What is the C4 pathway? Briefly explain how this adaptation increases the effectiveness of photosynthesis in these plants. What will be an ideal response?
In the C4 pathway, CO2 reacts with PEP in a reaction catalyzed by PEP carboxylase, and
oxaloacetate is formed as the product. This reaction occurs in mesophyll cells. In turn,
oxaloacetate is converted to malate, the malate diffuses into bundle sheath cells, and is
decarboxylated to pyruvate. The CO2 thus formed enters the Calvin cycle. The C4 pathway
enables photosynthesis to occur more efficiently in hot, dry environments when plants
normally close their stomata to prevent water loss. In such cases, the C3 pathway is inhibited
because the O2 that accumulates in photorespiration outcompletes low levels of CO2 for the
active site of RuBP carboxylase/oxygenase. However, because PEP carboxylase binds only
CO2 and not O2, plants having the C4 pathway can thrive when the CO2 levels are low.
You might also like to view...
How do nastic movements differ from tropisms?
A. Nastic movements are slower than tropisms. B. Nastic movements only occur in the dark. C. Tropisms are directional responses to directional stimuli; nastic movements are the same regardless of the direction of the stimulus. D. Nastic movements happen after a stimulus, tropisms happen during a stimulus. E. Nastic movements are not reversible.
The structure indicated by the letter "B" above represents _____
a. actin b. a myofibril c. myosin d. the sarcoplasmic reticulum e. a muscle fiber
The ________ zone is a range of environmental temperatures within which homeothermic metabolic rates are minimal
Fill in the blank(s) with correct word
RNA usually is ________ stranded
Fill in the blank(s) with correct word