MCQ Questions for Class 11 Medical Biology Photosynthesis In Higher Plants Quiz 4

The name, Melvin Calvin is associated with

0%
Synthesis of ATP during photosynthesis
0%
Release of water during photosynthesis
0%
Carbon fixation during photosynthesis
0%
Capture light energy during photosynthesis

Explanation

The Calvin cycle is a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of

$CO_2$ and leaves in the form of sugar. The cycle spends ATP as an energy source and consumes

$NADPH_2$ as reducing power for adding high energy electrons to make the sugar. Melvin Ellis Calvin was an American chemist most famed for discovering the Calvin cycle along with Andrew Benson and James Bassham, for which he was awarded the 1961 Nobel Prize in chemistry.

The rate limiting step in photosynthesis is

0%
Light reaction
0%
Dark reaction
0%
Both (A) and (B)
0%
None of the above

First carbon fixation in

${C_4}$ pathway occurs in chloroplasts of

0%
Pallisade tissue
0%
Spongy mesophyll
0%
Bundle sheath
0%
Guard cells

Explanation

C carbon fixation is a metabolic pathway for carbon fixation in photosynthesis, along with C and CAM metabolic pathways. In C

$_{4}$ plants, for example maize, PEP carboxylase fixes bicarbonate in the mesophyll cells of the leaf and the resulting four-carbon compound, malate, is shuttled into the bundle sheath cells where it releases CO for fixation by RuBisCo. So, first carbon fixation in C

$_{4}$ plants occurs in spongy mesophyll cells. Thus, option B is correct and other options are incorrect.

While conversion of phosphoglyceric acid into phosphoglyceraldehyde during photosynthesis one of the following reactions occur

0%
Oxidation
0%
Reduction
0%
Electrolysis
0%
Hydrolosis

${C_4}$ plants are abundant in

0%
Temperate region with more humid conditions.
0%
Temperate region with more dry conditions.
0%
Tropical region with more humid conditions.
0%
Tropical region with more dry conditions.

Explanation

Plants using the C

$_4$ (Hatch-Slack) photosynthetic pathway are key for global food production and account for 25% of terrestrial primary productivity, mostly in relatively warm, dry regions.

So the correct option is 'Tropical region with more dry conditions'.

Ammonia is released by plants during

0%
C A M
0%
Dark respiration
0%
Photorespiration
0%
All of the above

Explanation

Photorespiration involves conversion of the phosphorylated phosphoglycolate to the amino acid glycine. This is followed by the conversion of two glycine molecules (two carbons each) to the amino acid serine (three carbons) plus one molecule of CO

$_{2}$ and one of ammonia. Thus, option C is correct.
Dark respiration is a form of respiration in plants where carbon dioxide is released without the aid of sunlight. Thus, option B is incorrect.
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO

$_{2}$ ). The CO

$_{2}$ is stored as the four-carbon acid malate, and then used during photosynthesis during the day. The pre-collected CO

$_{2}$ is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency. In CAM photosynthesis ammonia is not released. Thus, option A is also incorrect.

Dimorphism of chloroplast is found in

0%
${C_4}$ plants
0%
${C_3}$ plants
0%
C A M plants
0%
All of the above

Explanation

The most distinct feature is presence of bundle sheath with chloroplasts in the leaves. It is like a wreath around the vascular bundle. Hence, such anatomy is called as 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 mestome sheath. Mesophyll cell chloroplasts are granal and starch lacking but the bundle sheath cell chloroplasts are grana - lacking and starch - rich. Such feature is known as chloroplast dimorphism. Dimorphism of chloroplast is found in C

$_{4}$ plants and absent in

$C_{3}$ and CAM plants. Thus, option A is correct and other options are incorrect.

