In $$C_{4}$$ plants, Calvin cycle occurs in

Stroma of bundle sheath chloroplast

Grana of bundle sheath chloroplast

Does not occur as $$CO_{2}$$ is fixed mainly by PEP and no $$CO_{2}$$ is left for Calvin cycle

MCQ Questions for Class 11 Medical Biology Photosynthesis In Higher Plants Quiz 3

Which of the following cycle, shows oxalocetic acid as first stable product?

0%
Calvin cycle
0%
Hatch and Slack cycle
0%
$C_{2}$ cycle
0%
None of the above

Explanation

$C_4$ plants have developed a mechanism to efficiently deliver

$CO_2$ to the RuBisCO enzyme. They utilize their specific leaf anatomy, where chloroplasts exist not only in the mesophyll cells in the outer part of their leaves but in the bundle sheath cells as well. Instead of direct fixation to RuBisCO in the Calvin cycle,

$CO_2$ is incorporated into a 4-carbon organic acid, which has the ability to regenerate

$CO_2$ in the chloroplasts of the bundle sheath cells. Bundle sheath cells can then utilize this

$CO_2$ to generate carbohydrates by the conventional

$C_3$ pathway.

Which one of the following is a

$C_{4}$ plant?

0%
Spirogyra
0%
Pinus
0%
Sorghum
0%
Funaria

Explanation

Sorghum is an example for

$C_4$ plant, which is a genus of grasses with about 30 species, one of which is raised for grain and many of which are used as fodder plants, either cultivated or as a part of pasture. The plants are cultivated in warm climates worldwide.

Which of the following is CO

$_{2}$ acceptor in C

$_{4}$ plants?

0%
Phosphoenol pyruvate
0%
Ribulose 1,5- diphosphate
0%
Oxaloacetic acid
0%
Phosphoglyceric acid

Explanation

Phosphoenol pyruvic acid is an important chemical compound in biochemistry. It has the highest-energy phosphate bond found in living organisms, and is involved in glycolysis and gluconeogenesis. It is the primary

$CO_2$ acceptor in

$C_4$ plants.

$C_{4}$ plants, Calvin cycle occurs in

0%
Stroma of bundle sheath chloroplast
0%
Mesophyll chloroplast
0%
Grana of bundle sheath chloroplast
0%
Does not occur as $CO_{2}$ is fixed mainly by PEP and no $CO_{2}$ is left for Calvin cycle

Explanation

$C_4$ plants the photosynthesis takes place in a thin-walled mesophyll cell and a 4-carbon acid is handed off to a thick-walled bundle sheath cell, where the Calvin cycle occurs in a chloroplast of that second cell. This protects Calvin cycle from the effects of photorespiration.

$C_{4}$ plants are adapted to grow in

0%
Hot and dry climate
0%
Temperate climate
0%
Cold and dry climate
0%
Hot and humid climate

Explanation

The same active site of RUBISCO catalyze carboxylation and oxidation of ribulose 1,5-bisphosphate thereby competing with each other. Rate of oxidation reaction increases with increasing temperature much faster than the carboxylation reaction rate causing increased rate of photorespiration at higher temperatures. Spatial separation of carbon dioxide fixation and RUBISCO activity in mesophyll and bundle sheath cells of

$C_4$ plants respectively avoids photorespiration by concentrating

$CO_2$ in bundle sheath cells to scale down the oxygenase activity of RUBISCO and increase the RUBISCO efficiency even when stomata are close for long time to avoid trasnpiration loss and making the plants adapted to hot and dry conditions.

Dimorphism of chloroplast is found in

0%
$C_{4}$ plants
0%
$C_{3}$ plants
0%
CAM plants
0%
All of the above

Explanation

The most distinct feature of C ${_4}$ plants is the presence of bundle sheath with chloroplasts in the leaves. It is like a wreath around the vascular bundle. Hence, such anatomy is called Kranz anatomy. Bundle sheath may be single layered as in maize or double layered as in sugarcane. If two-layered, the outer one is green and the inner one is thick walled and called as the mestomal sheath. Mesophyll cell chloroplasts are granal and starch lacking but the bundle sheath cell chloroplasts are grana-lacking and starch-rich. Such feature of having two types of chloroplasts is known as chloroplast dimorphism.

