Photosynthesis MCQ Quiz in मल्याळम - Objective Question with Answer for Photosynthesis - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is In PS-II, the oxidation of two water molecules produces four electrons, four protons, & a single O₂.

Explanation:

1. Electron transport between PS-II to PS-I produces ATP by substrate level phosphorylation: This statement is incorrect. In non-cyclic photophosphorylation, ATP is generated through chemiosmosis, not substrate-level phosphorylation. ATP synthesis is driven by the proton gradient created by the movement of electrons through the electron transport chain (ETC), and protons flow through ATP synthase to produce ATP. Substrate-level phosphorylation is a different process (in glycolysis or the citric acid cycle), and it is not involved in the light reactions of photosynthesis.
2. In PS-II, the oxidation of two water molecules produces four electrons, four protons, & a single O₂: This statement is correct. In Photosystem II (PS-II), water molecules are split in a process called photolysis. For every two molecules of water, this results in the production of:
   1. One molecule of oxygen (O₂), which is released as a byproduct. This is the correct process that happens during photolysis in PS-II.
   2. Four protons (H⁺), which contribute to the proton gradient used for ATP synthesis.
   3. Four electrons (e⁻), which are used to replace the electrons lost from PS-II when it absorbs light.
3. Electrons from Photosystem II are passed directly to NADP+ to form NADPH: This statement is incorrect. In non-cyclic photophosphorylation, electrons from Photosystem II (PS-II) are not passed directly to NADP+. Instead, electrons from PS-II are passed through an electron transport chain (ETC) to Photosystem I (PS-I). After absorption of light by PS-I, the electrons are transferred to NADP+, reducing it to NADPH. The process involves two separate photosystems.
4. Electrons flow from Photosystem I to Photosystem II, generating NADPH and oxygen: This statement is incorrect. In the non-cyclic electron transport system, electrons flow from Photosystem II to Photosystem I, not the other way around. The flow of electrons from PS-II to PS-I leads to the formation of NADPH at PS-I, while the splitting of water molecules at PS-II produces oxygen as a byproduct.

Fig: Z scheme of light reaction

Concept:

Bacteria are unicellular prokaryotes that are placed in Kingdom Monera according to Whittaker's Five Kingdom System.

Depending on the mode of nutrition, bacteria are of two types - Autotrophs and Heterotrophs.

Autotrophic bacteria are further classified into Photosynthetic bacteria and Chemosynthetic bacteria.

Photosynthetic bacteria:

• Photosynthetic bacteria are organisms that prepare their food through the process of photosynthesis.
• A photosynthetic bacteria prepares its food by trapping solar radiation with the help of photosynthetic pigments.

Chemosynthetic bacteria:

• Chemosynthetic bacteria are autotrophic bacteria that prepare their food by using chemical energy from a source.
• They do not require light energy like photosynthetic bacteria to prepare their food.

Explanation:

Option 1: Quantasome.

• ​This option is correct.
• Quantasomes are photosynthetic pigments containing granules that are found in the grana of the chloroplasts.
• It contains pigments such as chlorophyll along with carotenoids and other chemical compounds.
• However, photosynthetic bacteria lack chloroplasts. The photosynthetic pigments are scattered in the cytoplasm of a bacterial cell.
• Photosynthetic bacteria like Cyanobacteria use these pigments to carry out photosynthesis.
• Quantasomes are absent in photosynthetic bacteria.

Option 2: PS-I and PS-II.

• This option is incorrect.
• PS-I and PS-II are the pigment systems involved in photosynthesis.
• Oxygenic photosynthetic bacteria like Cyanobacteria have both the PS-I and PS-II.
• PS-II generates a proton motive force for generating ATP. PS-I on the other hand generates electrons.

Option 3: PS-I.

• This option is incorrect.
• PS-I is present in both oxygenic photosynthetic bacteria and anoxygenic photosynthetic bacteria.
• Anoxygenic bacteria like Heliobacteria have only a simplified PS-I system.

Option 4: PS-II.

• This option is incorrect.
• Though PS-II is absent in anoxygenic photosynthetic bacteria like Chlorobi, it is present in oxygenic photosynthetic bacteria.
• Some bacteria like Proteobacteria have only a simplified PS-II system.

So the correct answer is option 1 (Quantasome).

