Mix Examples- Photosynthesis in Higher Plants Questions in English

(C) Photosynthesis is a process that utilizes light energy to convert carbon dioxide and water into glucose and oxygen.
This process is driven by the absorption of light by photosynthetic pigments,primarily chlorophyll.
These pigments are capable of absorbing light within the visible spectrum ($380 \ nm$ to $750 \ nm$),regardless of the source of that light.
Therefore,photosynthesis can occur in sunlight or any artificial light source that provides wavelengths within the visible range.

(B) During daylight hours,the rate of photosynthesis is significantly higher than the rate of respiration.
In active plants,the rate of photosynthesis is typically about $8$ to $10$ times higher than the rate of respiration.
Since the stoichiometry of photosynthesis produces $O_2$ in proportion to $CO_2$ fixation,and respiration consumes $O_2$ in proportion to $CO_2$ release,the ratio of oxygen produced to oxygen consumed is approximately $10:1$ under optimal conditions.

(D) The compensation point in an ecosystem is reached when the rate of photosynthesis equals the rate of respiration. In a closed aquarium system,if the $CO_2$ produced by the respiration of both animals and plants is exactly balanced by the $CO_2$ consumed during photosynthesis by the plants,the system reaches a steady state. Under constant illumination,if this balance is maintained,the net exchange of gases with the environment becomes zero,effectively creating an infinite compensation period where the system remains self-sustaining.

(C) The Emerson enhancement effect describes the phenomenon where the rate of photosynthesis in the presence of both red and far-red (or different wavelengths) light is greater than the sum of the rates when each wavelength is provided individually.
In this scenario, the yield in blue light is $10$ units and in red light is $40$ units.
If the effect is synergistic, the combined yield must be greater than the simple sum of the individual yields ($10 + 40 = 50$ units).
Therefore, the yield must be greater than $50$ units.
Among the given options, $60$ units is the only value greater than $50$ units, indicating a synergistic effect.

(D) Photosynthesis is a process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.
It involves the conversion of light energy into chemical energy.
Since it involves the synthesis of complex organic compounds (glucose) from simple inorganic substances ($CO_2$ and $H_2O$) using light energy,it is defined as a biological photometabolism process.

(B) The correct answer is $B$.
Normally,plants utilize sunlight for the process of photosynthesis.
However,certain marine algae are adapted to perform photosynthesis even under low-intensity light conditions,such as moonlight.
Additionally,photosynthesis can also occur under artificial light sources like electric light,provided the light intensity and wavelength are sufficient for the chlorophyll pigments to absorb energy.

(B) Photosynthesis is a process in which $CO_2$ is reduced to carbohydrates,making it a reductive process.
It requires energy in the form of light,making it an endergonic process.
It involves the synthesis of complex organic molecules from simpler inorganic substances,making it an anabolic process.
Therefore,photosynthesis is reductive,endergonic,and anabolic.

(A) In the process of photosynthesis,plants capture solar energy and convert it into chemical energy stored in the bonds of organic compounds (glucose).
Scientific studies indicate that the efficiency of this conversion process is relatively low.
Specifically,only about $1\%$ to $2\%$ of the total incident solar radiation is converted into chemical energy by plants.
This energy is stored as potential energy within the chemical bonds of the synthesized carbohydrates.
Therefore,the correct range for the conversion of radiant energy into potential energy in plants is $1-2\%$.

(C) Hill's reaction refers to the light-dependent reactions of photosynthesis,which occur in the thylakoid membranes.
The primary products of the light reaction are $ATP$ and $NADPH_2$ (or $NADPH$),which are chemical energy carriers.
Blackman's reaction refers to the light-independent reactions (Calvin cycle) of photosynthesis,which occur in the stroma.
These reactions utilize the $ATP$ and $NADPH_2$ produced during the light reaction to fix carbon dioxide into glucose.
Therefore,the correct products used are $ATP$ and $NADPH_2$.

(B) Respiration is a metabolic process that releases $CO_2$ into the atmosphere as a byproduct. However,the concentration of $CO_2$ in the atmosphere remains relatively stable due to the process of photosynthesis. During photosynthesis,autotrophic organisms like plants,algae,and cyanobacteria consume $CO_2$ from the atmosphere to synthesize glucose $(C_6H_{12}O_6)$ using solar energy. This continuous cycle of $CO_2$ release through respiration and $CO_2$ consumption through photosynthesis maintains the balance of $CO_2$ in the biosphere.

