What component of Earth's atmosphere exists entirely as a result of photosynthesis?

oxygen gas
water vapor
nitrogen gas
carbon dioxide gas

Match the digestive enzymes to the macromolecules they to digest. break down fats into glycerol and fatty acids break down carbohydrates into simple sugars break down nucleic acids into nitrogenous bases and simple sugars break down proteins into amino acids

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?

The third stage of cellular respiration is (2 points)