Additional Information 

​Oxygenic photosynthetic bacteria:

• Carry out photosynthesis similar to that seen in plants. Possess both PS-I and PS-II.
• Uses water as a reducing agent and oxygen is released as a by-product during photosynthesis carried out by these bacteria.
• Example: Cyanobacteria

Anoxygenic photosynthetic bacteria:

• Possess only PS-I.
• Uses H₂S and thiosulfate as reducing agents. Oxygen is not released during photosynthesis carried out by these bacteria.
• Example: Chlorobium

The correct answer is Lower as compared to C4 plantsKey Points

• Due to their reduced rate of photorespiration and high rate of photosynthesis, C4 plants are more efficient than C3 plants. 
• So the yield of C3 plants is lower as compared to C4 plants.

Additional Information CAM plants: 

• Any plant that undergoes a form of photosynthesis known as crassulacean acid metabolism, in which carbon dioxide is taken up only at night.
• CAM plants are mostly xerophytic.
• Examples: Orchids, Cacti, Aloe, Pineapple, Agave, Moringa, Some species of Euphorbia and Bromelioideae, etc.

C4 plants:

• ​C4 plants are so called because the first product of CO2 fixation is a C4 organic acid, oxaloacetate, formed by the carboxylation of phosphoenolpyruvate (PEP) by PEP carboxylase.
• The oxaloacetate is converted to other C4 acids (malate or aspartate) and transferred to the bundle sheath.
• Examples of C4 plants include corn, sorghum, sugarcane, millet, and switchgrass.

C3 plants

• These plants use the Calvin cycle in the dark reaction of photosynthesis.
• The leaves of C3 plants do not show Kranz's anatomy.
• Here the photosynthesis process takes place only when the stomata are open.
• Approximately 95% of the shrubs, trees, and plants are C3 plants.

​

Showing C3, CAM and C4 plants

Concept:

Oxidation reaction:

• Oxidation Reaction refers to a reaction in which either the addition of Oxygen takes place or the removal of Hydrogen takes place.
• It can also be said as the process of loss of one or more electrons by atoms or ions.
• Eg - H₂O gets oxidised to release O₂ {Removal of hydrogen}

Reduction Reaction:

• Reduction Reaction refers to a reaction in which either the addition of Hydrogen takes place or the removal of oxygen takes place.
• In the process of reduction, a chemical species also gains electrons.
• It is the reverse of the oxidation reaction.
• Eg - CO₂ gets reduced to form C₆H₁₂O₆ {addition of hydrogen}

Explanation:

• Plants prepare their food by the process called photosynthesis. 
• During photosynthesis, plants trap solar energy or light energy with the help of chloroplast present in the green leaves and convert it into Chemical energy
• A pigment called chlorophyll is present in the chloroplasts which are required in trapping sunlight
• Plants utilize Carbon dioxide and Water for the synthesis of carbohydrates during photosynthesis.
• The CO₂ gets reduced to form the carbohydrates while H₂O (Water) is oxidised and oxygen is liberated as a side product
• This gaseous exchange occurs through the stomata present on the leaf surface

These events can be demonstrated by the following equation:

\(\rm \underset{(Carbon\ dioxide)}{6CO_2} + \underset{(Water)}{6H_2 O} \xrightarrow[Chlorophyll]{Sunlight} \underset{(Carbohydrates)}{C_6H_{12}O_6} + \underset{(Oxygen)}{6O_2}\)

The correct answer is Statement I is true but Statement II is false

Explanation:

Statement I: In C3 plants, some O₂ binds to RuBisCO, hence CO₂ fixation is decreased."

• This statement is true.
• In C3 plants, RuBisCO, the enzyme responsible for fixing CO₂ during the Calvin cycle, can also bind to O₂, leading to a process called photorespiration. Photorespiration competes with the Calvin cycle and reduces the efficiency of CO₂ fixation, thereby decreasing the overall rate of photosynthesis.

Statement II: "In C4 plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration."