(C) Glucose is synthesized during the process of photosynthesis in plants.
During photosynthesis,plants capture solar energy (light energy) and convert it into chemical energy stored in the bonds of glucose molecules.
Therefore,the ultimate source of the energy stored in glucose is the Sun.

(C) Although $CO_2$ is continuously released into the atmosphere through the process of respiration by living organisms,its concentration remains relatively constant due to the process of photosynthesis. During photosynthesis,green plants and other autotrophs absorb $CO_2$ from the atmosphere and convert it into carbohydrates (glucose) using solar energy. This process acts as a major carbon sink,balancing the $CO_2$ released by respiration and maintaining the atmospheric equilibrium.

(D) In submerged hydrophytes (plants that remain completely submerged in water),the stomata are absent. These plants absorb $CO_2$ directly through their general body surface (epidermis). In an aquatic environment,$CO_2$ exists in equilibrium as dissolved $CO_2$,carbonates,and bicarbonates. Submerged plants can utilize these forms for photosynthesis. Therefore,the correct answer is $(d)$.

(A) Oxidative phosphorylation occurs in the mitochondria during cellular respiration,while photophosphorylation occurs in the chloroplasts during photosynthesis.
Both processes involve an electron transport chain $(ETC)$ where electrons are transferred through a series of membrane-bound protein complexes.
Cytochromes are iron-containing hemoproteins that act as essential electron carriers in both the mitochondrial $ETC$ and the photosynthetic $ETC$.
Therefore,cytochromes are common to both processes.

(A) Green plants perform photosynthesis in the presence of light,which releases $O_2$ as a byproduct into the water.
Fishes require this dissolved $O_2$ for their respiration.
Therefore,the presence of green plants ensures a continuous supply of oxygen,allowing the fishes to thrive better.

(C) Light plays a crucial role in many plant processes.
$1$. Seed germination is often regulated by light (photoblasty).
$2$. Flowering is controlled by photoperiodism.
$3$. Food manufacture (photosynthesis) is directly dependent on light.
$4$. Osmosis is a physical process involving the movement of water across a semi-permeable membrane,and fertilization is the fusion of gametes; neither of these processes is directly regulated or affected by light.

(B) Photosynthesis is the most vital process for the existence of life on Earth.
It is the primary source of organic food for almost all living organisms.
It is also the only biological process that releases $O_2$ into the atmosphere,which is essential for the respiration of aerobic organisms.

(D) The energy from the sun reaches the Earth in the form of electromagnetic radiation,specifically as $photons$ (light particles).
These $photons$ are captured by $electrons$ in the chlorophyll pigments of plants during the process of photosynthesis.
Therefore,the correct sequence is $photons$ and $electrons$.

(A) The term 'Sun basket' is metaphorically used for green plants.
Green plants are called 'Sun baskets' because they capture solar energy and convert it into chemical energy (food) through the process of photosynthesis.
This stored energy serves as the primary source of energy for almost all living organisms on Earth.

(B) Photosynthesis is a process in which $CO_2$ is reduced to carbohydrates,making it a reductive process.
It requires energy in the form of light,making it an endothermic process.
It involves the synthesis of complex organic molecules from simpler inorganic substances,making it an anabolic process.
Therefore,photosynthesis is a reductive,endothermic,anabolic process.

(D) Photosynthetic bacteria differ from green plants in several fundamental ways:
$1$. Pigments: Bacteria contain bacteriochlorophyll,which differs from the chlorophyll $a$ and $b$ found in green plants.
$2$. Electron Donor: Green plants use $H_2O$ as an electron donor,which results in the release of $O_2$. In contrast,photosynthetic bacteria (like purple and green sulfur bacteria) use substances like $H_2S$ or organic compounds as electron donors,not $H_2O$.
$3$. Oxygenic vs Non-oxygenic: Because they do not use $H_2O$ as an electron donor,the photosynthetic process in these bacteria does not produce $O_2$,making it non-oxygenic,whereas green plants perform oxygenic photosynthesis.
Therefore,all the given options are correct.

(C) In the $C_3$ cycle (Calvin cycle),the synthesis of one molecule of glucose $(C_6H_{12}O_6)$ requires $18$ $ATP$ and $12$ $NADPH_2$ molecules.
In the $C_4$ cycle (Hatch-Slack pathway),the synthesis of one molecule of glucose requires $30$ $ATP$ and $12$ $NADPH_2$ molecules.
Therefore,for $C_3$ and $C_4$ pathways respectively,the $ATP$ requirements are $18$ and $30$ molecules.

