Understanding the Calvin Cycle and C-4 Photosynthesis

The video explains the Calvin Cycle and the role of the RuBisCo enzyme in photosynthesis. It highlights the problem of photorespiration, where oxygen interferes with carbon fixation, reducing efficiency. The anatomy of leaves, including stomata, is discussed to understand how plants manage gas exchange. The video introduces C-4 photosynthesis, a mechanism in some plants that minimizes photorespiration by using PEP carboxylase to fix carbon dioxide in mesophyll cells, transferring it to bundle-sheath cells for the Calvin Cycle, thus creating an oxygen-free environment for efficient photosynthesis.

What is the primary role of the RuBisCo enzyme in the Calvin Cycle?

• To transport water within the plant

• To facilitate the Calvin Cycle by fixing carbon dioxide

• To fix oxygen into organic molecules

• To convert light energy into chemical energy

What is the main issue caused by photorespiration in the Calvin Cycle?

• It enhances the efficiency of photosynthesis

• It leads to the production of phosphoglycolates instead of phosphoglycerates

• It reduces the need for carbon dioxide

• It increases the production of ATP

What is the function of stomata in plant leaves?

• To absorb sunlight for photosynthesis

• To facilitate the exchange of gases, including carbon dioxide and oxygen

• To store water for the plant

• To transport nutrients from the soil

How do C-4 plants initially fix carbon dioxide?

• By using PEP carboxylase to form a 4-carbon molecule

• By storing it in vacuoles

• By using RuBisCo to form a 3-carbon molecule

• By directly converting it into glucose

What is the role of PEP carboxylase in C-4 photosynthesis?

• To fix oxygen into organic molecules

• To fix carbon dioxide into a 4-carbon molecule

• To transport water within the plant

• To convert light energy into chemical energy

In C-4 photosynthesis, where does the Calvin Cycle occur?

• In the stomata

• In the chloroplasts of guard cells

• In the mesophyll cells

• In the bundle-sheath cells

Why is C-4 photosynthesis more efficient in hot, dry environments?

• It allows plants to close their stomata and conserve water

• It produces more ATP

• It requires less sunlight

• It increases the rate of oxygen fixation

What is the significance of the bundle-sheath cells in C-4 plants?

• They provide a low-oxygen environment for the Calvin Cycle

• They absorb sunlight for photosynthesis

• They transport nutrients from the soil

• They store excess water

How does the C-4 pathway help in reducing photorespiration?

• By using more ATP

• By separating the initial CO2 fixation and the Calvin Cycle into different cells

• By increasing the concentration of oxygen

• By closing the stomata during the day

What is the first stable product formed in C-4 photosynthesis?

• 3-phosphoglycerate

• Oxaloacetate

• Glucose

• Ribulose bisphosphate