Which one of the following is wrong in relation to photorespiration?

0%
It is a characteristic of $C_{3}$ plants.
0%
It occurs in chloroplasts.
0%
It occurs in day time only.
0%
It is a characteristic of $C_{4}$ plants.

Explanation

Photorespiration is absent in

$C_4$ plants due to the presence of a special structure called as kranz anatomy in their leaves. It is a process which takes place in

$C_3$ plants when carbon dioxide concentration in plants become low.

Agranal chloroplasts occur in

0%
Succulents
0%
$C_{4}$ plants
0%
Hydrophytes
0%
$C_{3}$ plants

Explanation

Presence of agranal chloroplast in bundle sheath is the characteristic feature of

$C_4$ plants. It could be identified by different light scattering experiments.

Atriplex spongiosa is a

0%
$C_{3}$ plant
0%
$C_{4}$ plant
0%
CAM plant
0%
All of the above

Explanation

Atriplex is a plant genus of 250-300 species. A few Atriplex species are

$C_3$ plants, but most species are

$C_4$ plants with a characteristic leaf anatomy - kranz anatomy.

Photosynthesis in

$C_{4}$ plants is relatively less limited by atmospheric

$CO_{2}$ levels because

0%
Four carbons acids are the primary initial $CO_{2}$ fixation products.
0%
The primary fixation of $CO_{2}$ is mediated via PEP carboxylase.
0%
Effective pumping of $CO_{2}$ into bundle sheath cells takes place.
0%
RuBisCO in $C_{4}$ plants has higher affinity for $CO_{2}$ .

Explanation

$_2$ concentration of the atmosphere is 360 ppm. It is a limiting factor for C

$_3$ as the available CO

$_2$ concentration is lower than the optimum for photosynthesis. Increase in its concentration upto 0.05% increases the rate of photosynthesis in most C

$_3$ plants. When CO

$_2$ concentration is reduced, there comes a point at which illuminated plant parts stop absorbing CO

$_2$ from their environment. It is called as CO

$_2$ compensation point or threshold value. The C

$_4$ plants have this compensation value low as they are more efficient in CO

$_2$ fixation through PEP- Carboxylase. The optimum CO

$_2$ concentration for C

$_4$ plants is 360 ppm. But the atmospheric conc of CO

$_2$ is increasing. If the trend of CO

$_2$ increase continues then that would be harmful for C

$_4$ plants.

Sugarcane shows high efficiency of

$CO_{2}$ fixation because of

0%
Calvin cycle
0%
Hatch and Slack cycle
0%
TCA cycle
0%
Greater sunlight

Explanation

A metabolic pathway first defined by M.D. Hatch and C.R. Slack in 1966 to reduce photorespiration. In this pathway, the $CO_2$ is first added to phosphoenolpyruvate by the enzyme PEP carboxylase, producing the four carbon compound in mesophyll cells, that is later transported to bundle sheath cells to liberate the $CO_2$ for use in the Calvin cycle.

Which crop utilises solar energy most efficiently?

0%
Potato
0%
Sugarcane
0%
Wheat
0%
Rice

Explanation

The same active site of RUBISCO catalyze carboxylation and oxidation of ribulose 1,5-bisphosphate thereby competing with each other. Under standard 25°C, the rate of the carboxylation reaction is four times that of the oxidation reaction and 20% of fixed carbon is lost in photorespiration. Spatial separation of carbon dioxide fixation and RUBISCO activity in mesophyll and bundle sheath cells of

$C_4$ plants respectively avoids photorespiration by concentrating

$CO_2$ in bundle sheath cells to scale down the oxygenase activity of RUBISCO and increase the RUBISCO efficiency. Among the given options, sugarcane is a

$C_4$ plant and rest are

$C_3$ plants. Correct answer is B.

