What do we know Questions in English

(B) In bacterial photosynthesis,organisms do not use $H_2O$ as a hydrogen donor. Instead,they typically use $H_2S$ (hydrogen sulphide) as the electron and hydrogen donor. Consequently,they release sulphur or sulphate as a byproduct instead of oxygen.

(D) The correct answer is $D$.
Plants are known as autotrophs because they possess chlorophyll and can synthesize their own organic food material from inorganic substances in the presence of light through the process of photosynthesis.

(C) Carbon is obtained by plants primarily from $CO_2$ present in the atmosphere through the process of photosynthesis.
It is a fundamental element required for the synthesis of carbohydrates,proteins,fats,and nucleic acids.
Therefore,the correct form in which carbon is available to plants is $CO_2$.

(A) Autotrophs are green plants capable of synthesizing their own food from raw materials ($CO_2$,water,and sunlight) through the process of photosynthesis.
Thus,they are independent and self-nourishing organisms.

(B) Marine plants,such as algae and seagrasses,perform photosynthesis to produce organic compounds. These plants derive the necessary $CO_2$ for photosynthesis primarily from the surrounding sea water. In sea water,$CO_2$ exists in equilibrium with bicarbonate ions $(HCO_3^-)$ and carbonate ions $(CO_3^{2-})$,which the plants can utilize as a carbon source.

(B) The correct equation for photosynthesis is $6CO_2 + 12H_2O \xrightarrow{\text{Light, Chlorophyll}} C_6H_{12}O_6 + 6H_2O + 6O_2$.
This equation is more appropriate because it accounts for the $12$ molecules of water consumed in the process,where $6$ molecules of water are released as a byproduct along with $6$ molecules of oxygen $(O_2)$.
This reflects the actual stoichiometry of the light-dependent and light-independent reactions.

(A) Water is an essential raw material for photosynthesis.
It rarely acts as a limiting factor because less than $1\%$ of the total water absorbed by a plant is actually utilized in the process of photosynthesis.
The remaining water is lost through transpiration.

(B) Photosynthesis is an anabolic process in which green plants synthesize organic food (glucose) from inorganic raw materials like $CO_2$ and $H_2O$ in the presence of sunlight and chlorophyll. Therefore,it is essentially a process of manufacturing food. Oxidation of food is a characteristic of respiration,not photosynthesis.

(D) Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.
During this process,plants take in $CO_2$ (carbon dioxide) from the atmosphere through their stomata and release $O_2$ (oxygen) as a byproduct.
Therefore,the gas absorbed during photosynthesis is carbon dioxide.

(B) Photosynthesis is the process by which green plants and some other organisms convert light energy into chemical energy.
This process occurs within specialized organelles called $Chloroplasts$.
Inside the $Chloroplasts$,the light-dependent reactions take place in the thylakoid membranes,where chlorophyll pigments capture light energy to synthesize $ATP$ and $NADPH$,which are forms of chemical energy.

(A) Photosynthesis is a physico-chemical process by which green plants use light energy to drive the synthesis of organic compounds.
In this process,$CO_2$ is reduced to carbohydrates (glucose) using the energy derived from light (photophosphorylation) and the reducing power of $NADPH$.
Option $A$ is correct because the Calvin cycle involves the reduction of $CO_2$ to form sugars.
Option $B$ is incorrect as $NAD^+$ is reduced to $NADH$ in respiration,not photosynthesis.
Option $C$ is a part of the process (photophosphorylation),but the primary definition of photosynthesis is the conversion of light energy into chemical energy stored in carbohydrates.
Option $D$ is a process that occurs in mitochondria during cellular respiration,not in chloroplasts.

(A) solar cooker works by capturing solar energy (light energy) and converting it into heat energy to cook food.
Similarly,in the process of photosynthesis,green plants capture solar energy (light energy) and convert it into chemical energy stored in the form of glucose.
Therefore,the use of a solar cooker is a technological imitation of the natural process of photosynthesis,where solar energy is utilized to perform work or store energy.

