LM 17: The Carbon Cycle

What are the ways in which the C₄  pathway differs from the C₃ pathway?

-The C₄ pathway has two fixation steps

-The C₄ pathway uses PEP carboxylase to initially fix CO₂

 -The C₄ pathway occurs in mesophyll cells and bundle-sheath cells

The illustration above shows a cross-section of a C₄ plant leaf. Bundle-sheath cells are packed tightly around vascular tissue. Based on your knowledge of the C₄ pathway, what are the structures labelled A in this diagram?

mesophyll cells

The illustration above shows a cross-section of a C₄ plant leaf. Bundle-sheath cells are packed tightly around vascular tissue. Which structures transport water from the roots to the photosynthetic cells?

vascular tissues

The illustration above shows a cross-section of a C₄ plant leaf. Bundle-sheath cells are packed tightly around vascular tissue. Transpiration of water occurs via which structures in this diagram?

stomata

Which true statement is accurate about CAM carbon fixation?

The CAM cycle fixes carbon and performs light reactions at different times of the day

What is the benefit of fixing carbon in bundle-sheath cells in the C₄ pathway?

CO₂ can be collected in high concentrations during the day. 

Why do both C₄ and CAM plants use PEP carboxylase instead of rubisco in their initial CO₂ fixation step?

PEP carboxylase has a higher affinity for CO₂ than rubisco and does not bind to O₂

The specialized C₄ and CAM pathways enable plants to still produce carbohydrates while conserving water. What would happen if a plant lost too much water through open stomata?

Light reactions will slow due to absence of electrons from water.

Autotrophs are organisms that create their own organic food molecules without ingesting other organisms (auto="self", trophos="feeder"). Based on this definition, what role do autotrophs play in the carbon cycle? 

producers

Heterotrophs are organisms that obtain their organic food molecules from ingesting other organisms (hetero = "other", "trophos"="feeder). Based on this definition, what role do heterotrophs play in the carbon cycle?

consumers