Why do new red blood cells survive for only a few months?
A) The oxygen that red blood cells carry damages their organelles.
B) Red blood cells do not have most organelles or a nucleus.
C) The heart pumps red blood cells so often that their membranes deteriorate.
D) The hemoglobin that red blood cells carry is toxic.
Answer: B
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Enzyme regulation may occur by several methods. Which of the following is not a means of enzyme regulation?
A) substrate-level phosphorylation B) feedback inhibition C) allosteric regulation D) covalent modification E) saturation
What on a female has the same embryonic tissue as a male and is very sensitive?
What will be an ideal response?
How does the early development of the mouse differ from that of Caenorhabditis?
a. Embryonic mouse cells commit to their ultimate fate earlier than do the cells of Caenorhabditis. b. Early development of a mouse is regulative, while early development of Caenorhabditis is not. c. Mouse cells require higher concentrations of nutrients than do the cells of Caenorhabditis. d. Embryonic mouse cells differentiate much later than the cells of Caenorhabditis. e. Embryonic development in the mouse is controlled by transcription factors, while Caenorhabditis is not.
One hypothesis that has been proposed regarding the origin of life suggests that life evolved from an "RNA world" to today's "DNA world
" Considering the properties of RNA and DNA molecules, which questions would direct an investigation of the most insightful test(s) of this hypothesis? A) Is it likely that RNA molecules functioned as ribozymes to synthesize DNA from amino acids, and that this role was reversed when DNA became the information source? B) Is it likely that simple, yet stable RNA molecules served as a primitive precursor to a less stable DNA molecule that was more capable of storing more information? C) Could RNA have provided a template for DNA assembly, thereby enabling a more stable molecule that is replicated more accurately? D) Since ribozymes could freely enter and leave the vesicles, could these molecules have brought external DNA into the cell as a less stable, but more reliable storage molecule of double-stranded DNA?