A neuron synthesizes and secretes substance D, which binds to a receptor on the neuron cell membrane, triggering an
influx of calcium. Substance D therefore is a ligand for a ____.
a. a receptor tyrosine kinase
b. a G-protein-coupled receptor
c. a hormone receptor
d. a ligand-gated ion channel
e. guanylyl cyclase
ANSWER: d
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Bacteria in the ?-proteobacterial clade ________ are the most abundant organisms on Earth and demonstrate unique adaptations to life in the oligotrophic open ocean.
What will be an ideal response?
_____ stimulation causes the pupil to widen
a. Sympathetic b. Parasympathetic
he nervous system of many species of flatworms:A
consists of a single, large ganglion in the anterior end. B. is sometimes referred to as tubelike. C. includes two dorsal nerve cords. D. is diffuse and netlike. E. is a “ladder-type.”
The four haploid nuclei found at the end of meiosis differ from one another in their exact genetic composition. Some of this difference is the result of
a. cytokinesis. b. replication of DNA during the S phase. c. separation of sister chromatids at anaphase II. d. spindle formation. e. crossing over during prophase I.