(B) Photosynthesis is a vital biological process that sustains life on Earth.
$1$. It synthesizes glucose,which serves as the primary energy source for almost all consumers in the food chain.
$2$. It releases $O_2$ as a byproduct,which is essential for the cellular respiration of aerobic organisms.
$3$. This released $O_2$ also contributes to the formation of the ozone layer $(O_3)$,which protects the Earth from harmful $UV$ radiation.
$4$. Increasing the greenhouse effect is a negative environmental impact caused by the accumulation of greenhouse gases like $CO_2$,not a utility of photosynthesis. In fact,photosynthesis helps mitigate the greenhouse effect by consuming $CO_2$.

(C) Photosynthesis is the biological process by which green plants,algae,and some bacteria convert light energy from the sun into chemical energy stored in the bonds of glucose molecules.
In this process,carbon dioxide and water are converted into glucose and oxygen using chlorophyll as a pigment to capture light energy.
Respiration,digestion,and fermentation are processes that primarily involve the breakdown of organic molecules to release energy,rather than the conversion of light energy into chemical energy.

(C) Photo-oxidation of chlorophyll is the process where chlorophyll molecules are destroyed by high-intensity light in the presence of oxygen. This phenomenon is known as $Solarization$. It typically occurs when plants are exposed to excessive light,leading to the bleaching of chlorophyll pigments.

(B) Photosynthesis is the unique process that provides the basis for life on Earth.
It is the primary source of all food on Earth and is also responsible for the release of oxygen into the atmosphere by green plants.
Through this process,solar energy is converted into chemical energy,which sustains almost all living organisms.

(C) Photosynthesis is the biological process by which green plants and some other organisms convert light energy into chemical energy.
During this process,plants take in $CO_2$ from the atmosphere and release $O_2$ as a byproduct.
The overall chemical equation for photosynthesis is: $6CO_2 + 12H_2O \xrightarrow{\text{Light}} C_6H_{12}O_6 + 6O_2 + 6H_2O$.

(A) The correct answer is $A$.
$C_3$ plants are those that perform the Calvin cycle directly,such as wheat,rice,and soybeans.
Maize is a $C_4$ plant,not a $C_3$ plant.
$PGA$ (Phosphoglyceric acid) is the first stable product of the Calvin cycle.
$C_4$ plants follow the Hatch-Slack cycle (e.g.,Sorghum,Maize,Sugarcane).
$C_4$ plants are characterized by the presence of Kranz anatomy in their leaves.

(B) RuBisCO (Ribulose$-1,5-$bisphosphate carboxylase-oxygenase) is the most abundant protein on Earth.
It is a key enzyme in the Calvin cycle,responsible for the fixation of atmospheric $CO_2$ in plants during photosynthesis.
Because it is essential for carbon fixation in all photosynthetic organisms,it is found in massive quantities in the chloroplasts of green plants.

(B) Photosynthetic bacteria generally contain only one type of photosystem ($PS-I$ or $PS-II$) and perform anoxygenic photosynthesis.
However,$Cyanobacteria$ are unique among prokaryotes because they perform oxygenic photosynthesis,similar to higher plants.
They possess both $PS-I$ and $PS-II$ systems,which allow them to split water molecules to release oxygen as a byproduct.
Therefore,the correct option is $B$.

(B) Photosynthesis is an anabolic,endergonic,and redox process.
In photosynthesis,$H_2O$ is oxidized to $O_2$,and $CO_2$ is reduced to glucose $(C_6H_{12}O_6)$.
It is an endergonic process because it requires energy in the form of light,not an exothermic reaction.
It acts as a bridge between the biotic (living) and abiotic (non-living) worlds by converting solar energy into chemical energy,which sustains life on Earth.
Option $A$ is incorrect because it reverses the oxidation and reduction roles.
Option $C$ is incorrect because photosynthesis is endergonic,not exothermic.
Therefore,option $B$ is the most accurate description among the choices provided.

(C) During the day,submerged plants perform photosynthesis.
As a result of photosynthesis,$O_2$ is produced as a byproduct.
These $O_2$ bubbles get trapped in the plant body or on the surface of the leaves,which increases the buoyancy of the plant,causing it to float on the water surface.
At night,photosynthesis stops,and the $O_2$ bubbles are either consumed in respiration or escape into the water,causing the plant to lose its buoyancy and sink to the bottom.

