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In the body, lipolysis of triacylglcerols (TAGs) releases free fatty acids (FFAs). However, many of these FFAs are not catabolized, but are instead re-esterified back into TAGs, even during starvation. The movement of fatty acids to and from esterification can be termed the flux of FFAs.

When a compound is simultaneously being synthesized and catabolized, this is known as
Select Option conservation of energya futile cyclea metabolic interrupta recycling phase
. The percentage of FFAs that are not used for fuel but rather re-esterified is
Select Option <10%~25%~50%~75%
. This re-esterification occurs in both the
Select Option adipose tissuebrainkidneylung
and the
Select Option muscleliverpancreasspleen
. Additionally, the absolute number of FFAs in flux changes; however, the percentage of recycled FFAs
Select Option also changes proportionally to the concentration of FFAs in fluxalso changes, but not proportionately to the concentration of FFAs in fluxremains constant, no matter the concentration of FFAs in fluxcan vary as any of the above
. Although the reason for this breakdown and subsequent reformation is not well-understood, speculation is that this process occurs, even in starvation, because
Select Option the inefficiency of the cycle helps prevent mutation in lipolytic enzymesthis process avoids oxidation and therefore functions as an antioxidantthis process conserves ATP that would be needed to 'charge' the acyl groupsthis process reserves energy that may be needed for a "fight or flight" situation
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