How cells breathe

Inhaling oxygen is only the first step in a long journey through the nooks and crannies of the body.

The oxygen is then transported via the blood to all cells in the body. The same goes for nourishment from food we eat. Inside the cell, the oxygen and nourishment are transformed into energy and carbon dioxide, which we breathe out. In a new dissertation from Stockholm University in Sweden, Kristina Faxén has mapped how so-called cell breathing takes place.

I am studying how cells breathe. In recent years, more and more diseases, like Alzheimer’s, have shown to have to do with cell respiration. The findings are expected ultimately to lead to drugs specifically designed for various disorders, although that’s far down the road,” says Kristina Faxén, a doctoral candidate at the Department of Biochemistry and Biophysics at Stockholm University in Sweden.

Every cell contains many tiny energy power plants-­the mitochondria. The enzymes that govern cell breathing are located in membranes that surround the mitochondria. Kristina Faxén has analyzed one of these enzymes-­cytochromoxidase. This is a pump that distributes positive and negative charges to opposite sides of the membrane, thereby functioning roughly like a battery charger that helps to “charge our inner batteries.” These batteries power all bodily functions, such as our muscles, brain, and digestion.

“To study this ‘battery charger’ my colleagues and I have managed to construct artificial cells consisting of a globe-shaped membrane, something like a soap bubble, but only 30 nanometers (millionths of a millimeter) in diameter. Then we introduced cytochromoxidase to the membrane. In this way, it can function just as in a living cell,” she says.

One thing that makes the reaction difficult to study is how quickly it happens. A single ‘breath’ in the cell takes only a thousandth of a second. The laboratory at Stockholm University is one of the few in the world that possesses the advanced laser technology needed to study such rapid processes.

“Several research teams around the world have studied molecular pumps, trying to understand how they work. But there has been no unanimity about any general mechanism. Our findings have solved some of the conflicts. Previously we presented an extremely simple and general principle for the functioning of the pumps that shows how a swinging arm fetches positive charges, protons, on one side of the membrane and leaves them on the other side. The findings of my dissertation support this model,” says Kristina Faxén.

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