Mix Examples- Photosynthesis in Higher Plants Questions in English

(D) $Rhodospirillium$ is a photosynthetic bacterium. It is a purple non-sulfur bacterium that utilizes light energy to perform photosynthesis,thereby fixing atmospheric $CO_2$ into carbohydrates.

(A) Photosynthetic bacteria (such as purple and green sulfur bacteria) do not evolve oxygen during photosynthesis. This is because they use $H_2S$ (hydrogen sulfide) as a hydrogen donor instead of $H_2O$ (water). Consequently,they release sulfur or sulfate as a byproduct instead of oxygen.

(C) Green algae perform photosynthesis when illuminated,which results in the release of oxygen $(O_2)$ as a byproduct.
Motile aerobic bacteria require oxygen for their metabolic processes and respiration.
Therefore,these bacteria accumulate in regions where oxygen concentration is highest,which is near the photosynthesizing green algae.

(B) Photosynthesis is a two-stage process consisting of light-dependent reactions (photo-chemical) and light-independent reactions (thermo-chemical or Calvin cycle).
These reactions occur within the chloroplast of plant cells.
The light-dependent reactions take place in the thylakoid membranes,while the light-independent reactions occur in the stroma of the chloroplast.

(B) The size of the stomatal pore varies from species to species.
For example,a fully opened stomatal pore of $Zea \ mays$ (Maize) measures $26 \ \mu m$ in length and $4 \ \mu m$ in width.
The average length of stomata in plants typically ranges from $20-28 \ \mu m$ and the breadth ranges from $3-10 \ \mu m$.

(A) When a twig with green leaves is placed in water under sunlight,the leaves continue to perform physiological processes.
However,the question implies the observation of gas bubbles or the movement of water.
Actually,in this specific experimental setup,the leaves release oxygen bubbles due to photosynthesis,but the question is often used to demonstrate the release of gases or the process of transpiration if the twig were not fully submerged.
Given the standard context of such biology experiments,if the leaves are submerged,the bubbles observed are due to photosynthesis.
However,if the question refers to the loss of water from the surface,it is transpiration.
In the context of standard biology curriculum,this setup is most commonly used to demonstrate photosynthesis by observing oxygen bubbles.

(B) The theory of photosynthesis in guard cells was proposed by $Von \ Mohl$ in $1856$.
He suggested that the chloroplasts present in the guard cells perform photosynthesis,which leads to the production of osmotically active substances (like sugars).
This increase in solute concentration lowers the water potential of the guard cells,causing water to enter via osmosis,which leads to the opening of the stomata.

(D) In higher plants,the transport of food materials (photosynthates) from the leaves (source) to other parts of the plant (sink) occurs through a specialized vascular tissue known as the phloem.
Phloem consists of sieve tube elements,companion cells,phloem parenchyma,and phloem fibers.
Sieve tube elements are the primary conducting cells for the translocation of sugars and other organic nutrients.

(D) In higher plants,several mineral elements are essential for the process of photosynthesis.
$Mg^{2+}$ is the central atom of the chlorophyll molecule,which is essential for light absorption.
$Mn^{2+}$ is required for the photolysis of water during the light-dependent reactions.
$Fe^{2+/3+}$ is a crucial component of cytochromes and ferredoxin,which are involved in the electron transport chain.
$Cu^{2+}$ is a component of plastocyanin,which acts as an electron carrier in the photosynthetic electron transport chain.
Therefore,the correct combination of ions involved in photosynthesis is $Mg, Cu, Mn, Fe$.

(D) The Warburg effect refers to the inhibition of photosynthesis in $C_3$ plants by high concentrations of oxygen $(O_2)$.
McAlister and Mayer conducted pioneering studies on this phenomenon using various leguminous plants.
They specifically demonstrated that the rate of photosynthesis in plants like Pea ($Pisum$ $sativum$),Arachis ($Arachis$ $hypogaea$),and Soybean ($Glycine$ $max$) is inhibited by increased levels of $O_2$.
Therefore,all the listed plants were subjects of their study regarding the Warburg effect.

(B) The correct statement is that photosynthesis consists of a light and dark reaction.
Blackman proposed the 'Law of Limiting Factors',which states that if a process is conditioned as to its rapidity by a number of separate factors,the rate of the process is limited by the pace of the slowest factor.
He also demonstrated that photosynthesis is a two-step process: a photochemical reaction (light reaction) and a biochemical reaction (dark reaction).

