C4 Cycle

What is the key enzyme involved in the C4 cycle that fixes carbon dioxide in mesophyll cells?

• Phosphoenolpyruvate carboxylase (PEP carboxylase)

• Rubisco

• Pyruvate kinase

• ATP synthase

In which type of plants does the C4 cycle predominantly occur?

• Cacti

• Tropical grasses

• Desert plants

• Aquatic plants

What is the primary function of PEP carboxylase in C4 plants?

• Fix carbon dioxide into a 4-carbon compound

• Promote photosynthesis in C3 plants

• Regulate water uptake in the plant

• Convert 4-carbon compounds into carbon dioxide

Which enzyme is responsible for converting malate to pyruvate in the C4 cycle?

• PEP carboxykinase

• NADH dehydrogenase

• Rubisco

• ATP synthase

What is the role of the malate shuttle in C4 plants?

• Malate shuttle is involved in the breakdown of starch in C4 plants.

• Transporting malate from mesophyll cells to bundle-sheath cells for CO2 concentration and reduction of photorespiration.

• Malate shuttle is responsible for transporting sucrose in C4 plants.

• The malate shuttle in C4 plants helps in the synthesis of ATP.

How is phosphoenolpyruvate (PEP) regenerated in the C4 cycle?

• Through the enzyme phosphoenolpyruvate carboxylase (PEPC)

• Through the enzyme pyruvate phosphate dikinase (PPDK)

• Through the enzyme pyruvate kinase

• Through the enzyme malate dehydrogenase

Which enzyme is responsible for converting oxaloacetate to phosphoenolpyruvate (PEP) in C4 plants?

• PEP carboxylase

• ATP synthase

• Pyruvate kinase

• Rubisco

What is the significance of the C4 cycle in hot and arid environments?

• Enhance water loss and increase photorespiration

• Minimize water loss and reduce photorespiration

• Promote water loss and reduce photosynthesis

• Decrease water loss and promote photorespiration

What is the main advantage of the C4 cycle over the C3 cycle in terms of photosynthetic efficiency?

• Less efficient in utilizing sunlight and producing ATP

• No difference in photosynthetic efficiency compared to C3 cycle

• Higher photosynthetic efficiency and reduced photorespiration

• Lower photosynthetic efficiency and increased photorespiration

How does the C4 cycle minimize photorespiration compared to the C3 cycle?

• Enhanced light absorption in the C4 cycle

• Spatial separation of initial carbon fixation from the Calvin cycle

• Temporal separation of initial carbon fixation from the Calvin cycle

• Increased efficiency of Rubisco enzyme