Final answer:
Thermogenin, found in the inner mitochondrial membrane of brown fat, facilitates nonshivering thermogenesis, crucial in newborn mammals for heat generation rather than ATP. It responds to cold exposure and is vital for maintaining body temperature in infants who lack sufficient insulative body fat.
Step-by-step explanation:
In brown fat, thermogenin present in the inner mitochondrial membrane uncouples ATP synthesis from electron transport in infants and other newborn mammals. Thermogenin, also known as uncoupling protein 1 (UCP1), facilitates the process of nonshivering thermogenesis, where the usual production of ATP is bypassed, and energy is instead released as heat.
This is particularly important for newborn babies as they are more susceptible to heat loss due to their larger surface area to mass ratio. Brown adipose tissue, which contains these specialized mitochondria with thermogenin, plays an essential role in maintaining body temperature in newborns by metabolizing stored fat into heat rather than ATP.