An example of

$C_{4}$ plant is:

0%
Maize
0%
Rice
0%
Wheat
0%
Potato

Which of the following statement regarding

$C_{4}$ plants is false?

0%
The primary $CO_{2}$ acceptor is a 5 carbon molecule.
0%
The initial carboxylation reaction occurs in mesophyll.
0%
The leaves that fix $CO_{2}$ have two cell types.
0%
The chloroplasts are dimorphic.
0%
The Calvin pathway does not take place in the mesophyll cells but does so only in the bundle sheath cells.

Explanation

The primary carbon dioxide acceptor in

$C_4$ plants is phosphoenol pyruvate (PEP), which is a 3 carbon compound. The first stable compound is a 4 carbon compound, oxaloacetic acid.

Chloroplasts without grana are known to occur in

0%
Bundle sheath cells of $C_{3}$ plants
0%
Mesophyll cells of $C_{4}$ plants
0%
Bundle sheath cells of $C_{4}$ plants
0%
Mesophyll cells of all plants

Photorespiration is favoured by:

0%
Low light and high $O_{2}$
0%
Low $O_{2}$ and high $CO_{2}$
0%
Low temperature and high $O_{2}$
0%
High $O_{2}$ and low $CO_{2}$

Explanation

Correct option: D

Explanation:

Photorespiration is favoured by High $O_2$ and low $CO_2$ . It occurs when the $CO_2$ levels inside a leaf become low.
RuBP instead of being converted to 2 molecules of PGA binds with $O_2$ (high concentration) to form one molecule of phosphoglycerate and phosphoglycolate. There is no synthesis of ATP or NADPH or sugars.
It is seen in hot and dry weather when stomata are closed to prevent excess water loss.

Thus, Option D is correct.

Correlation between Kranz anatomy and

$C_{4}$ pathway of

$CO_{2}$ assimilation was first established by

0%
Hill and Bendall
0%
Calvin
0%
Downton and Treguna
0%
Arnold

Explanation

The metabolic pathway of

$C_4$ photosynthesis was first described in 1980s by Hatch and Slack. The integrated picture of

$C_4$ photosynthesis was quickly formulated from the physiology, structure and ecology that were associated with the group of plants known to have Kranz anatomy by Downton and Treguna by 1968.

In the leaves of

$C_{4}$ plants, malic acid formation during

$CO_{2}$ fixation occurs in the cells of:

0%
Mesophyll
0%
Bundle sheath
0%
Phloem
0%
Epidermis

$C_{4}$ plants, the carbon dioxide fixation occurs in

0%
Guard cells
0%
Spongy cells
0%
Palisade cells
0%
Bundle sheath cells

Explanation

$C_4$ plants conduct

$C_4$ cycle in mesophyll cells and Calvin cycle (fixation of carbon) in bundle sheeth cells. The C4 pathway in mesophyll cells includes carboxylation of phosphoenolpyruvate into oxaloacetate. The oxaloacetate is then converted into the intermediate malate, which is transported bundle-sheath cell. Malate is decarboxylated to produce pyruvate and enters the Calvin cycle. Correct answer is D.

Peroxisomes are found in

0%
Bundle sheath
0%
Endospem
0%
Mesophyll cell
0%
Vascular bundle

In Hatch and Slack pathway the

0%
Chloroplasts are of same type
0%
Occurs in Kranz anatomy, where mesophyll cells have small chloroplasts whereas bundle sheath cells have agranal chloroplasts
0%
Occurs in Kranz anatomy, where mesophyll cells have small chloroplasts whereas bundle sheath cells have larger chloroplasts
0%
Kranz anatomy, where mesophyll cells are diffused

Explanation

Hatch and Slack pathway is the other name for

$C_4$ cycle, named after the discoverers.

