All questions of Photosynthesis in Higher Plants for NEET Exam

Pigments

C is correct

6(CO2) + 12(H2O) ----------> C6H12O6 +6(O2) + 6H2O
In photosynthesis phototrophs synthesize glucose and water and evolve O2 as by product

H2O and NADP is reduced

Mitochondria and chloroplasts

In PS-I, the reaction centre chlorophyll a has an absorption peak at 700 nm, hence, is called P 700 while in PS-H, it has absorption maxima at 680 nm, so is called P 680.
so the correct answer is b) 700nm

The energy from the sun, raises an energy level in the chlorophyll molecule, causing electrons to leave the molecule and travel along the electron transport chain (ETC) in a series of oxidation and reductions. In doing so it releases energy converting ADP+Pi into ATP. Photolysis (splitting of water) occurs, and the electrons produced, replace those lost. This is the Light Dependant stage as it relies on light energy

Solarisation is the process of destruction of chlorophyll due to prolonged exposure to sunlight. This phenomenon is commonly observed in plants that grow in areas with high solar radiation. Here is a detailed explanation of the process:

Explanation:
Chlorophyll is the green pigment present in the leaves of plants. It plays a crucial role in photosynthesis, which is the process by which plants convert sunlight into energy. However, prolonged exposure to sunlight can damage the chlorophyll molecules, leading to their destruction. This process is known as solarisation.

Solarisation occurs due to the following reasons:

1. High intensity of sunlight: Plants that grow in areas with high solar radiation are more prone to solarisation. This is because the intensity of sunlight in these areas is much higher than in other regions.

2. Extended exposure to sunlight: The longer a plant is exposed to sunlight, the greater the damage to its chlorophyll molecules. This is why solarisation is more common during the summer months, when the days are longer and the sun is more intense.

Effects of solarisation:

1. Reduced photosynthesis: Solarisation damages the chlorophyll molecules, which reduces the plant's ability to carry out photosynthesis. This can lead to stunted growth and reduced yield.

2. Loss of colour: As the chlorophyll molecules are destroyed, the leaves of the plant lose their green colour and turn yellow or brown.

3. Increased susceptibility to pests and diseases: Plants that have been solarised are more susceptible to pests and diseases, as their weakened state makes them more vulnerable to attack.

Prevention of solarisation:

1. Shade: Providing shade to the plants can reduce their exposure to sunlight and prevent solarisation. This can be done by using shade cloth or by planting the crops under trees.

2. Watering: Regular watering can help cool down the plants and reduce the damage caused by solarisation.

3. Timely harvesting: Harvesting the crops before they are fully mature can reduce their exposure to sunlight and prevent solarisation.

In conclusion, solarisation is the process of destruction of chlorophyll due to prolonged exposure to sunlight. It can have a negative impact on plant growth and yield, and can be prevented by providing shade, regular watering, and timely harvesting.

Photorespiration is a wastefull process because it doesn't synthesis ATP.
but in new ncert it is mentioned that the requirements of photorespiration is not known yet.

##ncert refer kro yrr... directly Diya hua h..

The principal metabolic feature of CAM plants is assimilation of CO2 at night into malic acid which is stored in the vacuole. Malate is generated in the reaction catalyzed by PEP carboxylase and PEP is, in turn, generated by degradation of starch or soluble sugars. During the day, malate is released from the vacuole and is decarboxylated to provide CO2 for fixation in the Benson–Calvin cycle behind closed stomata. Starch and sugars are then resynthesized .

Only ATP is formed

Phosphorylation: A biochemical process that involves the addition of phosphate to an organic compound. Examples include the addition of phosphate to glucose to produce glucose monophosphate and the addition of phosphate to adenosine diphosphate (ADP) to form adenosine triphosphate (ATP). Phosphorylation is carried out through the action of enzymes known as phosphotransferases or kinases.

Photosynthesis and CO2 fixation

Photosynthesis is a process by which plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into organic compounds and oxygen. This process is essential for life on earth as it produces the oxygen that we breathe and provides food for organisms that cannot produce their own.

CO2 fixation is the process by which carbon dioxide is transformed into an organic molecule that can be used by living organisms. This process is important because carbon dioxide is an essential component of the atmosphere, but it is not readily available to most organisms in its gaseous form.

PGA as the first CO2 fixation product

PGA (phosphoglyceric acid) is the first stable product of CO2 fixation in photosynthesis. It is formed when carbon dioxide combines with a five-carbon sugar called ribulose bisphosphate (RuBP) in a reaction catalyzed by the enzyme Rubisco (ribulose bisphosphate carboxylase/oxygenase).

Discovery of PGA

The discovery of PGA as the first CO2 fixation product was made by Melvin Calvin and his colleagues in the 1940s. They used radioactive carbon-14 to trace the movement of carbon through the photosynthetic process and discovered that PGA was the first stable product of CO2 fixation.