• This statement is false.
• In C4 plants, the initial fixation of CO₂ occurs in the mesophyll cells where CO₂ is converted into a four-carbon compound. This compound is then transported to bundle sheath cells where the CO₂ is released and refixed by RuBisCO.
• This spatial separation of initial CO₂ fixation and the Calvin cycle significantly reduces photorespiration in C₄ plants.
• The part of the statement that mesophyll cells show very little photorespiration is technically incorrect because they do not engage in the Calvin cycle where photorespiration occurs. 
• Photorespiration is negligible in C4 plants due to their compartmentalization strategy.

The correct answer is Lycopene 

Explanation:-

• Lycopene is a red-colored carotenoid pigment that gives tomatoes their characteristic red color.
• It is a type of antioxidant pigment that is also found in other red-colored fruits and vegetables, such as watermelon, pink grapefruit, and red bell peppers.
• Lycopene is associated with various health benefits, including antioxidant properties and potential protective effects against certain chronic diseases.

Additional InformationCarotene: Carotene is a type of pigment found in plants, particularly in fruits and vegetables. It is responsible for the yellow, orange, and red colors in many plant tissues. Carotene is a precursor to vitamin A, and it plays a crucial role in photosynthesis and photoprotection in plants. While tomatoes do contain some carotene, particularly beta-carotene, it is not the primary pigment responsible for their red color.

Xanthophylls: Xanthophylls are another type of pigment found in plants, responsible for yellow coloration in various fruits and vegetables. Xanthophylls play a role in photosynthesis and photoprotection, similar to carotenes. 

Phycobilins: Phycobilins are pigments found in certain types of algae, particularly red algae (Rhodophyta), cyanobacteria, and some cryptophytes. Phycobilins play a role in photosynthesis in these organisms, absorbing light energy and transferring it to chlorophyll for photosynthetic processes. 

In summary, while carotene, xanthophylls, and phycobilins are all types of plant pigments, they are not the primary pigment responsible for the red coloration in tomatoes

Conclusion:- Lycopene, a carotenoid pigment, is the predominant pigment in tomatoes, giving them their characteristic red color.

Correct answer is Priestly

Key Points

• The Bell Jar Experiment.
  • J. Priestley (1772) carried out very interesting experiment on Bell jar, rat, pudina or mint and candle. He came to conclude that plants purify air (burning of candles), and gaseous exchange occurs during photosynthesis.
    Priestley observed that a candle burning in a closed space – a bell jar, soon gets extinguished.
  • Similarly, a mouse would soon suffocate in a closed space. He concluded that a burning candle or an animal that breathe the air, both somehow, damage the air. But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn.
  • Priestley hypothesized as follows: Plants restore the air which breathing animals and burning candles remove.
     

Concept:

• Phosphorylation is a process by which a phosphoryl group (PO₃^2-) is added to a molecule.
• Phosphorylation is a vital reaction in biological systems as it aids in cellular storage and the transfer of free energy.
• Photophosphorylation is a type of phosphorylation reaction that takes place in the presence of light during the light reaction of photosynthesis.
• During this process, energy-rich molecules called ATP are produced from ADP by utilizing the energy derived from the transfer of electrons.
•  

 ADP + Pi + Energy \(\rm\xrightarrow[Reaction]{Light}\) ATP 

Explanation:

PHOTOPHOSPHORYLATION:

• Photophosphorylation was discovered in the 1950s by Dr. Arnon and his coworkers in the chloroplasts and bacterial chromatophores.
• It helped in research in the fields such as photosynthesis and bioenergetics.
• Photophosphorylation that occurs during photosynthesis can be summarized as follows:
• During photosynthesis, the transfer of electrons takes place in two ways:

1. Cyclic Photophosphorylation:

• Cyclic electron transfer takes place.
• In this process, only Photosystem I is involved
• During this process, a high-energy electron released from a reaction center (P₇₀₀) returns to the same reaction center.
• Thus the movement of electrons in this process is cyclic.
• Two ATP molecules are produced at the end of cyclic photophosphorylation.

​

2. Non-cyclic Phosphorylation:

• It is a non-cyclic electron transfer process.
• It involves both the photosystems - Photosystem I and Photosystem II.
• In this process, the electrons released from a reaction center do not return to the same reaction center.
• At the end of the process, 1 ATP and 2 NADPH molecules are formed.
• Oxygen is released into the atmosphere by this process.

So from the above-given information, the correct answer is option 1 (Arnon et. al.).

