Final answer:
Freeze-tolerant animals prevent intracellular ice crystal formation through antifreeze solutes, proteins, or glycoproteins that lower the freezing point and promote supercooling.
Step-by-step explanation:
In some freeze-tolerant animals, intracellular ice crystal formation is prevented by the presence of specific antifreeze solutes, proteins, or glycoproteins. These compounds inhibit ice crystal growth within the cells, thus protecting them from damage that would otherwise occur upon freezing. The ability to prevent ice formation is crucial for survival in cold environments as the formation of ice can rupture cell membranes and cause irreversible damage to the cell's structure.
These antifreeze compounds work primarily through two mechanisms: freezing point depression, which involves lowering the temperature at which the liquid in the cells becomes ice, and supercooling, where the liquid remains unfrozen even below its typical freezing point. For instance, adding glycerol to the water in cells temporarily replaces the water and contributes to lowering the freezing point. Some organisms also change the lipid composition of their cell membranes, increasing the proportion of unsaturated fatty acids, which maintains membrane fluidity at low temperatures.