The cells of bundle sheath of

${C_4}$ plants are also known as

0%
Sheath-cells
0%
Slack-cells
0%
Kranz
0%
All of the above

Explanation

Bundle sheath cells are a layer of cells in plant leaves and stems, that forms a sheath surrounding the vascular bundles. In

$C_4$ plants the bundle sheath cells contain chloroplasts and are the site of the Calvin cycle. The initial fixation of carbon dioxide to form malic acid takes place in the palisade mesophyll cells, which in

$C_4$ plants form a circle around the bundle sheath. This arrangement, known as Kranz anatomy or structure (after the German Kranz, wreath), ensures that the palisade cells are in close contact with the bundle sheath cells, so that the malic acid can easily pass to the bundle sheath. It also means that the products of photosynthesis can be quickly transferred from the bundle sheath to the adjacent phloem tissue for transport to other parts of the plant. Thus, option C is correct and other options are incorrect.

Photosynthesis in

${C_4}$ plants is relatively less limited by atmospheric

${C O_2}$ levels, because

0%
Four carbon acids are the primary initial ${C O_2}$ fixation products
0%
The primary fixation of ${C O_2}$ is mediated via PEP carboxylase
0%
Effective pumping of ${C O_2}$ into bundle sheath cells
0%
Rubisco in ${C_4}$ plants has higher affinity for ${C O_2}$

Explanation

Photosynthesis in

$C_4$ plants is relatively less limited by atmospheric

$CO_2$ levels, because the primary fixation of

$CO_2$ is mediated via PEP carboxylase. At relatively low concentrations of

$CO_2$ , most

$CO_2$ will be fixed by PEP carboxylase.

$C_4$ pathway uses more energy than

$C_3$ pathway.

So, the correct answer is option B.

The process of photorespiration in

${C_3}$ plants starts from

0%
Phosphoglycerate
0%
Phosphoglycolate
0%
Glycerate
0%
Glycine

Explanation

The process of photorespiration in C3 plants takes place in the presence of excess

$O_2$ in the atmosphere. RUBISCO, the main enzyme of Calvin cycle that fixes

$CO_2$ acts as ribulose bis-phosphate oxygenase under the low atmospheric concentration of

$CO_2$ (below 1%) and increased concentration of

$O_2$ . In the presence of high concentration of

$O_2$ , the enzyme RuBP oxygenase splits a molecule of ribulose-1,5-bisphosphate into one molecule each of 3-phosphoglyceric acid and 2-phosphoglycolate which is the first step of the process.

Thus, the correct answer is option B.

Plants like sugarcane and sorghum have indigenously developed system to overcome the loss by photorespiration as they are ......... plants.

0%
${C_4}$
0%
${C_3}$
0%
${C_2}$
0%
${C_1}$

In case of

${C_4}$ pathway,

${C O_2}$ combines with

0%
PGA
0%
PEP
0%
RDP
0%
RMP

Explanation

In C

$_4$ plants, PEP carboxylase fixes PEP with carbon dioxide in the mesophyll cells of the leaf and results in four carbon compound, malate which is shuttled into the bundle sheath cells. Thus, option B is correct.
PGA, RDP, RMP are the intermediate products of C

$_3$ pathway.

Therefore, the correct answer is option B.

Pick up

${C_4}$ plant

0%
Papaya
0%
Potato
0%
Maize
0%
Pea

Explanation

C $_4$ carbon fixation is one of three biochemical mechanisms, along with C $_3$ and CAM photosynthesis, used in carbon fixation.
It is named for the 4-carbon molecule present in the first product of carbon fixation in the small subset of plants known as C $_4$ plants, in contrast to the 3-carbon molecule products in C $_3$ plants. Examples of C $_4$ plants include the food crops maize, sugar cane, millet, and sorghum. Thus, option C is correct.

Potato and papaya are C

$_3$ plants. Pea is a C

$_2$ plant.