$C_4$ plants have a characteristic feature called as Kranz anatomy in mesophyll. They have small chloroplast in mesophyll, whereas agranal chloroplast in bundle sheath.

Photorespiration takes place only in

0%
Lysosomes of plant cell
0%
Yellow parts of the plant
0%
Mitochondria of plant cell
0%
None of the above

Explanation

Photorespiration is a process in plant metabolism, which attempts to reduce the consequences of a wasteful oxygenation reaction by the enzyme RuBisCO. This process reduces efficiency of photosynthesis, potentially reducing photosynthetic output by 25% in

$C_3$ plants. Photorespiration involves a complex network of enzyme reactions, that exchange metabolites between chloroplasts, leaf peroxisomes and mitochondria.

In photorespiration, glycolate is converted to

$CO_{2}$ and serine in

0%
Chloroplast
0%
Peroxisomes
0%
Vacuoles
0%
Mitochondria

Photorespiration is also called

0%
$C_{2}$ cycle
0%
$C_{3}$ cycle
0%
$C_{4}$ cycle
0%
$CAM$ cycle

Explanation

Photorespiration occurs when carbon dioxide level becomes low inside a leaf. This happens on hot dry days, when a plant is forced to close its stomata to prevent excess water loss.
If the plant continues to attempt to fix $CO_2$ , when its stomata are closed, the $CO_2$ will get used up and the $O_2$ ratio in the leaf increase relative to $CO_2$ concentrations.
Thus, the enzyme RuBP oxygenase fixes oxygen instead of carbon dioxide and produces two molecules of phosphoglycolate (2C). It is also called $C_2$ cycle.

So, the correct answer is '

$C_2$ cycle.'

Number of carboxylation in

$C_{4}$ cycle is

0%
1
0%
2
0%
5
0%
3

Explanation

$C_4$ cycle has two carboxylations in it. In C

$C_4$ plants, after entering through stomata, CO₂ diffuses into a mesophyll cell. Being close to the leaf surface, these cells are exposed to high levels of O₂, but have no RUBISCO so cannot start photorespiration (nor the dark reactions of the Calvin cycle). Instead, the CO₂ is inserted into a 3-carbon compound (C₃) called phosphoenolpyruvic acid forming the 4-carbon compound oxaloacetic acid. Oxaloacetic acid is converted into malic acid or aspartic acid (both have 4 carbons), which is transported into bundle sheath cells. Here the 4-carbon compound is broken down into carbon dioxide, which enters the Calvin cycle to form sugars and starch. Pyruvic acid is transported back to a mesophyll cell where it is converted back into PEP.

The first reaction in photorespiration is

0%
Carboxylation
0%
Decarboxylation
0%
Oxygenation
0%
Phosphorylation

In sugarcane plant,

$^{14}CO_{2}$ is fixed in malic acid. Which enzyme is responsible for fixing

$CO_{2}$ ?

0%
Fructose phosphatase
0%
Ribulose biphosphate carboxylase
0%
Phosphoenol pyruvic acid carboxylase
0%
Ribulose phosphate kinase

Explanation

Phosphoenol pyruvate is formed from the decarboxylation of oxloacetate and hydrolysis of one guanosine triphosphate molecule. This reaction is catalyzed by the enzyme phosphoenolpyruvate carboxylase. This reaction is a rate limiting step in gluconeogenesis.

GTP + Oxaloacetate -----> GDP + Phosphoenolpyruvate + $CO_2$ .

Which of the following is not a

$C_{4}$ plant?

0%
Sugarcane
0%
Maize
0%
Sorghum
0%
Wheat

Explanation

Examples of

$C_3$ plants: beans, rice, wheat, potatoes, most temperate crops and all woody trees.
Examples for

$C_4$ plants: corn, sugarcane, amaranth, mostly grasses, but some shrubs too, which are cold tolerant.

