Chapter 7: Mitochondria

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VARIATIONS IN
INTERNAL STRUCTURE
The mitochondria of brown adipose tissue are exceedingly numerous and have an
extensive internal membrane surface. The accompanying micrograph shows part of an
adipose cell from the interscapular region of a bat collected near the end of its period of
hibernation. The cell is depleted of lipid and most of the cytoplasm is occupied by large
spherical mitochondria. The unusual number of mitochondria in this tissue and their
abundant cristae are believed to be related to the high energy requirements for the
synthesis of fat from carbohydrate. In the mitochondria of this organ, oxidation is
incompletely coupled to phosphorylation. Therefore during arousal from hibernation,
much of the energy from oxidation of fat is dissipated in the form of heat which helps
raise the body temperature to normal.
Figure 237. Interscapular brown adipose cell from the bat, Eptesicus fuscus.
Figure 237
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