Photosynthesis in Higher Plants Test

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Photosynthesis in Higher Plants Test - 51

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Question 1
1 / -0

$$C_4$$ plants are photosynthetically more efficient than $$C_3$$ plants because

A
$$CO_2$$ efflux is not prevented

B
They are able to avoid photorespiration

C
$$CO_2$$ compensation point is more

D
$$CO_2$$ generated during photorespiration is recycled through PEP carboxylase.
Solution
Correct Option: B
Explanation:
In the Calvin cycle or $${C_3}$$, 18 molecules of ATP and 12 molecules are NADPH is required for the formation of each molecule of glucose.
The overall equation of $${C_3}$$ carbon assimilation is as follows:
$$6C{O_2} + 6RuBP + 18ATP + 12NADPH \to {C_6}{H_{12}}{O_6} + 6RuBP + 18ADP + 18Pi({H_3}P{O_4}) + 12NAD{P^ + }$$
$${C_4}$$ plants are adapted to overcome photorespiration and deliver carbon dioxide directly to the enzyme.
$${C_3}$$ plants lose more than half of the photosynthetically fixed carbon dioxide by photorespiration.
The overall reaction for $${C_4}$$ pathway is as follows:

$$6PEP + 6RuBP + 6C{O_2} + 30ATP + 12NADPH \to 6PEP + 6RuBP + {C_6}{H_{12}}{O_6} + 30ADP + 30{H_3}P{O_4} + 12NAD{P^ + }$$
Hence, $${C_4}$$ plants are photosynthetically more efficient than $${C_3}$$ plants because they are able to avoid photorespiration.
Question 2
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Which of the following is an essential component of chlorophyll?

A
Mn

B
Cu

C
Mg

D
Fe

Solution

A) Manganese plays a minor role in maintaining the structure of the choloplast.
B) Copper is required for photosynthesis in chloroplasts because it is a cofactor of plastocyanin, an essential electron carrier in the thylakoid lumen.
C) Magnesium is the central atom in the chlorophyll molecule and is structurally very important. Hence, it is the most essential component of chlorophyll.
D) Iron takes part in electron transport during photosynthesis.
So the correct answer is 'Mg'.
Question 3
1 / -0

Molecules of RuBP required to produce 20 molecules of serine in photorespiration are

A
60

B
40

C
20

D
80

Solution

1 mol. of RuBP in the presence of O$$_2$$ splits into 1 mol. of 2-phosphoglycolic acid and 1 mol. of 3 PGA.
1 mol. of Phosphoglycolic acid is converted to 1 mol into glycolic acid which oxidized to 1 mol. of glyoxylic acid.
1 mol. of glyoxylic acid by transamination form 1 mol. of glycine.
2 mol. of glycine in peroxisome form 1 mol. of serine.
Therefore, 2 mol. of RuBP require to form 1 mol. of serine so 40 mol. require to form 20 mol. of serine.
Hence, the correct answer is '40'.
Question 4
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$$NAD^+$$ is reduced in photorespiration inside

A
Mitochondria

B
Mitochondria and peroxisome

C
Mitochondria and chloroplasts

D
Chloroplasts and peroxisomes.

Solution

In photorespiration, the glycine is transported out of peroxisomes into mitochondria, where two molecules of glycine interact to form one molecule each of serine, CO$$_2$$, NH$$_3$$.

2 Glycine + H$$_2$$O + NAD$$^+\rightarrow$$ Serine + CO$$_2$$+ NH$$_3$$ + NADH
When glyceric acid finally enters the chloroplast where it is phosphorylated to 3 PGA which enters in C$$_3$$ cycle, where during the reduction process, NAD$$^+$$ is reduced.
Hence, the correct answer is 'Mitochondria and chloroplasts'.
Question 5
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In photorespiration, peroxisome helps in

A
Synthesis of PGA

B
Reduction of glyoxylate

C
Oxidation of glycolate

D
Oxygenation of glycolate

Solution

The most prominent role of peroxisomes in photosynthetic plant tissues is their participation in photorespiration, a process also known as the oxidative C2 cycle or the oxidative photosynthetic carbon cycle. Photorespiration is an essential process in land plants, as evident from the conditionally lethal phenotype of mutants deficient in enzymes or transport proteins involved in this pathway. The oxidative C2 cycle is a salvage pathway for phosphoglycolate, the product of the oxygenase activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO), to the Calvin cycle intermediate phosphoglycerate. The pathway is highly compartmentalized and involves reactions in chloroplasts, peroxisomes, and mitochondria.

So, the correct option is 'Oxidation of glycolate'.
Question 6
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Which of the following statements regarding C$$_4$$ plants is false?

A
The primary CO$$_2$$ acceptor is a 5-carbon molecule.

B
The initial carboxylation reaction occurs in mesophyll.

C
Calvin pathway does not take place in the mesophyll cells but does so only in bundle sheath cells.

