All questions of September Week 3 for NEET Exam

Pigments

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

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 .

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.

The sign of ΔG will change from positive to negative (or vice versa) where T = ΔH/ΔS. In cases where ΔG is: negative, the process is spontaneous and may proceed in the forward direction as written. positive, the process is non-spontaneous as written, but it may proceed spontaneously in the reverse direction.

Understanding Satellite Kinetic Energy
When a satellite orbits the Earth, its kinetic energy is determined by its speed and the gravitational pull it experiences. The kinetic energy (KE) of a satellite can be expressed as:
- KE = (1/2) mv^2
Where m is the mass of the satellite and v is its orbital speed.
Effect of Doubling Kinetic Energy
If the kinetic energy of the satellite is doubled:
- New KE = 2 * KE
This implies that the speed of the satellite must increase. Since kinetic energy is proportional to the square of the velocity, to double the kinetic energy, the velocity must be increased by a factor of sqrt(2).
Consequences of Increased Speed
- Increased orbital speed means the satellite will no longer be in a stable orbit. The gravitational force is not enough to keep it in a circular path.
- As a result, the satellite will move into a higher, elliptical trajectory, and eventually escape Earth's gravitational influence.
Options Analysis
Let’s analyze the options provided:
- a) The satellite will escape into space. (Correct)
- b) The satellite will fall down on the Earth. (Incorrect) - Increased speed means it would not fall.
- c) The radius of its orbit will be doubled. (Incorrect) - The orbit will change but not necessarily double.
- d) The radius of its orbit will become half. (Incorrect) - Similar reasoning as above.
Conclusion
Doubling the kinetic energy increases the satellite's speed sufficiently to overcome Earth's gravity, leading it to escape into space. Thus, the correct answer is option 'A'.

Photochemical Phase (Light or Hill Reaction): It occurs inside the thylakoids, especially those of grana region. Photochemical step is dependent upon light.

A spontaneous process is the time-evolution of a system in which it releases free energy and it moves to a lower, more thermodynamically stable energy state. For cases involving an isolated system where no energy is exchanged with the surroundings, spontaneous processes are characterized by an increase in entropy

Extensive Property:

An extensive property is a physical property of a system that depends on the amount of substance present in the system. In other words, extensive properties are additive and scale with the size or amount of the system. The value of an extensive property changes when the size or amount of the system changes.

Explanation:

Out of the given options, the correct answer is option 'B' - Entropy.

Entropy is a measure of the disorder or randomness of a system. It is a thermodynamic property that quantifies the number of microscopic configurations that a system can have. Entropy is an extensive property because it depends on the size or amount of the system.

Comparison with Other Options:

a) Specific Heat Capacity:
Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by a certain amount. It is an intensive property because it does not depend on the amount of substance present. The specific heat capacity of a substance remains the same regardless of the size or amount of the substance.

b) Entropy:
As mentioned earlier, entropy is an extensive property as it depends on the amount of substance present in the system. If the system size or amount changes, the entropy of the system will also change proportionally.

c) Temperature:
Temperature is an intensive property because it does not depend on the amount of substance present. The temperature of a substance remains the same regardless of the size or amount of the substance.

d) Refractive Index:
Refractive index is a measure of how light propagates through a medium. It is an intensive property because it does not depend on the amount of substance present. The refractive index of a substance remains the same regardless of the size or amount of the substance.

Conclusion:

Among the given options, entropy is the only extensive property. It is a thermodynamic property that depends on the amount of substance present in the system. The other options, specific heat capacity, temperature, and refractive index, are intensive properties that do not depend on the amount of substance present.

Something is subjective and can vary depending on individual perspectives and circumstances. It can be determined based on various factors such as usefulness, scarcity, demand, and personal preferences.

The greater the randomness in a system, greater is its entropy. The randomness is greater in liquid state as compared to solid state so the entropy increases when ice melts into water.