In Kranz anatomy, the bundle sheath cells have

0%
Thin walls, no intercellular spaces and several mitochondria
0%
Thin walls, many intercellular spaces and few chloroplast
0%
Thin walls, many intercellular spaces and no chloroplast
0%
Thik walls, no intercellular spaces and large number of chloroplast

Which one is false about kranz anatomy?

0%
Bundle sheath have large chloroplast and less developed grana.
0%
Mesophyll cells have large chloroplasts.
0%
It is found in atriplex, sugarcane, maize.
0%
Plant having it have better photosynthesizing power than $c_{3}$ plants.

Explanation

In some plants, the first stable product after the fixation of

$CO_2$ is a 4 carbon dicarboxylic acid called Oxaloacetic acid (OAA). Such plants are called C4 plants. Examples are sugarcane, maize, some other monocot and dicot plants.

C4 plants have characteristic leaf anatomy and dimorphic Chloroplasts:

1. The leaf mesophyll consists of compactly packed cells and is not differentiated into palisade and spongy mesophyll.

2. The vascular bundles in leaves are surrounded by distinct bundle sheath of radially enlarged parenchyma cells.

3. The Chloroplasts in leaves are dimorphic: granal and agranal chloroplasts.

Chloroplasts in the mesophyll cells are smaller and possess grana and chloroplasts in the bundle sheath cells are larger and without grana.

This type of anatomy in C4 plants is called Kranz anatomy

Unlike C3 plants, photosynthesis of C4 plants is not inhibited by

$O_2$ .

They have a very low

$CO_2$ compensation point which is the ambient

$CO_2$ concentration at which the rate of $$CO_2$$ uptake (for photosynthesis) is balanced by the rate of

$CO_2$ evolution. For C3 plants it's value is 20-100μl/litre and for C4 plants it's value is 0-5μl/litre.

So, bundle sheath cells have the

$CO_2$ concentrating mechanism and there is suppression of photorespiratory loss of

$CO_2$ . Therefore C4 plants have better photosynthesizing power than C3 plants.

So, the correct answer is B.

A process that makes important difference between

$C_{3}$ and

$C_{4}$ plants is

0%
Transpiration
0%
Glycolysis
0%
Photosynthesis
0%
Photorespiration

Explanation

RUBISCO has affinity for both oxygen and carbon dioxide. Photorespiration is oxidation of RuBP, rather than carboxylation, by enzyme RUBISCO and formation of 2-phosphoglycolate. Under standard 25°C, the rate of the carboxylation reaction is four times that of the oxidation reaction and 20% of fixed carbon is lost in photorespiration. Spatial separation of carbon dioxide fixation and RUBISCO activity in mesophyll and bundle sheath cells of

$C_4$ plants respectively avoids photorespiration by concentrating

$CO_2$ in bundle sheath cells to scale down the oxygenase activity of RUBISCO and increase the RUBISCO efficiency which is not the case in

$C_3$ plants. Correct answer is D.

$C_{4}$ plants can fix carbon dioxide efficiently even in

0%
Low $CO_{2}$ concentration
0%
Low temperature
0%
High $O_{2}$ concentration
0%
Low water concentration

Explanation

$C_4$ plants use a supplementary method of

$CO_2$ uptake, which forms a 4-carbon molecule instead of the two 3-carbon molecules of the Calvin cycle. Hence, these plants are called

$C_4$ plants. They can effectively fix carbon in low carbon dioxide concentration as they have kranz anatomy.