During photorespiration the number of glycine molecules giving rise to one molecule of

${CO_2}$ are

0%
2
0%
1
0%
4
0%
3

Explanation

Photorespiration (also known as the oxidative photosynthetic carbon cycle, or C2 photosynthesis) is a process in plant metabolism which attempts to reduce the consequences of a wasteful oxygenation reaction by the enzyme RuBisCO. The desired reaction is the addition of carbon dioxide to RuBP (carboxylation), a key step in the Calvin Benson cycle, however approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (oxygenation), producing a product that cannot be used within the CalvinBenson cycle. The conversion of 2x 2 carbon glycine to 1 C3 serine in the mitochondria by the enzyme glycine-decarboxylase is a key step, which releases CO

$_{2}$ , NH

$_{3}$ 3, and reduces NAD to NADH.Thus, during photo respiration the number of glycine molecules giving rise to one molecule of CO

$_{2}$ are 2. So, option A is correct and other options are incorrect.

In noncyclic photophosphorylation, PS I is reduced by:

0%
Electron from ferredoxins
0%
Electron from PS II
0%
Hydrogen from PS II
0%
Hydrogen from water

Explanation

In noncyclic photophosphorylation, PS I is reduced by an electron from PS II. When light excites P-

${_6}$

${_8}$

${_0}$ it releases electrons and via intermediate electrons transporters it reaches PS I.

So, the correct answer is option B.

In non-cyclic photophosphorylation PS- I is reduced by

0%
Electrons from ferredoxin
0%
Electrons from PS- II
0%
Hydrogens from PS- II
0%
Hydrogens from water

${C_4}$ plants, the bundle sheath cells

0%
Have thin walls to facilitate gaseous exchange.
0%
Have large intercellular spaces.
0%
Are rich in PEP carboxylase.
0%
Have a high density of chloroplasts.

Explanation

$C_4$ plants, the bundle sheath cells have thicker walls and have no inter cellular spaces. These cells are not rich in PEP carboxylase. Bundle sheath cells have high density of chloroplasts compared to mesophyll cells. Thus, option D is correct and other options are incorrect

So, the correct answer is 'Have a high density of chloroplasts'

Identify the incorrect statement with respect to Calvin cycle.

0%
The carboxylation of RUBP is catalysed by RuBisCo.
0%
During the fixation, intermediate compound is formed by phosphoglycolate.
0%
18 molecules of ATP are synthesized during carbon fixation.
0%
NADPH + ${H^+}$ produced in light reaction is used to reduce diphosphoglycerate.

Explanation

Calvin cycle or the dark reaction is the incorporation of CO

$_2$ into carbohydrate.

It consists of three steps:-

Carboxylation: The CO $_2$ is accepted by RuBP by the formation of the covalent bond and the enzyme catalyzing the reaction is RuBP carboxylase oxygenase.
Reduction: These are the series of reactions that lead to the formation of glucose. it involves utilization of 2 ATP for phosphorylation and two NADPH for reduction per CO $_2$ molecule fixed and the fixation requires six turns of the cycle so 18 ATP and 12 NADPH are used.
Regeneration: RuBP regenerates and requires a molecule ATP for phosphorylation to form it.

So the correct option is '18 molecules of ATP are synthesized during carbon fixation.'.

${C_4}$ plants, the primary

${CO_2}$ acceptor is

0%
3-PGA
0%
Oxalo acetic acid
0%
RUBP
0%
PEP

Explanation

$C_4$ pathway, first step is the carboxylation of PEP, which leads to production of oxaloacetic acid. Thus, in

$C_4$ plants, the primary

$CO_2$ acceptor is PEP. Thus, option D is correct.
Oxaloacetic acid and 3-PGA are the intermediate products of

$C_4$ cycle. Thus, option A and B are wrong.

Which enzyme fixes

${CO_2}$ in Calvin cycle?

0%
RUBP carboxylase
0%
PEP carboxylase
0%
Carbonic anhydrase
0%
Hexokinase

Explanation

The Calvin cycle is a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of

$CO_2$ and leaves in the form of sugar.

$CO_2$ in Calvin cycle is fixed by the enzyme RUBP carboxylase. Thus, option A is correct.
PEP carboxylase, carbonic anhydrase and hexokinase can not fix

$CO_2$ in Calvin cycle, as these enzymes are not involved in Calvin cycle.

