The exoskeleton of insects is composed mainly of what material?
A. chitin
B. calcium carbonate
C. hydroxyapatite
D. collagen
E. waxes
A
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Which of the following best describes the tRNA binding sites of the ribosome?
A. Only one of the three sites can be occupied by a tRNA molecule at any given time. B. Each tRNA that associates with the ribosome must first bind in the P site and then move to the A site. C. The P site contains the tRNA molecule covalently bound to the growing chain of amino acids. D. All tRNAs leave the ribosome through the A site.
An electron microscope must use electromagnet "lenses" shaped like donuts to direct the electrons onto the specimen. Why?
A. Electrons are particles-there are also particles in air. Without a vacuum, the electrons would strike and be scattered by the atoms/particles within the air. B. Because electrons are highly radioactive, and the chamber must be completely sealed to prevent them from escaping and contaminating the lab area. C. This is the method for fixing the specimen to the slide grid for an electron microscope. Without fixing the specimen by vacuum, it would slide off and we wouldn't be able to visualize it. D. All of the above are true.
How is C4 photosynthesis able to achieve higher concentrations of CO2 in the vicinity of rubisco than photosynthesis in C3 plants can?
A. by separating carbon capture from carbon fixation B. by suppressing photorespiration C. by capturing HCO3-instead of CO2 D. because the C4 cycle is faster than the Calvin cycle
Imagine that you could microinject cytochrome c into the cytosol of both wild-type cells and cells that were lacking both Bax and Bak, which are apoptosis-promoting members of the Bcl2 family of proteins
Would you expect one, both, or neither of the cell lines to undergo apoptosis? Explain your reasoning.