Substance A is secreted by the liver, travels through the circulatory system bound to a carrier protein and causes a
change in gene expression in its target cell. Substance A is therefore a ligand for ____.
a. a receptor tyrosine kinase
b. a G-protein-coupled receptor
c. a steroid hormone receptor
d. a ligand-gated ion channel
e. guanylyl cyclase
ANSWER: c
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The interconnectedness of plants, animals, and microbes with each other and their environment.
A) ecosystem B) genetic engineering C) vaccine D) FDA E) population
Two 6-base sequences are present in bacterial promoters: TATAAT (located 10 nt upstream from the start site) and TTGACA (located 35 nt upstream from the start site). What is the significance of the fact that these two base sequences are different?
A. Binding sites for both the holoenzyme and ATP are provided. B. It allows RNA polymerase to distinguish between the template strand and the coding strand of the DNA molecule. C. The transcription bubble can be properly formed. D. Binding sites for both the core polymerase and holoenzyme are provided. E. Both the location of the start site and the direction of transcription can be established.
________ are membrane proteins that help cells to stick to each other
Fill in the blank(s) with correct word
Which of the following is not a type of temperate grassland?
A) veld B) pampas C) prairie D) chaparral