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
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One important aspect of self-incompatibility is to prevent:
A. expression of deleterious homozygous recessive genes B. genes that may prevent pollen germination C. factors that keep pollen from developing D. matings between different species of plants E. adherence of pollen to the stigma surface
Individuals considered at greatest risk for contracting brucellosis are:
a. dairy farmers. b. fishermen. c. prison guards. d. those working with exotic birds.
Memory is ____
a. the storage and retrieval of sensory or motor experience b. the response to stimuli based on experiences c. the awareness of ourselves and surroundings d. voluntary e. involuntary
Identify negative feedback component B
a. integrator b. sensor c. stimulus d. response e. effector