Photosynthesis in Higher Plants Test

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Photosynthesis in Higher Plants Test - 78

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Question 1
1 / -0

Chemical reaction that takes place during the dark reaction of photosynthesis is called as

A
Photolysis.

B
Hydrolysis.

C
Binding of carbon dioxide with RUBP.

D
Nitrogen fixation.

Solution

The light-independent reactions of photosynthesis are chemical reactions that convert carbon dioxide and other compounds into glucose. These reactions occur in the stroma of the chloroplast. There are three phases to the light-independent reactions, collectively called the Calvin cycle: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration.
Question 2
1 / -0

Extrachromosomal DNA is present in the

A
Nucleus.

B
Glyoxysome.

C
Ribosome.

D
Chloroplast.

Solution

The nucleus is a double membrane-bound organelle containing chromosomes which in turn carry DNA molecules. DNA present in the nucleus is called nuclear/chromosomal DNA. The DNA molecules which are present anywhere in the cell, other than nuclear chromosomes, is called as extranuclear or extrachromosomal DNA. Glyoxysomes are membrane-bounded organelles, the specialized peroxisomes, which carry the enzymes of the glyoxylate cycle. They are present in lipid-rich seeds during germination, and disappear after the developing plant acquires the ability to carry out photosynthesis. They do not have DNA. Ribosomes are the large cytoplasmic complexes of rRNA and a set of protein and serve as the site for protein synthesis; DNA is not present in ribosomes. The chloroplast is double membrane-bound semi-autonomous organelles that harvest the sunlight to produce ATP and carbohydrates. They have double-stranded circular DNA molecules.
Question 3
1 / -0

The number of ATP required in excess to assimilate atmospheric $CO_2$ to four molecules of triose phosphates in $C_4$ plants as compared to $C_3$ plants is

A
30

B
36

C
60

D
8

Solution

For one glucose molecule, 6 turns of C $_3$ cycle are required for producing 12 molecules of triose, out of which 2 will be used for glucose. For 6 cycles, 18 ATP are required. ATP produced in one cycle is 18/6=3. If there are 4 molecules required for glucose formation, 4 cycles should take place. So, 3 x 4 = 12 ATP required for 4 molecules of triose.
Similarly, for one glucose molecule, 6 turns of C $_4$ cycle are required for producing 12 molecules of triose, out of which 2 will be used for glucose. For 6 cycles, 30 ATP are required. ATP produced in one cycle is 30/6=5. If there are 4 molecules required for glucose formation, 4 cycles should take place. So, 5 x 4 = 20 ATP required for 4 molecules of triose.
So, there are 20-12 = 8 molecules of ATP required in excess.
Thus, the correct answer is option D.
Question 4
1 / -0

Which of the following processes is responsible for the release of oxygen?
I. Lactic acid fermentation
II. Alcohol fermentation
III. Aerobic respiration
IV. Photosynthesis

A
I and II

B
I and III

C
II only

D
IV only

E
III and IV

Solution

Aerobic respiration is the breakdown of sugar/other food substances in the presence of oxygen to release energy. It includes glycolysis, Krebs cycle and electron transport chain. Glycolysis and Kreb cycle produce reducing compounds NADH, FADH $_2$ which are then oxidized in the presence of oxygen by the process of chemiosmosis and reduce oxygen to water. Fermentation is incomplete oxidation of food substances into alcohol and lactic acid with a small amount of energy being released. Both lactic acid and ethanol fermentation do not produce oxygen. Photosynthesis is the fixation of atmospheric carbon dioxide into organic compounds; use of water as the electron donor by photoautotrophs during photophosphorylation results in the production of oxygen.
Therefore, the correct answer is option D.
Question 5
1 / -0

Which one does not differ between a C3 and a C4 plant?
(I) Initial CO ${_2}$ acceptor.
(II) Extent of photorespiration.
(III) Enzyme catalyzing reaction that fixes CO ${_2}$ .
(IV) Presence of Calvin cycle.
(V) Leaf anatomy.

A
I and V

B
IV

C
II and III

D
II

Solution

The initial Co2 receptor is RuBP for c3 plants whereas phosphoenolpyruvate for C $_4$ plants. Photorespiration losses are high in C $_3$ whereas low in C $_4$ . Calvin cycle is a dark reaction which occurs in both C $_3$ and C $_4$ plants. C $_4$ plants have specialized karnz anatomy of leaves. Thus, the correct answer is option B.
Question 6
1 / -0

In the ${C}_{4}$ pathway, the $C{O}_{2}$ fixation in mesophyll cells is carried out by the enzyme

A
Pyruvate dehydrogenase.

B
Pyruvate decarboxylase.

C
PEP carboxylase.

D
Rubisco.

Solution

The details of the $C_4$ cycle: after entering through stomata, $CO_2$ diffuses into a mesophyll cell. Being close to the leaf surface, these cells are exposed to high levels of $O_2$ , but have no RUBISCO so cannot start photorespiration (nor the dark reactions of the Calvin cycle). Instead, the $CO_2$ is inserted into a 3-carbon compound ( $C_3$ ) called phosphoenolpyruvic acid (PEP) forming the 4-carbon compound oxaloacetic acid ( $C_4$ ). Oxaloacetic acid is converted into malic acid or aspartic acid (both have 4 carbons), which is transported (by plasmodesmata) into a bundle sheath cell. Bundle sheath cells are deep in the leaf so atmospheric oxygen cannot diffuse easily to them; often have thylakoids with reduced photosystem II complexes (the one that produces $O_2$ ). Both of these features keep oxygen levels low. Here the 4-carbon compound is broken down into carbon dioxide, which enters the Calvin cycle to form sugars and starch. Pyruvic acid ( $C_3$ ), is transported back to a mesophyll cell where it is converted back into PEP.
Question 7
1 / -0

Identify the correct statement(s) in relation to $C_4$ photosynthesis.