(B) During the process of photosynthesis,green plants utilize solar energy to convert carbon dioxide $(CO_2)$ and water $(H_2O)$ into glucose (represented as $(CH_2O)_n$) and release oxygen $(O_2)$ as a byproduct.
The chemical equation for photosynthesis is:
$CO_2 + 2H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light energy}} (CH_2O)_n + H_2O + O_2 \uparrow$
Therefore,plants absorb $CO_2$ and release $O_2$.

(B) Photosynthetically active radiation $(PAR)$ is the spectral range of solar radiation from $400$ to $700 \,nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is essential for the excitation of chlorophyll molecules to initiate the light-dependent reactions.

(A) Green plants are $Autotrophs$ because they have the capacity to manufacture their own food through the process of photosynthesis.
They can fix the radiant energy of the sun into chemical energy stored in organic compounds.

(A) The correct answer is $A$.
Plants obtain carbon primarily from atmospheric $CO_2$ through the process of photosynthesis.
During photosynthesis,plants fix atmospheric $CO_2$ into organic compounds like glucose,which serves as the fundamental source of carbon for their growth and development.

(B) Plants obtain carbon primarily from the atmosphere in the form of $CO_2$ (carbon dioxide) through the process of photosynthesis.
During photosynthesis,plants fix atmospheric $CO_2$ into organic compounds like glucose,which serves as the primary source of carbon for their growth and development.
Therefore,carbon dioxide is the form in which carbon is available to crop plants.

(A) Photosynthetically Active Radiation $(PAR)$ refers to the spectral range of solar radiation from $400$ to $700 \ nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is essential for the excitation of chlorophyll pigments.

(C) Plants absorb a large amount of water through their roots from the soil.
However,only a very small fraction of this absorbed water is utilized in the process of photosynthesis to synthesize organic compounds.
Studies indicate that less than $1\%$ of the total water absorbed by the plant is actually consumed in photosynthesis.
The majority of the water is lost through transpiration.

(A) Photosynthesis is a process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water.
During this process,plants take in $CO_2$ from the atmosphere and release $O_2$ as a byproduct.
The overall chemical equation is: $6CO_2 + 12H_2O \xrightarrow{\text{Light}} C_6H_{12}O_6 + 6O_2 + 6H_2O$.
Therefore,the correct statement is that $CO_2$ is taken in.

(D) Photosynthesis is the process by which green plants synthesize their own food.
The chemical equation for photosynthesis is: $6CO_2 + 12H_2O \xrightarrow{\text{Light, Chlorophyll}} C_6H_{12}O_6 + 6O_2 + 6H_2O$.
In this process,carbon dioxide $(CO_2)$ and water $(H_2O)$ are the essential raw materials (reactants) required for the synthesis of glucose.
Chlorophyll acts as a catalyst/pigment to trap light energy,and glucose is the final product,not a raw material.

(A) Photosynthesis is the process by which green plants convert light energy into chemical energy.
During this process,carbon dioxide and water are used to synthesize glucose $(C_6H_{12}O_6)$,which is a simple sugar.
While plants eventually store this energy in the form of starch,the primary product synthesized directly through the photosynthetic reaction is simple sugar (glucose).

(C) Non-oxygenic photosynthesis is a process where light energy is used to synthesize organic compounds without the production of oxygen as a byproduct.
This process is characteristic of certain groups of bacteria,such as green sulfur bacteria (e.g.,$Chlorobium$) and purple sulfur bacteria (e.g.,$Chromatium$).
Unlike plants,algae,and cyanobacteria,which use $H_2O$ as an electron donor and release $O_2$,these bacteria use other substances like $H_2S$ as an electron donor,resulting in the release of sulfur or other compounds instead of oxygen.
Therefore,bacteria are the organisms that exhibit non-oxygenic photosynthesis.