(C) The green parts of plants contain chlorophyll,a pigment that captures light energy. This energy is utilized to convert carbon dioxide and water into glucose and oxygen,a process known as photosynthesis. Therefore,the green parts are primarily involved in photosynthesis.

(B) During the process of photosynthesis,plants capture light energy and convert it into chemical energy.
This chemical energy is stored in the form of organic compounds,specifically carbohydrates (glucose/starch),which are referred to as stored food.
$NADP$ is a coenzyme involved in electron transport,while $DNA$ and $RNA$ are nucleic acids involved in genetic information storage and protein synthesis,not energy storage.

(B) Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.
In eukaryotic cells,this process takes place within specialized organelles called $Chloroplasts$.
$Chloroplasts$ contain the pigment chlorophyll,which captures light energy to drive the synthesis of glucose from carbon dioxide and water.

(C) In the Calvin cycle ($C_3$ cycle),the first stable product formed after the fixation of $CO_2$ is $3$-phosphoglyceric acid $(3-PGA)$,which is a $3$-carbon compound.
In the Hatch-Slack cycle ($C_4$ cycle),the first stable product formed after the fixation of $CO_2$ is oxaloacetic acid $(OAA)$,which is a $4$-carbon compound.
Therefore,the first stable products are $3-C$ and $4-C$ compounds respectively.

(B) Photosynthesis is a redox reaction.
In this process,$CO_2$ is reduced to form carbohydrates (glucose),while water $(H_2O)$ is oxidized to release oxygen $(O_2)$.
The overall chemical equation is: $6CO_2 + 12H_2O \xrightarrow{\text{Light}} C_6H_{12}O_6 + 6H_2O + 6O_2$.
Thus,$CO_2$ gains electrons (reduction) and $H_2O$ loses electrons (oxidation).

(B) In photosynthesis,the light-dependent reaction (light reaction) occurs in the thylakoid membranes of the chloroplast,where solar energy is converted into chemical energy in the form of $ATP$ and $NADPH$. These energy carriers are then utilized in the light-independent reaction (dark reaction or Calvin cycle),which takes place in the stroma of the chloroplast,to fix $CO_2$ into carbohydrates. Therefore,$ATP$ acts as an energy shuttle transferring energy from the light reaction to the dark reaction.

(D) Statement $(A)$ is incorrect because the $Z$-scheme involves both $PS-II$ and $PSI$.
Statement $(B)$ is correct because cyclic photophosphorylation involves only $PSI$ where electrons circulate back to the reaction center.
Statement $(C)$ is incorrect because cyclic photophosphorylation produces only $ATP$,not $NADPH_2$. $NADPH_2$ is produced in non-cyclic photophosphorylation.
Statement $(D)$ is correct because the stroma lamellae membranes lack $PS-II$ as well as the enzyme $NADP$ reductase $(FNR)$.
Therefore,statements $(B)$ and $(D)$ are correct.

(D) During the day,plants perform both photosynthesis and respiration.
Photosynthesis produces $O_2$ and consumes $CO_2$,while respiration consumes $O_2$ and produces $CO_2$.
In a healthy,actively photosynthesizing plant,the rate of photosynthesis is significantly higher than the rate of respiration.
Experimental observations and physiological studies indicate that the amount of oxygen produced during photosynthesis is approximately $50$ times the amount of oxygen consumed during respiration in many active plants.
Therefore,the ratio of oxygen produced to oxygen consumed is $50:1$.

(B) Photosynthesis is the process by which green plants,algae,and cyanobacteria convert light energy into chemical energy.
In oxygenic photosynthesis,water $(H_2O)$ acts as an electron donor,resulting in the release of oxygen $(O_2)$ as a byproduct.
However,photosynthetic bacteria (such as purple and green sulfur bacteria) perform anoxygenic photosynthesis.
These bacteria use substances like hydrogen sulfide $(H_2S)$ or other organic compounds as electron donors instead of water,and therefore,they do not produce $O_2$ during the process.
Red algae,$C_4$ plants,and blue-green algae (cyanobacteria) all perform oxygenic photosynthesis.