A
Kranz anatomy is an essential feature for $C_4$ plants.

B
$C_4$ plants have higher water use efficiency than $C_3$ plants.

C
Photorespiration can be minimized when $C_4$ pathway is in operation.

D
All of the above.

Solution

Kranz leaf anatomy refers to the presence of two photosynthetic cell types namely bundle sheath (BS) cells and mesophyll (M) cells and is the characteristic of $C_4$ plants. 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. These plants can carry out photosynthesis even keeping the stomata closed and exhibit high water use efficiency. OAA is converted into malate in mesophyll cells. Thus, the correct answer is option D.
Question 8
1 / -0

In non-cyclic electron transport system, the path of electron is

A
$PS-I\rightarrow PS-II\rightarrow NADP$

B
$PS-II\rightarrow PS-I\rightarrow NADP$

C
$NADP\rightarrow PS-II\rightarrow PS-I$

D
$NADP\rightarrow PS-I\rightarrow PS-II$
Solution
- Photosystem II has P $_{680}$ reaction centre 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.
- After the removal of four electrons from the two water molecules, O $_2$ is released. Sunlight-driven splitting of water is called as photolysis.
- Noncyclic photophosphorylation includes the flow of electron from PSII through quinone, cytochrome b6-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.
- Splitting of water and flow of electron through cytochrome b6-f complex add protons to thylakoid lumen.
- These protons are transported which drives the synthesis of ATP.
Thus, the correct answer is option B.
Question 9
1 / -0

Statement A: Photorespiration decreases photosynthesis output.
Statement B: In photorespiratory pathway, neither ATP nor NADPH is produced.

A
Both the statements A and B are correct.

B
Both the statements A and B are wrong.

C
Statement A is correct and Statement B is wrong.

D
Statement B is correct and statement A is wrong.

Solution

Photorespiration is a cyclic process in which the enzyme Rubisco acts as an oxygenase enzyme instead of carboxylase enzyme. The active site of this enzyme is same for both of these activities. In C3 plants, some O2 always binds to Rubisco.
Photorespiration does not produce energy or reducing power, rather it consumes energy.
Thus, the correct answer is option A.
Question 10
1 / -0

Chemiosmosis, the generation of a proton gradient across the inner mitochondrial membrane, is a crucial requirement for the synthesis of ATP in cellular respiration.

How does the cell power the movement of protons up its gradient?

A
A transporter on the outer membrane allows the diffusion of protons from the cytoplasm into the inner membrane space.

B
ATP synthase powers the movement of protons across the membrane while simultaneously generating ATP.

C
Electrons are transported into the inner membrane space drawing in protons due to electrostatic attraction.

D
Complexes of the electron transport chain undergo redox reactions that, in turn, generates the energy to pass protons up its gradient.

Solution

The protein complexes of the electron transport chain accept and pass on e $^-$ to the next acceptor, that is they undergo redox reactions, during this process the e $^-$ moves down its energy gradient releasing free energy at each transfer, also called as EMF which drives the movement of protons up their concentration gradient into the matrix of mitochondria
So, the correct answer is 'Complexes of the electron transport chain undergo redox reactions that, in turn, generates the energy to pass protons up its gradient'

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Photosynthesis in Higher Plants Test - 78

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Photosynthesis in Higher Plants Test - 78

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SHARING IS CARING

Question 1

Photolysis.

Hydrolysis.

Binding of carbon dioxide with RUBP.

Nitrogen fixation.

Solution

Question 2

Nucleus.

Glyoxysome.

Ribosome.

Chloroplast.

Solution

Question 3

30

36

60

8

Solution

Question 4

I and II

I and III

II only

IV only

III and IV

Solution

Question 5

I and V

IV

II and III

II

Solution

Question 6

Pyruvate dehydrogenase.

Pyruvate decarboxylase.

PEP carboxylase.

Rubisco.

Solution

Question 7

Kranz anatomy is an essential feature for C4C_4C4​ plants.

C4C_4C4​ plants have higher water use efficiency than C3C_3C3​ plants.

Photorespiration can be minimized when C4C_4C4​ pathway is in operation.

All of the above.

Solution

Question 8

PS−I→PS−II→NADPPS-I\rightarrow PS-II\rightarrow NADPPS−I→PS−II→NADP

PS−II→PS−I→NADPPS-II\rightarrow PS-I\rightarrow NADPPS−II→PS−I→NADP

NADP→PS−II→PS−INADP\rightarrow PS-II\rightarrow PS-INADP→PS−II→PS−I

NADP→PS−I→PS−IINADP\rightarrow PS-I\rightarrow PS-IINADP→PS−I→PS−II

Solution

Question 9

Both the statements A and B are correct.

Both the statements A and B are wrong.

Statement A is correct and Statement B is wrong.

Statement B is correct and statement A is wrong.

Solution

Question 10

A transporter on the outer membrane allows the diffusion of protons from the cytoplasm into the inner membrane space.

ATP synthase powers the movement of protons across the membrane while simultaneously generating ATP.

Electrons are transported into the inner membrane space drawing in protons due to electrostatic attraction.

Complexes of the electron transport chain undergo redox reactions that, in turn, generates the energy to pass protons up its gradient.

Solution

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Kranz anatomy is an essential feature for $C_4$ plants.

$C_4$ plants have higher water use efficiency than $C_3$ plants.

Photorespiration can be minimized when $C_4$ pathway is in operation.

$PS-I\rightarrow PS-II\rightarrow NADP$

$PS-II\rightarrow PS-I\rightarrow NADP$

$NADP\rightarrow PS-II\rightarrow PS-I$

$NADP\rightarrow PS-I\rightarrow PS-II$