Understanding the Problem
Two point masses, 4m and m, are revolving around their common center of mass due to the gravitational force between them. We need to find the ratio of their kinetic energies.
Center of Mass (COM)
- For two point masses, the center of mass can be calculated using the formula:
r_COM = (m1 * r1 + m2 * r2) / (m1 + m2)
- Here, the center of mass will be closer to the larger mass (4m), meaning the distance from the center of mass to mass 4m will be less than the distance to mass m.
Distance from the Center of Mass
- Let the distance from the center of mass to mass 4m be r1 and to mass m be r2.
- Since the masses are 4m and m, we have:
r1 = (m / (4m + m)) * d = (1/5)d
r2 = (4m / (4m + m)) * d = (4/5)d
Kinetic Energy (KE) Formula
- The kinetic energy of a mass in circular motion is given by:
KE = (1/2)mv^2
- For the two masses, we can express their kinetic energies as:
KE_1 (for mass 4m) = (1/2)(4m)(v1^2)
KE_2 (for mass m) = (1/2)(m)(v2^2)
Velocity Relationship
- For two bodies in circular motion about a common center, the ratio of their velocities is inversely proportional to the ratio of their distances from the center of mass:
v1 / v2 = r2 / r1 = (4/5) / (1/5) = 4
Calculating the Ratio of Kinetic Energies
- Substituting the velocity relationship, we find:
KE_1 : KE_2 = (4)(4m) : (1)(m) = 16m : m = 16 : 1
- However, since we are looking for kinetic energy per unit mass, we can simplify further:
The ratio becomes 1 : 4.
Conclusion
Thus, the correct answer is option 'A': the ratio of their kinetic energies is 1 : 4.

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.

Explanation:

The concept of entropy:
Entropy is a thermodynamic property that measures the degree of disorder or randomness in a system. It is denoted by the symbol 'S'. The entropy of a substance increases with an increase in its disorder.

Evaporation of water:
Evaporation is the process by which water molecules in a liquid state gain enough energy to become vapor or gas molecules. It occurs at the surface of the liquid and is a phase transition from the liquid phase to the gas phase.

Entropy change during evaporation:
During evaporation, water molecules at the surface of the liquid gain energy from the surroundings and overcome the intermolecular forces holding them together. They then escape into the gas phase, resulting in the conversion of liquid water into water vapor.

1. Disorder of the system: The liquid state of water has a higher degree of order as compared to the gaseous state. In the liquid phase, water molecules are closely packed and have a regular arrangement, while in the gaseous phase, the molecules are randomly distributed and move freely.
2. Entropy change: As water evaporates, the disorder of the system increases. The liquid water molecules are confined to a limited space and have restricted movement, while the water vapor molecules have greater freedom and random motion. This increase in disorder leads to an increase in entropy.

Conclusion:
Therefore, during the evaporation of water, the entropy increases. Option 'B' is the correct answer.

Hg(l) is the chemical formula for liquid mercury.

Explanation:

Statement a: Photochemical phase occurs inside the thylakoids, especially those of the grana region.
- The thylakoids are membrane-bound compartments inside the chloroplast where the light-dependent reactions of photosynthesis occur.
- The grana are stacks of thylakoids where the chlorophyll molecules are located, allowing for the absorption of light energy.

Statement b: Biosynthetic phase reactions occur in the stroma or matrix of chloroplasts and are dependent upon light.
- The biosynthetic phase, also known as the Calvin cycle or light-independent reactions, takes place in the stroma of the chloroplast.
- During this phase, energy from the light-dependent reactions is used to convert carbon dioxide into glucose through a series of enzymatic reactions.

Conclusion:
- Both statements are partially correct. Statement a is true as the photochemical phase indeed occurs inside the thylakoids, particularly in the grana region. However, statement b is false as the biosynthetic phase reactions occur in the stroma, not dependent upon light.

Understanding Gravitational Acceleration
Gravitational acceleration at the surface of the Earth (g) is approximately 9.81 m/s². As you move away from the Earth's surface, gravitational acceleration decreases according to the formula:
g' = g / (1 + h/R)²
Where:
- g' is the gravitational acceleration at height h,
- g is the gravitational acceleration at the surface (9.81 m/s²),
- R is the radius of the Earth (approximately 6400 km),
- h is the height above the surface.
Condition for One Fourth of Surface Gravity
To find the height where gravitational acceleration is one fourth of that at the surface, we set up the equation:
g' = g/4
Substituting the formula:
g / (1 + h/R)² = g/4
This simplifies to:
1 / (1 + h/R)² = 1/4
Taking the square root of both sides gives:
1/(1 + h/R) = 1/2
From this, we can derive:
1 + h/R = 2
This leads to:
h/R = 2 - 1
Thus,
h/R = 1
h = R
Conclusion: Height Above Earth's Surface
The height at which gravitational acceleration is one fourth of that at the Earth's surface is equal to the radius of the Earth (R). Therefore, the correct answer is:
Option D: Re

A state function is the property of the system whose value depends only on the initial and final state of the system and is independent of the path. It is a state function because it is independent of the path. Heat (q) and work (W) are not state functions being path dependent.

¥¥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.