QUESTION OF THE WEEK -
What role do "uncouplers" serve in brown fat mitochondria in bears during winter sleep?
Hey Boo Boo, lets go see what's in that picinic basket!
Acetyl-CoA (a product of the catabolism of either glucose or fat found in picnic baskets) is broken down in mitochondria to carbon dioxide (CO2). Some of the energy released in this process is "saved" when ADP is phosphorylated to form ATP on the mitochondrial inner membrane. This inner membrane must be intact (not leaky) to function properly. When bears are sleeping in the winter (not true hibernation since their body temperature does not drop significantly), a small membrane protein (thermogenin) is synthesized in brown fat mitochondria that allows protons to equilibrate across the inner membrane. These inner membranes thus "leak" protons. Interestingly, human infants (large surface to volume ratio, little hair...) use the same mechanism for the same purpose!
Questions: What effect would the presence of this protein have on the process of ATP synthesis in brown-fat mitochondria? Why are these proteins called "uncouplers"? What effect does this uncoupler have on the organism?
8/22/04 Copyright (C) 2004,
Jonathan Monroe, firstname.lastname@example.org.
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