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Q. No.The process where energy from electron transfer is used to create a proton gradient, which then drives ATP synthesis, is called
1. Chemiosmosis
2. Substrate-level phosphorylation
3. Glycolysis
4. Oxidative phosphorylation
1. Chemiosmosis
2. Substrate-level phosphorylation
3. Glycolysis
4. Oxidative phosphorylation
Subtopic: Chemiosmotic hypothesis |
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The chemiosmotic hypothesis (Mitchell) explains ATP synthesis as:
1. Substrate-level phosphorylation
2. Direct transfer of phosphate group
3. Utilisation of proton gradient across inner membrane
4. Breakdown of Acetyl-CoA
1. Substrate-level phosphorylation
2. Direct transfer of phosphate group
3. Utilisation of proton gradient across inner membrane
4. Breakdown of Acetyl-CoA
Subtopic: Chemiosmotic hypothesis |
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C.B. van Niel conducted his groundbreaking research on photosynthesis by studying which group of organisms?
1. Green algae in freshwater ponds
2. Chloroplasts isolated from spinach leaves
3. Cyanobacteria in marine environments
4. Purple sulphur bacteria in anaerobic conditions
1. Green algae in freshwater ponds
2. Chloroplasts isolated from spinach leaves
3. Cyanobacteria in marine environments
4. Purple sulphur bacteria in anaerobic conditions
Subtopic: Historical View: Experiments |
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What was van Niel's most significant contribution to understanding photosynthesis?
1. He discovered chlorophyll pigments in plants
2. He proved that oxygen comes from water, not carbon dioxide
3. He identified the Calvin cycle reactions
4. He measured the rate of photosynthesis using a spectrophotometer
1. He discovered chlorophyll pigments in plants
2. He proved that oxygen comes from water, not carbon dioxide
3. He identified the Calvin cycle reactions
4. He measured the rate of photosynthesis using a spectrophotometer
Subtopic: Historical View: Experiments |
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Purple sulphur bacteria studied by van Niel use hydrogen sulphide \((H_2S)\) during photosynthesis. What byproduct do they produce instead of oxygen?
1. Sulphuric acid \((H_2SO_4)\)
2. Carbon monoxide (CO)
3. Elemental sulphur (S)
4. Hydrogen gas \((H_2)\)
1. Sulphuric acid \((H_2SO_4)\)
2. Carbon monoxide (CO)
3. Elemental sulphur (S)
4. Hydrogen gas \((H_2)\)
Subtopic: Historical View: Experiments |
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Van Niel proposed a general equation for photosynthesis applicable to all photosynthetic organisms. What is this generalised form?
1. \(\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow\left(\mathrm{CH}_2 \mathrm{O}\right)+\mathrm{O}_2 \)
2. \(\mathrm{CO}_2+\mathrm{H}_2 \mathrm{~A} \rightarrow\left(\mathrm{CH}_2 \mathrm{O}\right)+\mathrm{A} \)
3. \(6 \mathrm{CO}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+6 \mathrm{O}_2 \)
4. \(\mathrm{H}_2 \mathrm{O}+ \text { light energy }\rightarrow \mathrm{H}_2+\mathrm{O}\)
1. \(\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow\left(\mathrm{CH}_2 \mathrm{O}\right)+\mathrm{O}_2 \)
2. \(\mathrm{CO}_2+\mathrm{H}_2 \mathrm{~A} \rightarrow\left(\mathrm{CH}_2 \mathrm{O}\right)+\mathrm{A} \)
3. \(6 \mathrm{CO}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+6 \mathrm{O}_2 \)
4. \(\mathrm{H}_2 \mathrm{O}+ \text { light energy }\rightarrow \mathrm{H}_2+\mathrm{O}\)
Subtopic: Historical View: Experiments |
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Van Niel's hypothesis about the source of oxygen was later confirmed in the 1940s using which experimental technique?