Source of PGA

PGA is produced in the stroma of the chloroplasts in plant cells. It is then used to make glucose and other organic compounds through a series of enzyme-catalyzed reactions known as the Calvin cycle.

Role of algae in PGA discovery

Algae played a crucial role in the discovery of PGA as the first CO2 fixation product. Algae are photosynthetic organisms that are capable of fixing carbon dioxide in a similar way to plants. They were used by Calvin and his colleagues as a model system to study photosynthesis and CO2 fixation.

Conclusion

In conclusion, PGA was discovered as the first CO2 fixation product in photosynthesis by Melvin Calvin and his colleagues in the 1940s. This discovery was made using algae as a model system and has since been confirmed in plants and other photosynthetic organisms.

Carbon dioxide fixation takes place in absence of sunlight. Dark reaction make use of these organic energy molecules ATP and NADPH. This reaction cycle is also called as Calvin benison cycle. It occurs in the stroma. It requires to fix carbon dioxide into carbohydrates.
So option " A " is correct answer.

Chlorophyll, any member of the most important class of pigments involved in photosynthesis, the process by which light energy is converted to chemical energy through the synthesis of organic compounds. Chlorophyll is found in virtually all photosynthetic organisms, including green plants, prokaryotic blue-green algae (cyanobacteria), and eukaryotic algae. It absorbs energy from light; this energy is then used to convert carbon dioxide to carbohydrates.

Splitting of water in photosynthesis is called photolysis of water or lysis of water molecules which occur by the action of light . In this the water molecules breaks and form hydrogen and oxygen .
H2O-----> 2H+ +2e- + 1/2O2

Most eukaryotic cells have mitochondria, which produce ATP from products of the citric acid cycle, fatty acid oxidation, and amino acid oxidation. At the mitochondrial inner membrane, electrons from NADH and FADH2 pass through the electron transport chain to oxygen, which is reduced to water.

Photochemical phase or Light reaction

The light reaction is the first stage of photosynthesis that occurs in the thylakoid membrane of the chloroplast. It requires light energy to break down water molecules into oxygen and hydrogen ions. The hydrogen ions are used to generate ATP and NADPH, which are used in the second stage of photosynthesis, the dark reaction.

Process of Light Reaction:

1. Absorption of Light Energy: Chlorophyll pigments present in the thylakoid membrane absorb light energy and transfer it to the reaction center.

2. Generation of ATP: The absorbed light energy is used to generate ATP by the process of photophosphorylation.

3. Generation of NADPH: The absorbed light energy is also used to generate NADPH by the process of photoreduction.

4. Splitting of Water Molecules: Water molecules are split into oxygen and hydrogen ions by the process of photolysis.

5. Release of Oxygen: The oxygen produced by the photolysis of water is released into the atmosphere.

Importance of Light Reaction:

1. Production of ATP and NADPH: The light reaction produces ATP and NADPH, which are used in the dark reaction to synthesize glucose.

2. Release of Oxygen: The oxygen produced by the light reaction is released into the atmosphere, which is essential for the survival of living organisms.

3. Maintenance of Chloroplast: The light reaction helps in the maintenance of chloroplast by generating ATP, which is used to power various metabolic processes in the chloroplast.

Conclusion:

The light reaction is a critical process in photosynthesis that generates ATP and NADPH, which are used in the dark reaction to synthesize glucose. It also releases oxygen into the atmosphere, which is essential for life on earth.

Maize (option B) has Kranz anatomy.

Explanation:
Maize, also known as corn, is a C4 plant that exhibits a specialized leaf anatomy called Kranz anatomy. Kranz anatomy is characterized by the presence of two distinct types of photosynthetic cells: bundle sheath cells and mesophyll cells.

Bundle sheath cells:
- In maize, the bundle sheath cells are arranged in a ring-like manner around the vascular bundles.
- They are tightly packed and contain numerous chloroplasts.
- The walls of bundle sheath cells are thickened and contain many plasmodesmata, which allow for the exchange of metabolites between cells.
- The bundle sheath cells are responsible for the initial fixation of carbon dioxide (CO2) during photosynthesis.

Mesophyll cells:
- The mesophyll cells of maize leaves surround the bundle sheath cells.
- They are loosely arranged and contain fewer chloroplasts compared to bundle sheath cells.
- The mesophyll cells are involved in the initial uptake of carbon dioxide from the atmosphere.

Kranz anatomy and C4 photosynthesis:
- Kranz anatomy is a structural adaptation that enhances the efficiency of C4 photosynthesis.
- C4 photosynthesis is a biochemical pathway that helps plants overcome the limitations of the traditional C3 pathway, especially under high light and high temperature conditions.
- In C4 plants like maize, carbon dioxide is initially fixed into a four-carbon compound in the mesophyll cells, thanks to the enzyme phosphoenolpyruvate carboxylase (PEP carboxylase).
- The four-carbon compound is then transported to the bundle sheath cells, where it is decarboxylated to release CO2.
- The CO2 released in the bundle sheath cells is then used in the Calvin cycle for the synthesis of sugars.
- This spatial separation of initial CO2 fixation and the Calvin cycle helps reduce photorespiration and increases the efficiency of carbon fixation.

