Things We Don't Know About Biochemistry

It should be no surprise that vast swathes of uncharted territory remain to be explored regarding the biochemical workings of our bodies - yet many newly discovered items still have the capacity to surprise; the discovery of yet more uncharted territory in locations previously unsuspected of such. Take this, for example:

"Although cells are basic building blocks, their metabolic rates depend on where they find themselves living," said Van M. Savage, Ph.D., the lead author of the research and an instructor in the department of systems biology at Harvard Medical School. "Conceptually this is important because huge amounts of research on human diseases are done on single cells or cultured cells that come from other animals and little is done to place these findings within the context of the size or other whole-body properties of the animals."

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The question of whether cells are bigger in larger mammals than in smaller ones -- think of an elephant's liver cell compared with a liver cell from a mouse -- is usually answered by saying that larger mammals don't typically have bigger cells, they just have more of them.

Liver cells, red blood cells and other cell types that frequently divide and replace themselves are about the same size, but more permanent, long-lived cells, such as brain and fat cells, are indeed larger in large mammals.

"Fat cells increase in size tremendously if you move from a mouse to an elephant," said James Gillooly, Ph.D., an assistant professor in the zoology department of UF's College of Liberal Arts and Sciences. "Neurons also increase in size. But red blood cells are the same size whether they are in a mouse or an elephant. The reason brain and fat cells grow bigger could be because they live longer and have important long-term functions. In these cases, the properties of the cell are linked to the whole organism. But the sizes of quickly dividing cells are independent of the organism."

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"Despite the progress that has been made in cell biology, we still have a relatively poor understanding about general characteristics of cells across species," Savage said. "The focus has been on how cells affect the whole organism, not on how the size of the organism and its energy requirements affect the cells."

Size is a fundamental property of a cell; one would think that differences then lead to important differences in function. How then, do we account for this in our many experiments in animal models, as science grows in sophistication and level of attention to detail? Biochemistry is always more complex that we'd like to think it is - if it was simple, we'd be done already with the defeat of disease, aging and all other unpleasant realities resulting from absent knowledge and technology. It is humbling to see gaps in our knowledge still looming large in very basic areas of comparative biology.

This should be all the more reason not to regard rapid progress in medicine as a done deal, and this a world in which we just have to sit back and wait for the results. A great deal of hard work lies ahead in order to understand and control our bodies sufficiently well to avoid the fate of aging, suffering, disease and death that has met all of our ancestors to date. If you want to see that happen in time to help you, then you have to get up out of your seat and contribute.

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