(C) Photosynthesis is a physico-chemical process by which plants use light energy to synthesize carbohydrates (sugars) from $CO_2$ and water.
In this process,$CO_2$ undergoes reduction to form carbohydrates,which is known as the fixation of $CO_2$.
Therefore,option $C$ provides the most accurate scientific description of the process.

(A) Photosynthetically Active Radiation $(PAR)$ is the spectral range of solar radiation from $400 \ nm$ to $700 \ nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is most effective for driving the light-dependent reactions of photosynthesis.
Therefore,the correct range is $400-700 \ nm$.

(A) The concentration of carbon dioxide $(CO_2)$ in the Earth's atmosphere is approximately $0.03\%$ to $0.04\%$. Among the given options,$0.03\%$ is the standard value typically cited in biology textbooks for the atmospheric concentration of $CO_2$.

(A) Most plants are $Autotrophic$ because they contain chlorophyll and can synthesize their own food through the process of $Photosynthesis$. However,some plants,such as parasitic plants (e.g.,$Cuscuta$) and insectivorous plants,exhibit $Heterotrophic$ nutrition. Therefore,plants as a group exhibit both modes of nutrition.

(A) Photosynthetically Active Radiation $(PAR)$ is the spectral range of solar radiation from $400 \ nm$ to $700 \ nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is essential for the excitation of chlorophyll molecules to initiate the light-dependent reactions of photosynthesis.

(B) Photosynthetically Active Radiation $(PAR)$ refers to the spectral range of solar radiation from $400$ to $700 \ nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is essential for the excitation of chlorophyll pigments.

(A) Photosynthetic microorganisms (such as cyanobacteria and algae) capture solar energy (light energy) and convert it into chemical energy,which is stored in the form of organic compounds like glucose. In biological terms,this stored chemical energy is a form of potential energy. Therefore,the conversion is from solar energy to potential energy.

(B) Autotrophic nutrition is a process where organisms synthesize their own food from simple inorganic substances like $CO_2$ and $H_2O$ using sunlight (photosynthesis) or chemical energy (chemosynthesis).
Plants are the primary examples of autotrophs as they contain chlorophyll and perform photosynthesis.
Fungi are heterotrophic (saprophytic) and obtain nutrients from decaying organic matter.
Animals are heterotrophic (holozoic) and depend on other organisms for food.
Therefore,the correct option is $B$.

(A) Photosynthesis is defined as a $Physico-chemical$ process by which green plants use light energy to drive the synthesis of organic compounds.
It involves the conversion of light energy (physical) into chemical energy (chemical) stored in the bonds of carbohydrates like glucose.
Therefore,it is accurately described as a $Physico-chemical$ process.

(B) Photosynthesis is a physico-chemical process because it involves the conversion of light energy (physical) into chemical energy (chemical) stored in the bonds of organic compounds.
During this process,plants use light energy to synthesize organic compounds (like glucose) from inorganic raw materials ($CO_2$ and $H_2O$).
Therefore,the correct sequence is Physico-chemical and organic.

(B) Photosynthetically Active Radiation $(PAR)$ refers to the spectral range of solar radiation from $400$ to $700 \,nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
This range corresponds to the visible light spectrum,which is essential for the excitation of chlorophyll pigments.

(B) $PAR$ stands for Photosynthetically Active Radiation.
It refers to the spectral range of solar radiation from $400\, nm$ to $700\, nm$ that photosynthetic organisms are able to use in the process of photosynthesis.
Therefore,the correct range is $400\, nm - 700\, nm$.

(N/A) $\Rightarrow$ By the middle of the $19^{th}$ century,the key features of plant photosynthesis were known,specifically that plants could use light energy to synthesize carbohydrates from $CO_{2}$ and water.
$\Rightarrow$ The empirical equation representing the overall process of photosynthesis for oxygen-evolving organisms was understood as:
$\Rightarrow$ $CO_{2} + H_{2}O \xrightarrow{\text{light}} [CH_{2}O] + O_{2}$
$\Rightarrow$ Here,$[CH_{2}O]$ represents a carbohydrate (e.g.,glucose,a six-carbon sugar).

