Tag: photosynthetic cycle

Questions Related to photosynthetic cycle

In CAM cycle, during the formation of malic acid, stomata remains

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. Open

  2. Closed

  3. Semi open

  4. Always closed

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Correct Option: A
Explanation:

CAM method 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. The carbon dioxide is then stored as a four-carbon acid, malate, and then used during photosynthesis during the day. The pre-collected CO2 is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency.

In maximum plants, stomata open during day and closed at night. Its exception is

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  1. Crassulacean acid metabolism plants

  2. $C _{3}$ plants

  3. $C _{4}$ plants

  4. None of the above

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Correct Option: A
Explanation:

Crassulacean acid metabolism 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. 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.

CAM helps the plants in

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  1. Reproduction

  2. Secondary growth

  3. Conserving water

  4. Disease resistance

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Correct Option: C
Explanation:
CAM stands for Crassulacean Acid Metabolism. Plants having CAM have scotoactive stomata. These plants fix $CO _{2}$ during the night but form sugars only during the day (when RuBisCO is active). CAM helps plants in conserving water. These plants are succulent and they have water-storing cells. Sedum, Kalanchoe, Opuntia, etc., are the examples of CAM plants.
So, the correct answer is 'Conserving water'

In overall photosynthetic pathway, for one molecule of $O _2$ liberated eight light quanta are required two molecules of NADPH$2$ are formed. Beside this, certain amount of energy is also released along with electron transport. This energy is liberated as.

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. $2$ ATP molecules

  2. $8$ ATP molecules

  3. $3$ ATP molecules

  4. $4$ ATP molecules

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Correct Option: A

$CO _{2} : NADPH _{2} : ATP$ ratio for $C _{4}$ plants is

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  1. $1 : 2 : 3$

  2. $2 : 3 : 4$

  3. $1 : 2 : 5$

  4. $1 : 5 : 10$

Show answer
Correct Option: C
Explanation:

In C$ _4$ pathway for production of one molecule of glucose we require 12 NADPH$ _2$, 30 ATP and 6CO$ _2$ are required.

CO$ _2$ : NADPH$ _2$ : ATP =  6 : 12 : 30

CO$ _2$ : NADPH$ _2$ : ATP =  1 : 2 : 5

Read the given statements and select the correct option. 
Statement 1 : Crassulacean acid metabolism occurs in succulent plants which grow in xeric conditions. 
Statement 2 : Stomata are generally sunken in succulent plants. 

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  1. Both statements are correct

  2. Statement 1 s correct but statement 2 is incorrect.

  3. Statement 1 is incorrect but statement 2 is correct.

  4. Both statement are incorrect.

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Correct Option: A
Explanation:

Crassulacean acid metabolism is a mechanism of photosynthesis involving double fixation of $CO _2$ which occurs in succulents belonging to Crassulaceae, Cacti, Euphorbias and some other plants of dry habitats. Here, the stomata remains closed during the daytime and opens only at night, e.g Sedum,Kalanchoe,Opuntia. Sunken stomata are deep seated stomata in which subsidiary cells lie above the guard cells.  So, the correct answer is 'Both statements are correct'.

Internal source of CO2 in CAM plants is

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. Oxaloacetic acid

  2. Malic acid

  3. RUBP

  4. PEPA

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Correct Option: A
Explanation:

In  CAM plant, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect CO$ _{2}$. This CO$ _{2}$ is fixed into oxaloacetate by PEP carboxylase, which is then converted to malate. The CO$ _{2}$ is stored as malate in vacuoles at night, and then in the daytime, it is transported to chloroplasts where it is converted back to CO$ _{2}$, which is then used during photosynthesis.  

So, the correct option is 'Oxalo acetic acid'.

In CAM plants, $ C{ O } _{ 2 } $ acceptor is

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. RuBP

  2. PEP

  3. OAA

  4. PGA

Show answer
Correct Option: B
Explanation:

Crassulacean Acid Metabolism (CAM) is a specialised photosynthetic process which is characterized by the following criteria given by  Osmond (1978) and Cluge and Tuge (1978). These are:

  1. CO$ _2$ uptake takes place mainly at night
  2. stomata are open during the night and closed during the day when CO$ _2$ uptake is mostly negligible.
  3. Malate accumulates at night by carboxylation of PEP.
  4. Decarboxylation of malate during the day yields CO$ _2$ which is fixed up by RuBP carboxylase. 
During the night time when the stomata are open, the CO$ _2$ is absorbed and fixed by phosphoenol pyruvic acid (PEP, 3C) in presence of enzyme PEP carboxylase. As a result of this PEP gets converted into oxaloacetic acid (OAA, 4C).
So the correct option is 'PEP'

In CAM plants the site of  light reaction and glucose synthesis are 

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. Mesophyll, Bundle seath

  2. Bundle sheath, Mesophyll

  3. Mesophyll, Mesophyll

  4. Bundle seath, Bundle seath

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Correct Option: B

Which of the following metabolic cycle is an adaptation against Glycolate metabolism?

botany photosynthesis cam cycle cam plants photosynthetic cycle

  1. Crassulacean acid metabolism

  2. Co-operative photosynthesis

  3. Reductive pentose phosphate pathway

  4. Photochemical reaction

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Correct Option: A