(C) $Chlorella$ $vulgaris$ and $Scenedesmus$ are two unicellular algae of the class $Chlorophyceae$.
These organisms are extensively used in photosynthetic research because they possess a simple structure,contain pure forms of chlorophyll,and are easy to isolate and culture in laboratory conditions.

(D) $Cuscuta$ $reflexa$ is a parasitic plant that lacks chlorophyll.
Because it does not contain chlorophyll,it cannot perform the process of photosynthesis.
Instead,it derives its nutrition from the host plant using specialized structures called haustoria.
Therefore,the correct answer is that it shows no photosynthesis at all.

(C) The correct answer is $C$.
Approximately $90\%$ of the total photosynthesis on Earth is carried out by aquatic plants,primarily algae.
Specifically,about $80\%$ of this occurs in oceans and $10\%$ in freshwater ecosystems.
Only about $10\%$ of the total global photosynthesis is performed by terrestrial (land) plants.

(B) The correct answer is $B$.
Photosynthesis is the process by which green plants,algae,and some bacteria convert light energy into chemical energy.
During photosynthesis,plants consume $CO_2$ and release $O_2$ as a byproduct.
Conversely,during cellular respiration,living organisms consume $O_2$ and release $CO_2$.
This continuous cycle of gas exchange between photosynthesis and respiration maintains the atmospheric balance of $CO_2$ and $O_2$.

(C) Both photosynthesis and chemosynthesis are processes used by organisms to synthesize organic compounds from inorganic substances.
In photosynthesis,light energy is used to drive the synthesis of organic compounds.
In chemosynthesis,energy is derived from the oxidation of inorganic chemical compounds.
Since both processes allow organisms to produce their own food without relying on other organisms for organic carbon,they are both classified as methods of autotrophic nutrition.

(B) Photosynthesis is the biological process by which green plants,algae,and some bacteria convert light energy into chemical energy.
During this process,solar energy is trapped by chlorophyll pigments and used to synthesize organic compounds like glucose from carbon dioxide and water.
This stored chemical energy is later utilized by organisms for various metabolic activities.

(C) Photosynthesis is an anabolic and endothermic process.
It is a mechanism of synthesis of food where simple inorganic substances like $CO_2$ and $H_2O$ are converted into complex organic compounds like glucose using light energy.
Since it involves the building up of complex molecules from simpler ones,it is classified as an anabolic process.

(C) The correct option is $C$.
Chloroplasts are the sites of photosynthesis where they fix atmospheric $CO_2$ into carbohydrates (glucose).
The amount of $CO_2$ fixed by one gram of chlorophyll in one hour is known as the photosynthetic number or assimilation number.

(D) The correct answer is $D$.
Photosynthesis is a complex process where green plants synthesize energy-rich organic compounds like carbohydrates from simple inorganic substances like $CO_2$ and water.
This process requires light energy (usually sunlight) and the pigment chlorophyll to capture that energy.
Since light,chlorophyll,$CO_2$,and water are all essential components for the synthesis of organic matter,all the given options are necessary.

(C) The correct answer is $C$.
Burning of sugar (combustion),respiration in plants,and the heating of limestone $(CaCO_3 \rightarrow CaO + CO_2)$ all result in the release of $CO_2$.
In contrast,photosynthesis by green plants is a process where plants consume $CO_2$ from the atmosphere and release $O_2$ as a byproduct,thereby reducing the concentration of $CO_2$ rather than forming it.

(C) . Plant physiology is the branch of botany that deals with the life processes and functional activities of plants,including photosynthesis,water absorption,and transpiration.

(D) Photosynthesis is a biological process that utilizes water as a source of electrons and protons.
Scientific estimates suggest that the total amount of water present on Earth is approximately $1.386 \times 10^9 \ km^3$.
Based on the global rate of photosynthesis,it is calculated that the total volume of water split by all photosynthetic organisms on Earth over a period of $2$ million years is approximately $25$ million $km^3$.
Therefore,the correct option is $D$.