Thus, the correct answer is option A.

${C_4}$ plants are more efficient in photosynthesis than

${C_3}$ plants due to

0%
Lower rate of photorespiration.
0%
Higher leaf area.
0%
Presence of larger number of chloroplasts in the leaf cells.
0%
Presence of thin cuticle.

Explanation

$C_3$ plants,

$CO_2$ is pumped directly into the Calvin cycle, leaving rubisco exposed to

$O_2$ . Rubisco in a

$C_3$ will take up

$O_2$ rather than

$CO_2$ to undergo photorespiration. Photorespiration occurs under low concentrations of

$CO_2$ and high concentrations of

$O_2$ . This process reduces efficiency of photosynthesis, potentially reducing photosynthetic output by 25% in

$C_3$ plants.

$C_4$ plants capture carbon dioxide in their mesophyll cells forming oxaloacetate. This oxaloacetate is then converted to malate and is transported into the bundle sheath cells, where oxygen concentration is low to avoid photorespiration. So,

$C_4$ plants are more efficient in photosynthesis than

$C_3$ plants. Thus, option A is correct.

Photorespiration and photosynthesis both require

0%
Organic fuel
0%
Chlorophyll
0%
Cytochromes
0%
Energy

The mechanism of ATP formation in chloroplast is explained by:

0%
Relay pump theory of Godlewski
0%
Cholodny-Went's model
0%
Chemiosmotic theory
0%
Munch's pressure/ mass flow model

Photorespiration is favoured by

0%
Low temperatures
0%
Low light intensity
0%
High ${O_2}$ and low ${CO_2}$
0%
Low ${O_2}$ and high ${CO_2}$

Explanation

Solution:

Correct answer is option C
Explanation for correct option:

Photorespiration occurs when the ${CO_2}$ levels inside a leaf become low. 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 will increase relative to ${CO_2}$ concentrations.
When the ${CO_2}$ levels inside the leaf drop to around 50 ppm, Rubisco starts to combine O $_{2}$ with RuBP instead of ${CO_2}$ .
The net result of this is that instead of producing 2 3C PGA molecules, only one molecule of PGA is produced and a toxic 2C molecule called phosphoglycolate is produced. Thus, photorespiration is favoured by high O $_{2}$ and low ${CO_2}$ .

Which of the following is not paired correctly?

0%
Krebs - Tricarboxylic acid cycle
0%
Koshland - Induced fit theory
0%
Mitchell - Noncyclic photophosphorylation
0%
Singer and Nicholson - Fluid mosaic model

Which one of the following statements about the events of noncyclic photophosphorylation is incorrect?

0%
Photolysis of water takes place
0%
${O_2}$ is released
0%
Only one photosystem participates
0%
ATP and NADPH are produced

Explanation

Photosystem II has P680 reaction center wherein oxygen atoms of two water molecules bind to a cluster of manganese atoms. These Mn atoms are associated with an enzyme that splits water, removes electrons one at a time. Immediately after removal of four electrons from the two water molecules, O2 is released. Sunlight driven splitting of water is called as photolysis. Noncyclic photophosphorylation includes the flow of electron from PSII through quinone, cyt

$b_6$ f complex and plastocyanin to NADPH via PSI. NADP reductase enzyme is located on the stromal side of PSI and catalyzes the reduction of NADP into NADPH. Both PSI and PSII are involved; absence of PSII leads to cyclic photophosphorylation. Splitting of water and flow of electron through cytochrome

$b_6$ f complex add protons to thylakoid lumen. These protons are moved back to stroma through proton channels of ATP synthesis drives the synthesis of ATP. Thus, the correct answer is option C.

Which of the following is formed during photorespiration?