Photorespiration takes place in:

0%
Chloroplast, mitochondria
0%
Mitochondria, peroxisome
0%
Chloroplasts, peroxisome, mitochondria
0%
Chloroplasts, cytoplasm, mitochondria

Explanation

Photorespiration is a process in C $_3$ plants that inhibits the rate of photosynthesis in the presence of high oxygen concentration in light. In the presence of a high concentration of oxygen, C $_3$ plants start releasing carbon dioxide in light during an extra input of oxygen.
It is an enzymatic process that involves specialized reactions which take place in three organelles in plants namely, chloroplasts, mitochondria, and peroxisomes.
In the presence of low carbon dioxide concentration, the enzyme RuBisCO acts as an oxygenase and splits a molecule of RUBP into 2-phosphoglycolic acid and 3-phosphoglyceric acid.

Thus, the correct answer is option C.

Peroxisomes are related in

0%
Photosynthesis
0%
Photorespiration
0%
Respiration
0%
None of the above

The chemiosmotic coupling hypothesis of oxidative phospohorylation proposes that adenosine triphosphate is formed because

0%
A Proton gradient forms across the inner membrane
0%
There is a change in the permeability of the inner mitochondria membrane toward adenosine diphosphate
0%
High energy bonds are formed in mitochondrial proteins
0%
ADP is pumped out of the matrix into the intermembrane space

Who is credited with identifying petro-crops

0%
Swaminathan
0%
Calvin
0%
Krebs
0%
Borlang

Respiration initiated in chloroplast and occurs in light is called as

0%
Aerobic respiration
0%
Anaerobic respiration
0%
Photorespiration
0%
Fermentation

ATP stands for

0%
Adenosine triphosphate
0%
Adenine diphosphate
0%
Adenosine tetraphosphate
0%
Adenine triphosphate

Chemiosmotic theory of ATP synthesis in the chloroplast and mitochondria is based on:

0%
Proton gradient
0%
Accumulation of Potassium ions
0%
Accumulation of Sodium ions
0%
Membrane potential

Chemiosmotic mechanism of ATP synthesis was proposed by

0%
Warburg
0%
Dickens
0%
Krebs
0%
P. Mitchell

Explanation

Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration or photosynthesis.
Peter D. Mitchell proposed the chemiosmotic hypothesis in 1961.
The theory suggests essentially that most ATP synthesis in respiring cells comes from the electrochemical gradient across the inner membranes of mitochondria by using the energy of $NADH_2$ and $FADH_2$ formed from the breaking down of energy-rich molecules such as glucose.
So, the correct answer is option D.

$C_{2}$ cycle is studied in

0%
$C_{4}$ plants
0%
Those showing photorespiration
0%
Both A and B
0%
None of the above

Explanation

Otto Warburg discovered that

$O_2$ inhibits photosynthesis in C3 plants. This phenomenon originally was known as the Warburg effect, but later it was recognized as the light-dependent release of

$CO_2$ due to oxygenase activity of RuBisCO which is a bifunctional enzyme because it can catalyze both the carboxylation and the oxygenation of RuBP. When there is low

$CO_2$ concentration, RuBisCO performs oxygenase activity. Oxygenation of RuBP produces one molecule of 3-phosphoglycerate and one of 2-phosphoglycolate.

2-phosphoglycolate produced by RuBisCO when it oxygenates RuBP can't be utilized within the Calvin cycle. The pathway by which 2-phosphoglycolate is further metabolized is called as glycolate pathway or C2 cycle or oxidative photosynthetic carbon cycle or simply photorespiration. This pathway involves three subcellular compartments, the chloroplasts, peroxisomes and mitochondria.

So, the correct answer is B.

Oxidative phosphorylation refers to

0%
Anaerobic production of ATP
0%
The citric acid cycle production of ATP
0%
Production of ATP by chemiosmosis
0%
Alcoholic fermentation

Chemiosmotic theory of ATP synthesis in the chloroplasts is based on:

0%
Membrane potential
0%
Accumulation of K ions
0%
Proton gradient
0%
Accumulation of Na ions

Explanation

According to the chemiosmosis theory of ATP generation. The ATP is generated utilizing the electrochemical gradient generated due to the accumulation of protons in the thylakoid lumen of the chloroplast.
The accumulation of protons gives rise to an electric gradient, due to the accumulation of positive charge and a chemical gradient due to the accumulation of hydrogen atoms.
F $_0$ - F $_1$ ATP synthase enzyme complex, ATP generation occurs.