(N/A) - Photosynthesis takes place primarily in the green leaves of plants,but it also occurs in other green parts of the plants (e.g.,$Cactus$).
- The $mesophyll$ cells in the leaves contain a large number of $chloroplasts$.
- Usually,the $chloroplasts$ align themselves along the walls of the $mesophyll$ cells so that they receive the optimum quantity of incident light.

(B) Oxygen was released into the atmosphere primarily through the process of photosynthesis performed by cyanobacteria and later by plants.
The chemical equation for photosynthesis is:
$6CO_{2} + 6H_{2}O \xrightarrow{hv} C_{6}H_{12}O_{6} + 6O_{2} \uparrow$

(A) Plants absorb a large amount of water through their roots. However,only a very small fraction of this water is utilized for metabolic activities. Specifically,approximately $0.2\%$ of the total water absorbed by the plant is used in the process of photosynthesis.

(B) The overall balanced chemical equation for photosynthesis is $6 CO_2 + 12 H_2O \xrightarrow{\text{Light}} C_6H_{12}O_6 + 6 O_2 + 6 H_2O$.
In this process, $6$ molecules of carbon dioxide and $12$ molecules of water are utilized in the presence of light to produce $1$ molecule of glucose, $6$ molecules of oxygen, and $6$ molecules of water.

(D) Photosynthesis is the process by which green plants synthesize glucose $(C_{6}H_{12}O_{6})$ using carbon dioxide $(CO_{2})$ and water $(H_{2}O)$ in the presence of sunlight and chlorophyll.
While the simplified equation is often written as $6CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}$,the most accurate representation accounts for the $12$ molecules of water consumed,resulting in the release of $6$ molecules of oxygen and the regeneration of $6$ molecules of water as a byproduct.
Therefore,the equation $6CO_{2} + 12H_{2}O \xrightarrow{\text{Sunlight, Chlorophyll}} C_{6}H_{12}O_{6} + 6O_{2} + 6H_{2}O$ is the most chemically adequate representation.

(D) Photosynthesis is a physico-chemical process by which green plants use light energy to drive the synthesis of organic compounds.
In this process,plants take in inorganic substances like $CO_2$ (carbon dioxide) and $H_2O$ (water) from the environment.
Using solar energy,these inorganic substances are converted into complex organic compounds like glucose $(C_6H_{12}O_6)$,which serves as food for the plant.

(D) Photosynthesis is the process by which green plants synthesize carbohydrates using carbon dioxide and water in the presence of sunlight and chlorophyll.
The balanced chemical equation for photosynthesis is:
$6CO_2 + 12H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6H_2O + 6O_2$
In this reaction,$6$ molecules of carbon dioxide combine with $12$ molecules of water to produce one molecule of glucose $(C_6H_{12}O_6)$,$6$ molecules of water,and $6$ molecules of oxygen as a byproduct.

(A) Chloroplasts in mesophyll cells are positioned close to the cell wall to maximize the absorption of light for photosynthesis.
By being near the periphery,they reduce the distance light must travel through the cytoplasm,ensuring an optimal amount of light is captured for the light-dependent reactions.
This positioning also helps in the efficient diffusion of $CO_2$ into the chloroplasts,but the primary reason for their peripheral alignment is to optimize light capture.

(B) Photosynthetically Active Radiation $\text{(PAR)}$ refers to the spectral range of solar radiation from $400 \text{ to } 700 \text{ nm}$ that photosynthetic organisms are able to use in the process of photosynthesis.
It is a well-established ecological fact that less than $50 \%$ of the incident solar radiation is photosynthetically active radiation $\text{(PAR)}$.
Furthermore,plants capture only $2-10 \%$ of the $\text{PAR}$ to sustain all life processes in an ecosystem.