0%
Sugar
0%
Phosphoglycolate
0%
NADPH
0%
ATP
0%
Oxaloacetate

Explanation

Photorespiration occurs when the

$CO_2$ levels inside a leaf become low. 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 will increase relative to

$CO_2$ concentrations. When the

$CO_2$ levels inside the leaf drop to around 50 ppm, Rubisco starts to combine

$O_2$ with RuBP instead of

$CO_2$ . The net result of this is that instead of producing 2 3C PGA molecules, only one molecule of PGA is produced and a toxic 2C molecule called phosphoglycolate is produced. Thus, option B is correct.

Who amongst the following, first observed photosynthesis in plants?

0%
Melvin Calvin
0%
Darwin
0%
Arnon
0%
R. Hill

Which of the following statements is true with regard to the light reaction of photosynthesis?

0%
In PSII the reaction center chlorophyll a has an absorption peak at 700 nm, hence is called P 700
0%
In PSI the reaction center chlorophyll has an absorption maxima at 680 nm and is called P 680
0%
The splitting of water molecules is associated with PSI
0%
Photosystems I and II are involved in Z scheme
0%
Lamellae of the grana have PSI and PS II and stroma lamellae membranes have PS II only

The bundle sheath cells of

${C_4}$ plants having Kranz anatomy possess

0%
Thin walls, no intercellular spaces and several granal chloroplasts.
0%
Thick walls, many intercellular spaces and few chloroplasts.
0%
Thin walls, many intercellular spaces and no chloroplasts.
0%
Thick walls, no intercellular spaces and large number of agranal chloroplasts.

Explanation

Kranz anatomy is a special structure in the leaves of plants that have a

$C_4$ pathway of carbon dioxide fixation. The leaves contain a ring of mesophyll cells, containing a few small chloroplasts concerned with the initial fixing of carbon dioxide, surrounding a sheath of parenchyma cells (the bundle sheath) which has large chloroplasts involved in the Calvin cycle. Bundle sheath cells, contains starch-rich chloroplasts (agranal) lacking grana in a large amount. These bundle sheath cells have no inter cellular spaces. Thus, option D is correct and other options are incorrect.

PGA as the first

${CO_2}$ fixation product was discovered in photosynthesis of

0%
Algae
0%
Bryophyte
0%
Gymnosperm
0%
Angiosperm

The path of

$CO_2$ in the dark reactions of photosynthesis was successfully traced by the use of which of the following?

0%
$O^{18}$
0%
$C^{14}$
0%
$O^{32}$
0%
X-rays

Explanation

$C^{14}$ is a radioisotope of carbon and has been used extensively in photosynthesis research. By following this isotope, various intermediates of Calvin cycle were worked out and 3-phosphoglyceric acid was established as the first stable product of the dark reaction. Calvin and coworker used the technique of chromatography on cell extracts of alga, Chlorella and Scenedesmus to ascertain the

$C_3$ cycle intermediates after exposing these algae to

$C^{14}$ isotope.

Fill in the correct sets in the given pathway at A, B and C. In which of the following options correct words for all the three blanks A, B and C are indicated?

0%
A - Decarboxylation, B - Reduction, C - Regeneration
0%
A - Fixation, B - Transamination, C - Regeneration
0%
A - Carboxylation, B - Decarboxylation, C - Reduction
0%
A - Fixation, B - Decarboxylation, C - Regeneration

Explanation

The given picture denotes

$C_4$ cycle, which is also known as Hatch and Slack pathway. In the given pathway:
A denotes 'fixation'.
B denotes 'decarboxylation'.
C denotes 'regeneration'.
The

$CO_2$ acceptor in

$C_4$ plants in phosphoenolpyruvate (PEP). PEP reacts with

$CO_2$ to form oxaloacetic acid, which is reduced by NADPH to form malic acid. The malic acid then reacts with RUBP to form pyruvic acid and PGA. The pyruvic acid is then phosphorylated by ATP to regenerate PEP while PGA is converted to triose phosphate as far as

$C_3$ plants. These reactions are called as the Hatch and Slack pathway.