Which of the following is non-enzymatic phosphorylation

0%
Formation of fructose 1,6-diphosphate
0%
Formation of dihydroxyacetone phosphate
0%
Formation of 1,3-diphosphoglyceraldehyde
0%
All the above

Who got a Nobel prize for tracing the path of carbon in dark reaction?

0%
Benson and Basham
0%
Calvin
0%
Ruben
0%
Both A and B

Which of the following statement/s is/are true for maize (Zea mays)?
i.

$CO_2$ is fixed only once in the process of photosynthesis.
ii.

$CO_2$ is fixed twice in the process of photosynthesis.
iii. It undergoes the process of photorespiration.
iv.

$CO_2$ can be fixed even in very low concentrations during photosynthesis.

0%
(i) & (iii)
0%
(ii) only
0%
(i) & (iv)
0%
(ii) & (iv)

Explanation

The maize plant is a C

$_4$ plant and can fix the carbon dioxide twice in the process of photosynthesis by PEP carboxylase and RuBisCo. These plants do not undergo the process of transpiration. The plants can fix carbon dioxides at very low concentrations due to the enzyme PEP carboxylase.

Thus, the correct answer is option D.

Photosynthesis in C

$_{4}$ plants is relatively less limited by atmospheric CO

$_{2}$ levels because

0%
The primary fixation of CO $_{2}$ is mediated via PEP carboxylase
0%
Effective pumping of CO $_{2}$ into bundle sheath cells
0%
Four carbon acids are the primary initial CO $_{2}$ fixation products
0%
Rubisco in C4 plants has higher affinity for CO $_{2}$ .

Which of the following photosynthetic pigments are called biliproteins?

0%
Chlorophyll a
0%
Chlorophyll b
0%
Phycobillins
0%
Carotenoids

Sugarcane and corn are one of the most efficient plants in trapping light energy because

0%
They have ${C_4}$ acid cycle
0%
They do not involve photorespiration
0%
They perform Calvin cycle
0%
All of the above

Explanation

The plants such as sugarcane and maize which are adapted to dry tropical regions have an additional pathway of carbon dioxide fixation known as

$C_4$ pathway. These plants can absorb

$CO_2$ even from a much low

$CO_2$ concentration when the

$C_3$ plants fail to avail. Thus,

$C_4$ plants can perform a high rate of photosynthesis even when the stomata are nearly closed. They also maintain a high rate of photosynthesis under conditions of water shortage where the

$C_3$ plants would stop photosynthesis. Presence of excess

$O_2$ in the surrounding has no inhibitory effect on

$C_4$ pathway because the enzyme PEP- carboxylase which is the primary acceptor of

$CO_2$ is insensitive to

$O_2$ whereas in case of

$C_3$ plants RUBISCO is sensitive to

$O_2$ and starts combining with oxygen instead of

$CO_2$ and thus starts photorespiration. Photorespiration inhibits the rate of photosynthesis in these plants. On the other hand, photorespiration is absent in

$C_4$ plants which are of great advantage to them and helps in conserving water.

Thus, the correct answer is option B.

During photorespiration, the oxygen consuming reaction(s) occur in.

0%
Stroma of chloroplasts and peroxisomes
0%
Grana of chloroplasts and peroxisomes
0%
Stroma of chloroplasts
0%
Stroma of chloroplasts and mitochondria

CBSE Questions for Class 11 Medical Biology Photosynthesis In Higher Plants Quiz 3 - MCQExams.com

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Practice Class 11 Medical Biology Quiz Questions and Answers

CBSE Questions for Class 11 Medical Biology Photosynthesis In Higher Plants Quiz 3 - MCQExams.com

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Practice Class 11 Medical Biology Quiz Questions and Answers

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