(D) Photosynthesis is the process by which green plants synthesize organic food (glucose) using $CO_2$ and water in the presence of sunlight and chlorophyll.
$1.$ Water and minerals are essential for plant growth and as raw materials for photosynthesis.
$2.$ Light and chlorophyll are necessary for the absorption of energy and the light-dependent reactions.
$3.$ $CO_2$ is the primary carbon source for the synthesis of carbohydrates,and an optimum temperature is required for enzyme activity (like RuBisCO).
$4.$ Oxygen is a byproduct released during the light-dependent reactions,and sucrose is the end product of photosynthesis (transported form of sugar). Therefore,oxygen and sucrose are not raw materials required for the process to occur; they are products.

(C) The process of photosynthesis involves the synthesis of carbohydrates using $CO_2$,$H_2O$,light energy,and chlorophyll.
$CO_2$ acts as the carbon source,$H_2O$ provides electrons and protons,and chlorophyll captures light energy.
Nitrogen is an essential nutrient for plants but is not directly involved in the light-dependent or light-independent reactions of photosynthesis for carbohydrate synthesis.
Therefore,the correct answer is $C$.

(D) Photosynthesis is a fundamental biological process for several reasons:
$1$. Synthesis of food: It converts light energy into chemical energy,producing glucose which serves as the primary food source for almost all living organisms.
$2$. Purification of the atmosphere: It consumes $CO_2$ and releases $O_2$,which is essential for the respiration of aerobic organisms and helps maintain the balance of gases in the atmosphere.
$3$. Providing vast resources of energy: Fossil fuels like coal,petroleum,and natural gas are essentially stored solar energy captured by plants through photosynthesis millions of years ago.
Therefore,all the given options are correct.

(C) The aerobic atmosphere is maintained by plants because they perform photosynthesis.
During the process of photosynthesis,plants utilize $CO_2$ and water in the presence of sunlight and chlorophyll to produce glucose and release $O_2$ as a byproduct.
This continuous release of $O_2$ into the atmosphere is essential for the survival of aerobic organisms.

(B) The correct answer is $B$. Photosynthesis is the unique process that supports life on Earth because it is the primary source of all food on Earth. It produces organic compounds (glucose) which serve as the energy source for almost all living organisms and releases $O_2$ as a byproduct, which is essential for the respiration of aerobic organisms.

(B) The balanced chemical equation for photosynthesis is:
$6CO_2 + 12H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2 + 6H_2O$
From the equation,it is clear that for the reduction of $6$ molecules of $CO_2$ to produce $1$ molecule of hexose $(C_6H_{12}O_6)$,$12$ molecules of water $(H_2O)$ are required.

(C) The correct answer is $C$. Photosynthesis and respiration are not alike in many ways.
In photosynthesis,$O_2$ is evolved and $CO_2$ is taken in,whereas in respiration,this process is exactly opposite.
Additionally,carbohydrates are synthesized during photosynthesis,while the oxidation of carbohydrates takes place during respiration.

(D) The correct answer is $D$.
Starch is the detectable end product of photosynthesis.
During the process of photosynthesis,plants produce glucose as the primary sugar.
However,glucose is highly reactive and soluble,so it is quickly converted into starch,which is an insoluble polysaccharide.
Starch serves as a stable storage form of carbohydrates in plant cells and can be easily detected using iodine solution,which turns blue-black in its presence.

(B) The sugar produced during photosynthesis is primarily glucose. In the majority of plants,this glucose is converted into starch for storage.
Starch is preferred as a storage molecule because it is highly stable,compact,and water-insoluble,which prevents it from affecting the osmotic potential of the cell.

(B) . Photosynthesis by plants is the most vital process for the existence of life on earth because it helps to maintain the equilibrium of $O_2$ and $CO_2$ in the atmosphere.
It purifies the air and synthesizes food for all living beings,serving as the primary source of energy for nearly all ecosystems.

(B) The correct answer is $B$. Plants are known as purifiers of air because they perform photosynthesis.
During the process of photosynthesis,plants absorb $CO_2$ from the atmosphere and release $O_2$ as a byproduct.
This exchange helps in maintaining the balance of gases in the atmosphere,thereby purifying the air.