The site of Calvin cycle is

0%
Chloroplast
0%
Cytoplasm
0%
Mitochondria
0%
Glyoxysomes

Which one of the following is concerned with photophosphorylation?

0%
ADP + AMP $\xrightarrow{Lightenergy}$ ATP
0%
ADP + Inorganic $PO_{4}$ $\xrightarrow{Lightenergy}$ ATP
0%
ADP + Inorganic $PO_{4}$ $\rightarrow$ ATP
0%
AMP + Inorganic $PO_{4}$ $\rightarrow$ ATP

In photosynthesis

$CO_2$ combines with

0%
RUDP or RUBP
0%
ATP
0%
ADP
0%
PGA

$NADPH_{2}$ is also called as

0%
Real power
0%
Oxidising agent
0%
Power house of energy
0%
Reducing power

Explanation

The

$NADPH_2$ is synthesized in non-cyclic photophosphorylation in the light phase of photosynthesis. This is used subsequently in the dark phase to reduce carbon dioxide into sugars.

$NADPH_2$ is also called as reducing power. The substance provides the hydrogen molecules to perform reduction of the other substance.

Thus, the correct answer is option D.

During the dark reactions of photosynthesis

0%
Water splits.
0%
$CO_2$ is reduced to organic compounds.
0%
Chlorophyll is activated.
0%
Six carbon sugar is broken into three carbon sugar.

Explanation

Photosynthesis occurs in two phases-light reaction and dark reaction. During light reaction water undergoes photolysis releasing oxygen and reduced

$NADPH_2$ and ATP molecules are synthesized. During the dark reaction,

$NADPH_2$ and ATP are used to reduce carbon dioxide into sugars.

The function of ATP in photosynthesis is the transfer of energy from the

0%
Dark reaction to the light reaction
0%
Light reaction to the dark reaction
0%
Chloroplasts to mitochondria
0%
Mitochondria to chloroplasts

Explanation

$ATP$ can be used to store energy for future reactions or be withdrawn to pay for reactions when energy is required by the cell.
Likewise, plants capture and store the energy they derive from light during photosynthesis in $ATP$ molecules along with $NADPH + H^+$ .
These products are used subsequently to reduce carbon dioxide into sugars during dark reaction.
Thus, the purpose of ATP in photosynthesis is to transfer energy from light reaction to dark reaction.

So, the correct answer is option B.

Algae and other submerged plants float in water during day time and sink at night, because

0%
They become light due to food material accumulation.
0%
They lose weight at night.
0%
They become bouyant due to accumulation of $O_{2}$ as a result of photosynthesis.
0%
None of the above.

During photosynthesis

0%
Water is reduced and $CO_2$ is oxidized.
0%
$CO_2$ is reduced and water is oxidized.
0%
Both $CO_2$ and water get reduced.
0%
Both $CO_2$ and water get oxidized.

Connecting link between light phase and dark phase of photosynthesis is

0%
Only $ATP$
0%
Only $NADH_2$
0%
Only $NADPH_2$
0%
Both A and C

Explanation

Photosynthesis occurs in two stages- light reaction and dark reaction. During the light reaction,

$NADPH_2$ and ATP are synthesized. These products are used subsequently to reduce carbon dioxide into sugars. The purpose of ATP in photosynthesis is to transfer energy from light reaction to dark reaction. The purpose of NADP is to transfer hydrogen from light reaction to dark reaction in the form of reduced

$NADPH_2$ . Hence, ATP and reduced

$NADPH_2$ form the connecting link between light phase and dark phase of photosynthesis.

ADP + Pi = ATP in grana is called as

0%
Phosphorylation
0%
Oxidative phsphorylation
0%
Photophosphorylation
0%
Photolysis

During photosynthesis when PGA is changed into phosphoglyceraldehyde, which of the following reaction occur?

