The pressure flow mechanism in phloem is initiated and maintained by _________.
A. The high water potential of soil water driving water flow throughout the plant
B. Active transport of ions such as H+ and K+ into the phloem at many sites along the phloem tissue
C. Loading substances, such as sucrose, into sieve-tube elements at sources and unloading them at sinks
D. Water flowing from source to sink by osmosis
E. Loading of sucrose into the phloem sink by osmosis
Ans: C. Loading substances, such as sucrose, into sieve-tube elements at sources and unloading them at sinks
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Fifteen high school students visited a local farm in central Wisconsin for a weekend where they enjoyed petting farm animals, riding horses, and campfire meals
With sanitation in mind, only one individual remembered to wash her hands with water pumped from a well after petting the animals before dinner. After two weeks of the girl passing out at random occasions, she was rushed into the emergency room where doctors determined she was severely dehydrated. Explain how it took direct observation of a fecal sample to solve this potential life-threatening disease and how this disease was treated in the otherwise healthy girl. Also mention any necessary precautions the individual should have taken after being diagnosed with the disease. What will be an ideal response?
DNA renaturation (hybridization) can be used to (select all that apply):
A. determine whether a DNA strand from one species is complementary to a DNA strand from another species. B. cleave long fragments of DNA into smaller fragments for analysis. C. amplify small samples of DNA by replicating them. D. identify the sequence of a DNA strand. E. none of these.
The ________ was developed in the late 1920s by Theodore Svedberg. He originally used it to determine the sedimentation rate of proteins.
Fill in the blank(s) with the appropriate word(s).
Hyperpolarization of the postsynaptic nerve terminal
A) decreases the chance that an action potential will be initiated. B) increases the chance that an action potential will be initiated. C) does not affect the initiation of an action potential. D) is stimulated by an influx of calcium ions. E) none of the above