(D) The correct matches are as follows:
$(A)$ Emerson effect: This refers to the enhancement of the rate of photosynthesis when light of two different wavelengths is provided simultaneously,involving both $(d)$ Photosystem-$I$ and $II$.
$(B)$ Hill reaction: This describes the light-driven splitting of water molecules,known as $(b)$ Photolysis,which releases oxygen.
$(C)$ Calvin cycle: This is the primary pathway for carbon fixation in plants,also known as the $(c)$ $C_3$ cycle.
$(D)$ Hatch and Slack cycle: This is the pathway for carbon fixation in certain plants,also known as the $(a)$ $C_4$ cycle.
Therefore,the correct matching is $A-d, B-b, C-c, D-a$.

(D) The correct matching is as follows:
$A$. Grana of chloroplast is the site for the light reaction of photosynthesis.
$B$. Stroma of chloroplast is the site for the dark reaction (Calvin cycle) of photosynthesis.
$C$. Cytoplasm is the site for glycolysis, which is the initial stage of cellular respiration.
$D$. Mitochondrial matrix is the site for the Kreb's cycle ($TCA$ cycle).
Therefore, the correct combination is $A-2, B-3, C-4, D-1$.

(C) In photosynthesis,the light-dependent reactions involve the synthesis of $ATP$ from $ADP$ and inorganic phosphate,a process known as photophosphorylation.
This process occurs in two distinct ways: cyclic photophosphorylation and non-cyclic photophosphorylation.
In cyclic photophosphorylation,only $Photosystem-I$ $(PS-I)$ is involved,and electrons circulate back to the reaction center,resulting in the production of $ATP$ but not $NADPH$.
In non-cyclic photophosphorylation,both $Photosystem-II$ $(PS-II)$ and $Photosystem-I$ $(PS-I)$ are involved,leading to the production of both $ATP$ and $NADPH$.
Therefore,both types of phosphorylation take place during photosynthesis.

(B) The quantum requirement in photosynthesis is $8$,which means $8$ quanta of light are required to evolve $1 \text{ mol}$ of ${O_2}$.
Quantum yield is defined as the reciprocal of the quantum requirement.
Therefore,quantum yield = $1/8 = 0.125$.
Expressed as a percentage,$0.125 \times 100 = 12.5\%$,which is approximately $12\%$.

(B) The photosynthetic equation is $6CO_2 + 12H_2O + \text{Light Energy} \rightarrow C_6H_{12}O_6 + 6O_2 + 6H_2O$.
To synthesize $1 \ mole$ of glucose,$686 \ kcal$ of energy is stored in the chemical bonds.
Photosynthesis is not $100\%$ efficient.
According to the quantum requirement,$8 \ quanta$ are required to evolve $1 \ mole$ of $O_2$.
For $1 \ mole$ of glucose,$6 \ moles$ of $O_2$ are evolved,thus requiring $6 \times 8 = 48 \ quanta$ (moles of photons).
In the blue region $(400 \ nm)$,$1 \ mole$ of quanta provides $72 \ kcal$. Total energy required = $48 \times 72 = 3456 \ kcal$.
In the red region $(700 \ nm)$,$1 \ mole$ of quanta provides $41 \ kcal$. Total energy required = $48 \times 41 = 1968 \ kcal$.
Thus,the range of energy required is $1968 \ to \ 3456 \ kcal$.

(C) In $Cyclic$ $photophosphorylation$,electrons are cycled back to the $Photosystem$ $I$ $(PSI)$ reaction center,and the energy released during electron transport is used to pump protons,creating a proton gradient that drives $ATP$ synthesis.
In $Non-cyclic$ $photophosphorylation$,both $PSI$ and $PSII$ are involved. The electron flow from $PSII$ to $PSI$ and finally to $NADP^+$ also generates a proton gradient across the thylakoid membrane,which leads to the synthesis of $ATP$ along with $NADPH$.
Therefore,$ATP$ is produced in both processes.

(A) Photophosphorylation is the process of synthesizing $ATP$ from $ADP$ and inorganic phosphate using light energy in the chloroplasts.
Oxidative phosphorylation is the process of synthesizing $ATP$ from $ADP$ and inorganic phosphate using energy derived from the oxidation of nutrients (like glucose) in the mitochondria.
$1$. Photophosphorylation occurs specifically in the presence of light,whereas oxidative phosphorylation can occur in the dark as long as substrates are available.
$2$. Both processes involve the formation of $ATP$ and the participation of cytochromes in the electron transport chain.
$3$. Therefore,the primary difference among the given options is that photophosphorylation is light-dependent.

