Final answer:
White adipocytes hold lipids in a single large droplet, while brown adipocytes store lipids in multiple small droplets and contain many mitochondria that enable thermogenesis, generating heat rather than ATP.
Step-by-step explanation:
A defining feature of white and brown adipocytes, respectively, is: A) Large lipid droplets; many mitochondria B) Large lipid droplets; few mitochondria C) Large nucleus; many small lipid droplets.
White adipocytes are characterized by the storage of lipids as a single large droplet, and they are metabolically less active compared to brown adipocytes. They are excellent at storing large amounts of fat, which is apparent in obese individuals. Brown adipocytes, on the other hand, store lipids as many small droplets and contain a high number of mitochondria. These mitochondria are responsible for the brown adipose tissue's ability to burn fats to generate heat rather than ATP, rendering brown fat thermogenic. This heat generation is especially crucial for maintaining body temperature in cold environments or in newborns.