Questions: According to the passage, Antarctic fish are limited during the Antarctic winter by which of the following? The energy store available to replace expended energy The amount of wastes that can be expelled by their kidneys The amount of ions and molecules in their blood and tissue fluids Their ability to depress the freezing point of their bodily fluids

Transcript text: The Antarctic marine environment is inhabited by fish that produce remarkable antifreeze compounds. Such compounds depress the freezing point of the body fluids of fish. For most marine fish, salts (particularly sodium chloride) account for 85 percent of the depression of the freezing point below zero degrees Celsius. The rest of the depression can be attributed to small amounts of potassium, calcium, urea, glucose, and amino acids, all common constituents of blood and tissue fluids. In the Antarctic fish, however, these ions and molecules account for only 50 percent of the depression of the freezing point. The balance of the depression comes from eight different glycopeptides, each consisting of repeating units composed of a two-sugar molecule covalently bonded to a peptide chain of three amino acids. Antarctic fish have limited energy stores, and must therefore conserve energy, particularly in the Antarctic winter, when the productivity of the ecosystem is particularly low. How do they maintain an adequate supply of antifreezes without expendina areat amounts of enerav on svnthesis? According to the passage, Antarctic fish are limited during the Antarctic ${ }^{50}$ winter by which of the following? The energy store available to replace expended energy The amount of wastes that can be expelled by their kidneys The amount of ions and molecules in their blood and tissue fluids Their ability to depress the freezing point of their bodily fluids