(D) The evidence that oxygen released during photosynthesis comes from water is supported by:
$1$. The use of $O^{18}$ isotope labeling experiments (Ruben,Hassid,and Kamen),where $O^{18}$ labeled water $(H_2O^{18})$ resulted in the release of $O^{18}$ labeled oxygen gas $(O_2^{18})$,proving water is the source.
$2$. The Hill reaction,which demonstrated that isolated chloroplasts can evolve $O_2$ in the presence of artificial electron acceptors (like potassium ferricyanide) even without $CO_2$ fixation,provided water is present.
$3$. Studies on photosynthetic bacteria (like purple sulfur bacteria) show they use $H_2S$ instead of $H_2O$ as a hydrogen donor,resulting in the release of sulfur instead of oxygen,confirming that the oxygen source in plants is the water molecule.

(C) The transpiration ratio $(TR)$ is defined as the ratio of the number of moles of $H_2O$ transpired to the number of moles of $CO_2$ assimilated.
$C_3$ plants have a high transpiration ratio (typically $400-1000$) because they are less water-efficient.
$C_4$ plants have a lower transpiration ratio (typically $200-350$) compared to $C_3$ plants.
$CAM$ (Crassulacean Acid Metabolism) plants have the lowest transpiration ratio (typically $50-100$) because they open their stomata only at night,which significantly reduces water loss while fixing $CO_2$.

(D) Photosynthesis is a complex physiological process that occurs within the specialized organelles known as chloroplasts.
While the student provided the raw materials ($CO_2$,$H_2O$,chlorophyll,and light),these components must be organized within the structural framework of a living cell,specifically within the thylakoid membranes of the chloroplasts.
Chlorophyll alone,when extracted or added to a solution,cannot perform photosynthesis because it lacks the necessary protein complexes,electron transport chains,and the organized environment required to convert light energy into chemical energy.
Therefore,photosynthesis will not occur in this setup.

(A) Bacterial photosynthesis is anoxygenic,meaning it does not produce oxygen. Unlike green plants,bacteria do not possess the $PS-II$ complex,which is responsible for the photolysis of water. Most photosynthetic bacteria (like purple and green sulfur bacteria) contain only a single photosystem,which is analogous to $PS-I$ (specifically,a reaction center like $P870$ or $P840$). Therefore,they lack both the $PS-II$ complex and the water-splitting mechanism found in oxygenic photosynthesis.

(A) $RuBP$ carboxylase-oxygenase,commonly known as $RuBisCO$,is the most abundant protein in the chloroplast and indeed on Earth.
It is a key enzyme in the Calvin cycle,responsible for the fixation of atmospheric $CO_2$ into organic compounds during the light-independent reactions of photosynthesis.

(B) Transpiration is the evaporative loss of water by plants,which occurs mainly through the stomata in the leaves.
$C_3$ plants are generally less water-efficient compared to $C_4$ plants because they have a higher rate of photorespiration and require more water to fix the same amount of $CO_2$.
$CAM$ (Crassulacean Acid Metabolism) plants have evolved to keep their stomata closed during the day to minimize water loss,thus having the lowest transpiration rate.
$C_4$ plants have a specialized anatomy (Kranz anatomy) that allows them to fix $CO_2$ efficiently even with partially closed stomata,leading to a lower transpiration rate than $C_3$ plants.
Therefore,$C_3$ plants exhibit the highest rate of transpiration among the given options.

(D) Photosynthesis is the process by which green plants,algae,and some bacteria convert light energy into chemical energy.
In oxygenic photosynthesis,water $(H_2O)$ acts as an electron donor,and oxygen $(O_2)$ is released as a byproduct. This occurs in plants,algae,and cyanobacteria (blue-green algae).
However,in anoxygenic photosynthesis,other substances like hydrogen sulfide $(H_2S)$ act as electron donors instead of water. Consequently,sulfur or other compounds are produced instead of oxygen. This process is characteristic of certain photosynthetic bacteria,such as purple and green sulfur bacteria.

(C) Green plants in an aquarium perform photosynthesis during the day.
During the process of photosynthesis,plants consume $CO_2$ and release $O_2$ as a byproduct.
This released $O_2$ dissolves in the water,which is essential for the respiration of aquatic animals like fish.
Therefore,green plants are primarily grown to maintain the oxygen levels in the aquarium.

(A) Photosynthesis is the process by which autotrophs convert light energy into chemical energy.
In aquatic ecosystems,the primary producers are phytoplankton (microscopic algae and cyanobacteria).
These organisms are responsible for the vast majority of primary production in the oceans and other water bodies,accounting for a significant portion of the global oxygen production and carbon fixation.
Therefore,maximum photosynthesis occurs by phytoplankton.