If this question makes sense (I don’t know if it does) the answer could enable comparison to determination of such efficiency on theoretical grounds. A 2000 article by He et al, ATP consumption and efficiency of human single muscle fibers with different myosin isoform composition, suggests maximum single muscle fiber efficiency in the range of 21% to 27%, but presumably there are mechanical or friction and heat losses resulting in a lower level of efficiency. As well, muscle cells are only one kind of cell in the body. Is there research that can address this question?
In order to calculate efficiency for a cell (or tissue), the cell must be capable of performing external work (i.e., efficiency = external work/energy input). Work = force x distance. Only cells with motor proteins (e.g., myosin/actin) can act on the environment and perform external work. This eliminates the possibility of calculating efficiency for most cell types other than skeletal, cardiac, or smooth muscle cells.
What a great q and a. This is exactly why I enjoy this forum.
I might suggest that, if an index of efficiency of mammalian cells other than those mentioned by Dr. Warren is of interest, perhaps the following example might be a useful starting point.
Let's say that the efficiency of a cell is arbitrarily defined very narrowly by a researcher to fit the needs of a project. For my example, let's say I'm interested in anti-inflammatory efficiency. For my needs, I may choose to define that as the amount of IL-10 secreted by a given cell or given number of cells, of a specific cell type, in a given time, relative to the ATP cost. Oversimplifying it a bit, I'm defining efficiency as the "bang for your buck" that you get from ATP expenditure.
Dr. Warren, Dr. Markert,
Thank you both for your helpful and thoughtful replies.
I think there are some theoretical ways (from a biophysics perspective) to possibly approach estimating the efficiency of the global BMR of an animal, or at least a lower bound for such efficiency, but was perplexed at the absence of global determination of BMR efficiency which would be helpful for testing theory against measurement. There seem to be articles estimating measured muscle tissue metabolic efficiency but I could not find articles for the animal body overall. Dr. Warren's reply explains why looking for data for global cellular BMR efficiency is likely to be in vain. So Dr. Warren's is very helpful information.
The ATP idea seems like a good idea. Does the nature of cellular ATP and its cellular metabolic efficiency depend on the kind of cell?
I agree with Dr. Markert, that the RG question format can be (sometimes interesting and) very helpful. Thank you both of you.
Best wishes.
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