(D) In green plant cells,in the presence of sunlight,$ATP$ is produced primarily through photophosphorylation during the light-dependent reactions of photosynthesis.
However,plant cells also perform oxidative phosphorylation in the mitochondria for cellular respiration and substrate-level phosphorylation during glycolysis and the Krebs cycle.
Since the question asks for methods responsible for $ATP$ production in the presence of sunlight,and all three processes occur simultaneously in a living plant cell under light conditions,the correct answer is $D$.

(B) The overall chemical equation for photosynthesis is $6CO_2 + 12H_2O \rightarrow C_6H_{12}O_6 + 6O_2 + 6H_2O$.
The total energy required to reduce $6$ molecules of $CO_2$ to form one molecule of glucose is approximately $686$ $kcal$.
To find the energy required for the reduction of one molecule of $CO_2$,we divide the total energy by $6$: $686 / 6 \approx 114.3$ $kcal$.
Among the given options,$110$ $kcal$ is the closest approximation to the energy required for the reduction of one molecule of $CO_2$.

(D) $CAM$ stands for Crassulacean Acid Metabolism. This metabolic pathway was first reported in $Bryophyllum$,a member of the family Crassulaceae,hence the name. It is an adaptation primarily found in succulent plants $(xerophytes)$ that live in arid environments,such as members of the Cactaceae family (e.g.,$Opuntia$),Crassulaceae,and some species in Chenopodiaceae. Therefore,all the listed plant families contain members that exhibit the $CAM$ cycle.

(C) Photosynthetic efficiency varies between plant types due to their carbon fixation pathways.
$C_3$ plants,such as wheat and rice,have a lower photosynthetic rate compared to $C_4$ plants under optimal conditions.
The mean photosynthetic rate for $C_3$ plants is approximately $20-25$ mg of $CO_2$ per $dm^2$ per hour.
In contrast,$C_4$ plants,such as maize and sugarcane,exhibit a higher photosynthetic rate,typically ranging from $50-80$ mg of $CO_2$ per $dm^2$ per hour.
Therefore,the values $22$ mg and $75$ mg represent the approximate mean rates for $C_3$ and $C_4$ plants,respectively.

(B) $CAM$ stands for Crassulacean Acid Metabolism.
$CAM$ plants are adapted to arid environments where they open their stomata at night to minimize water loss through transpiration.
Pineapple $(Ananas \text{ } comosus)$ is a well-known example of a $CAM$ plant.
Maize is a $C_4$ plant, while Onion and Pea are $C_3$ plants.

(C) Anoxygenic photosynthesis is a process in which light energy is captured and converted to chemical energy without the production of oxygen.
This process is characteristic of certain groups of bacteria,such as green sulfur bacteria and purple bacteria.
Unlike plants,algae,and cyanobacteria,which use water as an electron donor and release oxygen as a byproduct,these bacteria use other substances like hydrogen sulfide $(H_2S)$ or organic compounds as electron donors,resulting in the absence of oxygen evolution.

(C) Photosynthetic bacteria generally possess only one photosystem ($PS-I$ or $PS-II$) and perform anoxygenic photosynthesis,meaning they do not evolve oxygen.
However,$Cyanobacteria$ are unique among photosynthetic bacteria because they perform oxygenic photosynthesis.
$Cyanobacteria$ contain both $PS-I$ and $PS-II$ in their thylakoid membranes,which allows them to perform non-cyclic photophosphorylation and split water molecules to release oxygen as a byproduct.

(D) Photosynthetic bacteria,such as purple bacteria,contain bacteriochlorophyll pigments that are capable of absorbing light in the infra-red region of the electromagnetic spectrum.
Specifically,these bacteria perform photosynthesis using wavelengths in the range of $850-950 \, nm$,which falls under the infra-red category. Therefore,among the given options,'Far red' is the most appropriate choice as it represents the longest wavelength range provided.

(B) $O_2$ is not liberated in bacteria during the process of photosynthesis. Their photosynthesis is non-oxygenic. This is because these bacteria use $H_2S$ (hydrogen sulfide) instead of $H_2O$ (water) as a hydrogen donor during the light-dependent reactions.