0%
Oxidation
0%
Reduction
0%
Electrolysis
0%
Hydrolysis

Tropical plants like sugarcane show high efficiency of

$CO_2$ fixation because of

0%
Calvin cycle
0%
Hatch - Slack cycle
0%
Cyclic photophosphorylation
0%
TCA Cycle

Explanation

Tropical plants like sugarcane and maize show

$C_4$ cycle or Hatch Slack pathway in which the carbon dioxide is initially fixed into four carbon atom containing organic acids. These plants do not show photorespiration and hence, show higher efficiency for carbon dioxide fixation as compared to the

$C_3$ plants.

Fixation of 1 CO

$_2$ requires

0%
6NADPH $_2$ and 3ATP
0%
2NADPH $_2$ and 3ATP
0%
4NADPH $_2$ and 3ATP
0%
5NADPH $_2$ and 3ATP

Explanation

The carbon dioxide acceptor in Calvin cycle is ribulose 1,5- bisphosphate and the first product is 3- phosphoglyceric acid. This conversion is catalyzed by the RUBISCO. Since the first stable product is a three carbon compound, it is called as

$C_3$ cycle. When 6 molecules of carbon dioxide enter Calvin cycle, one hexose molecule is formed. 18 ATP and 12

$NADPH_2$ molecules are used up. Thus, the ATP and

$NADPH_2$ consumed per carbon atom fixed in glucose are 3 ATP and 2

$NADPH_2$ .

Kranz type of anatomy is found in

0%
$C_4$ plant
0%
$C_3$ plant
0%
Succulents
0%
None of the above

Explanation

Word "Kranz" means a ring or wreath and refers to the thick walled bundle sheath cells present around vascular bundles in the shape of a ring in

$C_4$ plants. The bundle sheath cells have agranal chloroplast and fix carbon dioxide with the help of RuBisCO enzyme. The thin walled mesophyll cells carry out initial carbon dioxide fixation with the help of PEP carboxylase enzyme. This special arrangement of cells and presence of dimorphic chloroplasts helps in minimizing photorespiration in

$C_4$ plants.

The electron ejected by

$P_{680}$ in light reaction is initially accepted by

0%
Plastoquinone
0%
ATP
0%
Ferredoxin
0%
$P_{700}$

Explanation

During the light reaction, the path of the electron has been elucidated in the Z-scheme. It is named so because of its shape and was first proposed by Hill and Bendall in 1960. The electron released by reaction center of photosystem II i.e., P

${_6}$

${_8}$

${_0}$ moves uphill and reduces pheophytin, a nonmagnesium chlorophyll a molecule. From pheophytin, electrons are accepted by plastoquinone which requires two electrons for complete reduction. It also accepts two protons from the stromal side of thylakoid membrane and becomes reduced to

$PQH_2$ after accepting 2 electrons and 2 protons. It is the only carrier in the photosynthetic electron transport chain, which can bind both electrons and protons.

The enzyme that fixes atmospheric

$CO_2\, in\, C_4$ plants is

0%
PEP carboxylase
0%
Hexokinase
0%
RUBP oxygenase
0%
Hydrogenase

Explanation

The carbon dioxide is fixed during dark phase of photosynthesis using reducing and assimilatory power synthesized during light phase. The initial carboxylating enzyme is PEP carboxylase in

$C_4$ plants. It carboxylates PEP or phosphoenolpyruvate and produces organic acids having four carbon atoms.

Carbon dioxide acceptor in

$C_4$ plants is

0%
Phosphoenol pyruvic acid (PEP)
0%
Ribulose-1, 5- di phosphate
0%
NADP
0%
Ribulose-5 - phosphate

Explanation

$C_4$ plants fix atmospheric carbon dioxide into four carbon compounds oxaloacetic acid or malic acid. The initial carboxylation is brought about by the enzyme PEP carboxylase, which carboxylates phosphoenol pyruvic acid (PEP) into four carbon compounds.

CBSE Questions for Class 11 Medical Biology Photosynthesis In Higher Plants Quiz 4 - 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 4 - MCQExams.com

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Practice Class 11 Medical Biology Quiz Questions and Answers

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