Aldosterone is a hormone secreted by the adrenal cortex, and insulin is a peptide secreted by the pancreas
When aldosterone contacts a target cell, it binds to an intracellular receptor
and migrates to the nucleus; insulin binds to extracellular receptors on the plasma
membrane. What is the most likely reason for this difference?
A. Aldosterone is hydrophilic and therefore
must enter the aqueous environment of the
cytoplasm to have an effect.
B. Aldosterone is lipid-soluble and therefore
easily crosses the phospholipid bilayer of the
plasma membrane.
C. Aldosterone is too small to bind
extracellular receptors on the plasma
membrane.
D. Insulin is too large to interact with DNA.
B
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Which of the following lack chlorophyll and are totally dependent on the host plant for water and nutrients?
A. hemiparasites B. holoparasites C. all plant parasites D. root parasites E. hemiparasites and root parasites
________ is a directional movement in response to a graded chemical stimulus.
Fill in the blank(s) with the appropriate word(s).
Protonephridia are found in
a. annelids. b. mammals. c. flatworms. d. insects. e. adult mollusks.
Two species interbreed occasionally and produce vigorous, fertile hybrids. When the hybrids breed with each other or with either parent species, however, the offspring are feeble or sterile. These species are affected by
A) gametic isolation. B) reduced hybrid fertility. C) reduced hybrid viability. D) hybrid breakdown.