When sodium ions move from one cardiac muscle cell to an adjacent cell, causing them to contract in unison, this is an example of
A. endocrine signaling.
B. paracrine signaling.
C. contact-dependent signaling.
D. direct intercellular signaling.
E. autocrine signaling.
Answer: D
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tRNA differs from other types of RNA because it _____
a. acts as an enzyme b. is only involved in transcription c. binds to mRNA d. codes for multiple amino acids e. is complexed with a protein
Charles Darwin
a. lived in New England.. b. studied to become a doctor. c. followed his avocation as a sailor. d. is identified with the concept of natural selection. e. sailed on the H.M.S. Bassett.
The tRNA shown in the figure above has its end projecting beyond its end. What will occur at this end?
A) The amino acid binds covalently. B) The excess nucleotides (ACCA) will be cleaved off at the ribosome. C) The small and large subunits of the ribosome will attach to it. D) The cap of the mRNA will become covalently bound.
Female birds lay their eggs, thereby facilitating flight by reducing weight. Which "strategy" seems most likely for female bats to use to achieve the same goal?
A) limit litters to a single embryo B) refrain from flying throughout pregnancy (about six weeks long) C) give birth to underdeveloped young, and subsequently carry them in a pouch that has teats D) feed multiple embryos internally using placentas