1. Electron microscopy of chloroplasts
2. Chromatography of photosynthetic pigments
3. Isotope labelings with \(_{1 }^{15} \mathrm{O}\) (heavy oxygen)
4. X-ray crystallography of photosystem proteins
1. Electron microscopy of chloroplasts
2. Chromatography of photosynthetic pigments
3. Isotope labelings with \(_{1 }^{15} \mathrm{O}\) (heavy oxygen)
4. X-ray crystallography of photosystem proteins
Subtopic: Historical View: Experiments |
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A botanist conducts an experiment where isolated thylakoid membranes are exposed to different wavelengths of light while monitocing both the oxidation state of P700 (the reaction eentre of PSI) and the production of ATP. The results reveal an intriguing pattern:
- Far-red light (>700 nm): P700 becomes highly reduced; minimal ATP production
- Red light ( 680 nm ): P700 becomes oxidised; significant ATP production
- Simultaneous far-red + red light: P700 maintains an intermediate oxidation state; ATP production exceeds the sum of individual wavelengths
This experimental outcome provides the strongest evidence for which fundamental principle of photosynthetic light reactions?
1. The chemiosmotic theory, demonstrating that ATP synthesis requires the establishment of a proton gradient across the thylakoid membrane, which is maximised when both wavelengths activate complementary components of the electron transport chain
2. The existence of two distinct photosystems working in series (Z-scheme), where far-red light preferentially excites PSI while red light preferentially excites PSII, and optimal electron flow requires balanced activation of both systems
3. The phenomenon of cyclic photophosphorylation, in which electrons from PSI return to the cytochrome bef complex under far-red illumination, generating ATP without net NADPH production or oxygen evolution
4. The principle of photosynthetic action spectrum matching, showing that chlorophyll a absorbs different wavelengths with varying efficiencies, directly affecting the quantum yield of photochemical reactions
- Far-red light (>700 nm): P700 becomes highly reduced; minimal ATP production
- Red light ( 680 nm ): P700 becomes oxidised; significant ATP production
- Simultaneous far-red + red light: P700 maintains an intermediate oxidation state; ATP production exceeds the sum of individual wavelengths
This experimental outcome provides the strongest evidence for which fundamental principle of photosynthetic light reactions?
1. The chemiosmotic theory, demonstrating that ATP synthesis requires the establishment of a proton gradient across the thylakoid membrane, which is maximised when both wavelengths activate complementary components of the electron transport chain
2. The existence of two distinct photosystems working in series (Z-scheme), where far-red light preferentially excites PSI while red light preferentially excites PSII, and optimal electron flow requires balanced activation of both systems
3. The phenomenon of cyclic photophosphorylation, in which electrons from PSI return to the cytochrome bef complex under far-red illumination, generating ATP without net NADPH production or oxygen evolution
4. The principle of photosynthetic action spectrum matching, showing that chlorophyll a absorbs different wavelengths with varying efficiencies, directly affecting the quantum yield of photochemical reactions
Subtopic: Light Reaction: Electron Transport |
Level 3: 35%-60%
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In Engelmann's experiment with Choolophora and a prism-spit light spectrum, which of the following observations correatly explains the relationship between light wavelength and photosynthetic activity?
1. Bacteria accumulated most in green region, showing maximum photosymthetic rate in green light.
2. Bacteria accumulated near the red and blue regions, showing maximum photosynthetic rate in those wavelengths.
3. Bacteria showed uniform distribution throughout the spectrum, indicating equal photosynthetic activity at all wavelengths.
4. Bacteria gathered near yellow region as yellow light is most effective in photosynthesis.
1. Bacteria accumulated most in green region, showing maximum photosymthetic rate in green light.
2. Bacteria accumulated near the red and blue regions, showing maximum photosynthetic rate in those wavelengths.
3. Bacteria showed uniform distribution throughout the spectrum, indicating equal photosynthetic activity at all wavelengths.
4. Bacteria gathered near yellow region as yellow light is most effective in photosynthesis.
Subtopic: Historical View: Experiments |
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The site of light reaction in chloroplast is the:
1. Stroma
2. Inter-membrane spoce
3. Outer memberne
4. Thylakoid membrane
1. Stroma
2. Inter-membrane spoce
3. Outer memberne
4. Thylakoid membrane
Subtopic: Light Reaction: Electron Transport |
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