What is a "Nucleus"? the structure that forms the surface of a cell separating its contents from the
outside world
an organelle of some eukaryotic cells in which photosynthesis occurs, using the
energy of light to make organic compounds from carbon dioxide and water
a cell organelle that is essential to cell functions including reproduction, contains
the cell's chromosomes, and is enclosed by a membrane
membrane-bound organelles in eukaryotic cells in which cellular respiration
takes place, using oxygen to break down glucose to carbon dioxide and water
and putting the energy into a more readily usable form in ATP molecule

Epinephrine is a hormone released from the adrenal gland of the body, most often in a stressful situation. it is known as the "fight-or-flight" hormone. one way that it causes a response in the body is to activate receptors on muscle cells. where are these cellular receptors located? a. on the cell membrane b. in the nucleus c. on the cell wall d. around the mitochondria

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

Keeping in mind the life cycle of bacteriophages, consider the following problem: during the reproductive cycle of a temperate bacteriophage, the viral dna inserts into the bacterial chromosome where the resultant prophage behaves much like a trojan horse. it can remain quiescent, or it can become lytic and initiate a burst of progeny viruses. several operons maintain the prophage state by interacting with a repressor that keeps the lytic cycle in check. insults (ultraviolet light, for example) to the bacterial cell lead to a partial breakdown of the repressor, which in turn causes the production of enzymes involved in the lytic cycle. as stated in this simple form, would you consider this system of regulation to be operating under positive or negative control?