Conclusion:
In conclusion, maize (option B) exhibits Kranz anatomy, which is a specialized leaf anatomy found in C4 plants. This anatomical adaptation enhances the efficiency of C4 photosynthesis, allowing maize to thrive in environments with high light and temperature conditions.

As it gives hydrogen n reduce other components so it is called reducing power..

The Light Reaction of Photosynthesis
The light reaction is the first stage of photosynthesis, occurring in the thylakoid membranes of chloroplasts. Its primary function is to convert light energy into chemical energy.
Key Products of the Light Reaction
- ATP (Adenosine Triphosphate):
- Acts as an energy currency in the cell.
- Generated through photophosphorylation during the light-dependent reactions.
- NADPH2 (Nicotinamide Adenine Dinucleotide Phosphate):
- Serves as a reducing agent in the Calvin cycle.
- Produced by the reduction of NADP+ using electrons derived from water splitting.
- Oxygen (O2):
- Released as a byproduct during the photolysis of water.
- While essential for aerobic respiration, it is not the ultimate gain.
Overall Importance of ATP and NADPH2
- Both ATP and NADPH2 are crucial for the subsequent phase of photosynthesis, the Calvin cycle.
- They provide the necessary energy and reducing power for the synthesis of glucose from carbon dioxide.
Conclusion
Thus, the ultimate gain of the light reaction is both ATP and NADPH2, making option 'A' the correct answer. These products are indispensable for fueling the processes of life, particularly in photosynthetic organisms.

Explanation:
Algae and other submerged plants exhibit a phenomenon called diurnal vertical migration, where they rise to the surface of the water during the day and sink to the bottom at night. The correct answer to why this occurs is option 'c', which states that they become buoyant due to the accumulation of oxygen (O2) as a result of photosynthesis.

Photosynthesis and Oxygen Production:
During daylight hours, algae and other submerged plants conduct photosynthesis, a process in which they use sunlight, carbon dioxide (CO2), and water (H2O) to produce glucose (food) and oxygen (O2). This process occurs in specialized organelles called chloroplasts, which contain the pigment chlorophyll.

Accumulation of Oxygen:
As these plants photosynthesize, they release oxygen into the surrounding water. The oxygen produced is then dissolved in the water, causing an increase in oxygen concentration. This accumulation of oxygen in the water leads to the plants becoming buoyant, making them rise to the surface.

Role of Oxygen in Buoyancy:
The accumulation of oxygen in the water reduces its density, making it less dense than the plants themselves. As a result, the plants experience a net upward force, causing them to float or remain suspended near the water's surface. This buoyancy enables them to maximize their exposure to sunlight, which is essential for photosynthesis.

Sinking at Night:
At night, when there is no sunlight available for photosynthesis, the plants cease their oxygen production. As a result, the oxygen concentration in the water decreases, and the water becomes denser. This increase in density causes the plants to lose their buoyancy and sink down to the bottom of the water body.

Significance of Diurnal Vertical Migration:
The diurnal vertical migration exhibited by algae and other submerged plants serves several purposes. By rising to the surface during the day, they can access sunlight for photosynthesis, ensuring the production of food and energy. Additionally, being near the surface allows them to disperse their offspring or spores effectively. Sinking to the bottom at night provides protection from herbivores and other potential threats present near the surface.

In conclusion, algae and other submerged plants rise to the surface of the water during the day and sink at night due to the accumulation and reduction of oxygen, respectively. This diurnal vertical migration enables them to optimize their photosynthesis, reproductive strategies, and protection in their aquatic environment.

Both respiration and photosynthesis involve electron transfer across a series of electron carriers embedded in the inner mitochondrial membrane and the thylakoid membrane respectively. Cytochromes are responsible for ATP production through electron transport and are iron containing proteins. They catalyze redox reaction and the heme group interconverts between oxidation states Fe2+ (reduced) and Fe3+ (oxidized) states.

¥¥In 1905, Blackman gave the Law of Limiting factors. When several factors affect any biochemical process, then this law comes into effect. This states that:

If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value. It is the factor which directly affects the process if this quantity is changed.

•Blackman's law of limiting factors determines the rate of the photosynthesis.

It is named after a scientist Hatch and slack pathway. basically this pathway helps plant to minimise water loss.. as we know that photosynthesis takes place in mesophyll cell but in this c4 pathway photosynthesis occurs in mesophyll as well as bundle sheath cell. mainly glucose molecule will form in bundle sheat cell.