Engineering Questions with Answers - Multiple Choice Questions

MCQs on Chloroplast Function – CO2 Fixation and Carbohydrate Synthesis in CAM Plants

1 - Question

Which of the following plants undergo CAM photosynthesis?
a) Cactus
b) Sugarcane
c) Corn
d) Wheat

View Answer

Answer: a
Explanation: CAM is known as crassulacean acid metabolism. These CAM plants fix CO2 in the arid and hot climate regions.




2 - Question

The CAM pathway starts at daytime.
a) True
b) False

View Answer

Answer: b
Explanation: The CAM pathway starts at night when there is lower temperature. This is due to the mechanism that reduces water loss by evatranspiration.




3 - Question

Where is the malate stored in CAM plants?
a) Chloroplast
b) Mitochondria
c) Vacuoles
d) Endoplasmic reticulum

View Answer

Answer: c
Explanation: The CO2 is converted to malate, a four carbon organic compound. This is stored in the vacuoles where it is later transported to the chloroplast for conversion of malate to CO2 for photosynthesis.




4 - Question

. How many aquatic plant genera can undergo CAM photosynthesis?
a) 4
b) 5
c) 6
d) 7

View Answer

Answer: a
Explanation: The aquatic plants can also undergo CAM photosynthesis. There are about 4 genera of plants. They also follow the same pathway as the terrestrial CAM plants.




5 - Question

The CAM plants undergo daytime acidification and nighttime deacidification.
a) True
b) False

View Answer

Answer: b
Explanation: During the nighttime, the plants take up CO2 and convert it into organic acids called as acidification. While in daytime, they utilize the organic acids to form CO2 back known as deacidification.




6 - Question

Which enzyme is used in converting bicarbonate ion to oxaloacetate?
a) Phosphoenolpyruvate reductase
b) Phosphoenolpyruvate hydrogenase
c) Phosphoenolpyruvate carboxylase
d) Phosphoenolpyruvate dehydrogenase

View Answer

Answer: c
Explanation: The phosphoenolpyruvate carboxylase enzyme is used to catalyze bicarbonate to oxaloacetate and phosphate. This is one of the important mechanism in the carbon fixation in CAM plants.




7 - Question

Which enzyme is used to convert oxaloacetate to malate?
a) Malate dehydrogenase
b) Malate hydrolase
c) Malate carboxylase
d) Malate dehydratase

View Answer

Answer: a
Explanation: Oxaloacetate is converted to malate by the enzyme malate dehydrogenase. The oxaloacetate obtains an electron from NAD+ and converts it to a four carbon compound malate.




8 - Question

Which of the following is a facultative CAM plant?
a) Century plant
b) Corn
c) Maize
d) Common ice plant

View Answer

Answer: d
Explanation: Common ice plant is an facultative CAM plant. It usually does not undergo CAM photosynthesis but it undergoes CAM photosynthesis when it is under stress condition, like shortage of water, CO2, etc.




9 - Question

How many molecules of ATP and NADPH2 are used in synthesis of one glucose molecule?
a) 30 ATP and 10 NADPH2
b) 10 ATP and 30 NADPH2
c) 30 ATP and 12 NADPH2
d) 12 ATP and 30 NADPH2

View Answer

Answer: c
Explanation: The CAM pathway uses 30 ATP and 12 NADPH2 for synthesis of one glucose molecule. This is higher than the energy requirements of C4 and C3 cycles.

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