Concept:

Photophosphorylation

• ATP molecules are synthesized by cells (in mitochondria and chloroplast).
• This process of ATP synthesis is called phosphorylation.
• The synthesis of ATP molecules from ADP and inorganic phosphate in the presence of light is called photophosphorylation.

Explanation:

Non-cyclic photophosphorylation

• ​When the two photosystems work in series, PS II followed by PS I, the process is called non-cyclic photophosphorylation.
• Here, photosystems, PS I, and PS II are connected in series by an electron transport chain.
• In this type of process, electrons follow in a non-cyclic manner.
• In PS I, the electrons are transferred to the acceptor molecule, and in presence of an enzyme Ferredoxin- NADP+ reductase, the NADP molecules are reduced to NADPH + H⁺.
• NADP⁺ + 2H⁺ + 2e^- give rise to NADPH + H⁺ .
• In non-cyclic photophosphorylation, in addition to NADPH molecules, ATP molecules are also produced. 

​Cyclic photophosphorylation

• ​When only PS I is present the electrons follow in a cyclic manner. 
• The phosphorylation that occurs due to the cyclic flow of electrons in PS I is called cyclic photophosphorylation.
• In this process, only ATP molecules are formed.

​​​Location for phosphorylation

• Cyclic photophosphorylation occurs in the stroma lamellae.
• Stroma lamellae have only PS I.
• Non-cyclic photophosphorylation occurs in the membrane of grana.
• The grana lamellae have both PS I and PS II.

So, the correct answer is option 1.​

Concept:

• Photosynthesis is the process by which carbohydrates are synthesized from inorganic materials like CO₂ and H2O with the help of light energy which is trapped by pigments like chlorophyll.
• Photosynthetic pigments like chlorophyll are present in the thylakoid region of the chloroplasts.
• Of all the photosynthetic pigments present in a plant, Chlorophyll a is the reaction center that traps the sunlight and converts it into chemical energy.
• Other pigments like chlorophyll b, carotene, and xanthophyll are accessory pigments that trap light energy and transfer it to the reaction center.
• There are two types of reaction centers P₆₈₀ and P₇₀₀ (680 and 700 correspond to the wavelength of light at which maximum absorbance by the chlorophyll molecule is observed. P refers to pigment).
• Thus two pigment systems are involved in photosynthesis. These systems are referred to as Photosystem I and Photosystem II.
• Each photosystem consists of a reaction center and accessory pigments.
• Photosystem I consists of a P₇₀₀ reaction center.
• Photosystem II consists of the P₆₈₀ reaction center.
• PS I takes part in both cyclic and non-cyclic photophosphorylation.
• PS II takes part in only non-cyclic photophosphorylation.

Explanation:

Option 1: Photoionization takes place only in PS I - INCORRECT

• ​Photoionization refers to the phenomenon wherein absorption of a photon by an atom, ion or molecule results in the ejection of an electron from it.
• During photosynthesis, the reaction center of both  PS I and PS II, absorb photons from the sunlight. As a result, a high-energy electron is released from the reaction center.
• Due to this the reaction center becomes unstable.
• Thus photoionization takes place in both PS-I and PS II.

​Option 2: PS II precedes PS I - CORRECT

• ​In photosynthesis, the flow of electrons takes place from PS II to PS I.
• This means that PS II precedes PS I.
• The flow of electrons from PS II to PS I is as follows:
• The flow of electrons is as follows:
• PS II (P680) → Primary electron acceptor → Plastoquinone → Cytochrome b6f complex→ Plastocyanin → PS I (P700)

Option 3: Photolysis of water takes place during PS I - INCORRECT​

• The splitting of a water molecule in the presence of light by green plants is known as the photolysis of water.
• Photolysis of water is part of Photoact II mediated by photosystem II.
• Photosystem II consists of an oxygen-evolving complex (water-splitting complex) where oxidation of water molecules takes place.
• During the photolysis of water, the oxygen molecule is released and hydrogen ions are formed.

Option 4: Cyclic Photophosphorylation involves both PS I and PS II - INCORRECT

• ​It is called so because during cyclic photophosphorylation cyclic electron transfer takes place.
• In this process, only Photosystem I (PS I) is involved
• During this process, a high-energy electron released from a reaction center (P700) returns to the same reaction center.

So the correct answer is option 2 (PS II precedes PS I).