C4 Plants and Photorespiration Concepts

The video discusses the imperfections in photosynthesis, focusing on the enzyme rubisco, which can mistakenly bind oxygen instead of carbon dioxide, leading to photorespiration. This process reduces photosynthesis efficiency. C4 plants, like maize and sugarcane, have evolved to minimize photorespiration through Krantz anatomy, which separates rubisco from high oxygen concentrations. These plants fix carbon dioxide into a four-carbon molecule, oxaloacetate, in mesophyll cells, while the Calvin cycle occurs in protected bundle sheath cells. The video concludes with extension questions for further exploration.

What is the primary role of the enzyme Rubisco in photosynthesis?

• To bind oxygen to RuBP

• To close the stomata of the plant

• To fix carbon dioxide to RuBP

• To release oxygen as a waste product

What happens when oxygen binds to RuBP instead of carbon dioxide?

• Stomata open wider

• Photosynthesis rate increases

• More glucose is produced

• Photorespiration occurs

How does photorespiration affect the production of molecules in photosynthesis?

• It produces two 3-carbon molecules

• It produces one 4-carbon molecule

• It produces one 2-carbon and one 3-carbon molecule

• It produces two 2-carbon molecules

Which type of plants have evolved to avoid photorespiration?

• C4 plants

• Aquatic plants

• CAM plants

• C3 plants

What is the unique leaf anatomy called that helps C4 plants avoid photorespiration?

• Krantz anatomy

• Mesophyll anatomy

• Bundle sheath anatomy

• Stomatal anatomy

How do C4 plants manage to keep Rubisco away from high oxygen concentrations?

• By increasing the rate of photosynthesis

• By producing more oxygen

• By having a tight ring of mesophyll cells

• By closing their stomata

What molecule do mesophyll cells in C4 plants fix carbon dioxide into?

• Pyruvate

• RuBP

• Oxaloacetate

• Glucose

Where does the Calvin cycle occur in C4 plants?

• In the chloroplasts

• In the stomata

• In the bundle sheath cells

• In the mesophyll cells

Why can't air reach the bundle sheath cells in C4 plants?

• Because they are located in the roots

• Because they are covered by a waxy layer

• Because they are protected by a ring of mesophyll cells

• Because they are deep inside the leaf

How do C4 plants obtain the carbon dioxide needed for the Calvin cycle?

• From the soil

• From the atmosphere directly

• From the C4 molecules fixed by mesophyll cells

• From the oxygen produced during photosynthesis