involves chloroplast, peroxisome and mitochondrion |
| 4. | It produces ATP |
Subtopic: Photorespiration |
93%
Level 1: 80%+
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- 1(current)
Q. No.
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