Water diffuses through certain organs such as the kidneys and bladder much faster than would occur by passive diffusion through a lipid bilayer alone. What accounts for this more rapid rate of water transport in these organs?
A. The composition of lipids changes to promote water transport.
B. Presence of aquaporin channels for facilitated diffusion of water.
C. Presence of a water pump.
D. Presence of an ATP-driven enzyme for water transport.
E. The presence of molecules that bind water and change its membrane permeability properties.
B. Presence of aquaporin channels for facilitated diffusion of water.
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Which of the following does not contribute to the infectious ability of prions?
A. Prion proteins are not digested. B. Prion proteins can induce the misfolding of normal proteins. C. Prion proteins can enter the bloodstream. D. Prion proteins are deposited as aggregates. E. Prion diseases progress slowly.
In radiation therapy, cancer cells are killed by ____
a. carbon b. radium c. iodine d. thallium e. nitrogen
How is the coma of a comet produced?
a. Rocky material breaks off from the comet to form the coma. b. The coma is a cloud of particles that the comet has swept up in its orbital path. c. Ices vaporize to become gas that forms the coma around the comet. d. Particles in the solar wind get caught in the comet's magnetic field to form the coma.
The binding of a plant hormone to its receptor
typically induces
a. an increase in membrane permeability. b. an enzyme-substrate cascade. c. an inhibition of protein synthesis. d. a change in gene expression. e. increased DNA replication activity