D
Leaves that fix CO$$_2$$ have two cell types.

Solution

A) The primary carbon dioxide acceptor is PEP carboxylase which is a 5-carbon molecule.
B) Initial carboxylation reaction occurs in the bundle sheath cell.
C) Fixation of carbon dioxide by Calvin's cycle takes place in the bundle sheath cells.
D) Leaves of $${ C }_{ 4 }$$ plants have Kranz anatomy and have two types of cells- bundle sheath cells and mesophyll cells. They fix carbon dioxide.
So the correct option is 'The initial carboxylation reaction occurs in mesophyll'.
Question 7
1 / -0

In which type of reactions related to plant photosynthesis, peroxisomes are involved?

A
Glycolytic cycle

B
Calvin cycle

C
Bacterial photosynthesis

D
Glyoxylate cycle

Solution

A) In the glycolytic cycle, glycolate is reduced to glyoxylate and $${ H }_{ 2 }{ O }_{ 2 }$$. This takes place in the peroxisome during photorespiration.
B) Peroxisomes are not involved in Calvin's cycle.
C) Oxygenic photosynthetic bacteria perform photosynthesis in a similar manner to plants. They contain light-harvesting pigments, absorb carbon dioxide, and release oxygen. So, peroxisomes are not involved.
D) Glyoxylate cycle is not directly involved in plant photosynthesis. It is mainly involved in electron transport.
So the correct answer is 'Glycolytic cycle'.
Question 8
1 / -0

Plants convert light into chemical energy with a photosynthetic efficiency of

A
35-41%

B
20-35%

C
6-20%

D
3-6%

Solution

A) Plants have a maximum photosynthetic efficiency of 10%, depending upon the plant. 35-41% efficiency is not possible.
B) An efficiency of 20-35% is not possible.
C) Plants do not exceed a photosynthetic efficiency of 10%
D) Most plants have a photosynthetic efficiency between 3-6%.
So the correct answer is '3-6%'.
Question 9
1 / -0

Which of the following statement is false about photosynthesis?

A
Enzymes required for carbon fixation are located in grana of chloroplasts.

B
In green plants, both PS I and PS II are required for synthesis of NADPH + H$$^+$$.

C
Electron carriers of photophosphorylation are located on thylakoid membranes.

D
Photosynthesis is a redox process in which water is oxidized and CO$$_2$$ is reduced.

Solution

A) Enzymes require for carbon fixation are present inside the mesophyll cells.
B) NADPH is synthesised during non-cyclic photophosphorylation which involves both PS I and PS II.
C) The electron carriers (cytochromes b and f) are present on the thylakoid membrane.
D) Carbon dioxide is fixed and reduced and water is oxidised into a proton and oxygen during photosynthesis.
So the correct answer is 'Enzymes required for carbon fixation are located in grana of chloroplasts.'
Question 10
1 / -0

Enzymes RuBP carboxylase-oxygenase and PEP carboxylase are activated by

A
Zn

B
Mo

C
Mn

D
Mg

Solution

A) Zn activates enzymes like carboxylases.
B) Mo is a component of enzymes like nitrogenase and nitrate reductase.
C) Mn is involved in the splitting of water to liberate oxygen.
D) Mg activates both RuBP carboxylase-oxygenase and PEP carboxylase.
So the correct answer is 'Mg'.

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Photosynthesis in Higher Plants Test - 51

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Photosynthesis in Higher Plants Test - 51

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Question 1

$$CO_2$$ efflux is not prevented

They are able to avoid photorespiration

$$CO_2$$ compensation point is more

$$CO_2$$ generated during photorespiration is recycled through PEP carboxylase.

Solution

Question 2

Mn

Cu

Mg

Fe

Solution

Question 3

60

40

20

80

Solution

Question 4

Mitochondria

Mitochondria and peroxisome

Mitochondria and chloroplasts

Chloroplasts and peroxisomes.

Solution

Question 5

Synthesis of PGA

Reduction of glyoxylate

Oxidation of glycolate

Oxygenation of glycolate

Solution

Question 6

The primary CO$$_2$$ acceptor is a 5-carbon molecule.

The initial carboxylation reaction occurs in mesophyll.

Calvin pathway does not take place in the mesophyll cells but does so only in bundle sheath cells.

Leaves that fix CO$$_2$$ have two cell types.

Solution

Question 7

Glycolytic cycle

Calvin cycle

Bacterial photosynthesis

Glyoxylate cycle

Solution

Question 8

35-41%

20-35%

6-20%

3-6%

Solution

Question 9

Enzymes required for carbon fixation are located in grana of chloroplasts.

In green plants, both PS I and PS II are required for synthesis of NADPH + H$$^+$$.

Electron carriers of photophosphorylation are located on thylakoid membranes.

Photosynthesis is a redox process in which water is oxidized and CO$$_2$$ is reduced.

Solution

Question 10

Zn

Mo

Mn

Mg

Solution

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