Now, the red blood cell, or haemoglobin, transports oxygen to where it is urgently
needed to produce energy - in our muscle cells. No fewer than 430 skeletal muscles
have to be kept supplied, all those musclesthat keep us standing up straight and help us to
move our limbs, wrinkle our brows, laugh - you name it. Nearly half of our body weight is
made up of muscles, and they can't function unless they receive fuel and oxygen.As in the
auto-mobile engine, the fuel is burned with aid of oxygen,releasing the energy needed for our
muscles to work.
In an engine, this combustion occurs in the cylinders. A mixture of gasoline and
air is made to explode with a spark from the spark plug. If it weren't for oxygen,
the explosion would never take place. That is why oxygen constantly has to be drawn in
through the carburettor. In our muscles, the combustion occurs in the cell - or, more specifically,
in the mitochondria.Mitochondria are tiny power plants located deep in the interior of a muscle
cell. A muscle cell doesn't just have one of these power plants, it has hundreds of them. A heart
muscle even has ten thousand. And that's where the oxygen has to go - to these power plants.
From the gatekeeper to the power house: transportation inside the cell
The red blood cell can only take oxygen to the gatekeeper of the muscle cell.
From there it is transported to the power plants by myoglobin. Myoglobin is the
stuff that makes your muscles red. If the power plants are only working at half-capacity,
the transfer of oxygen is slow and full of bureaucratic red tape. Once the muscle starts
warming up, however,all the red tape is cast aside and the transfer goes by in a flash.
Otherwise the power plants wouldn't be able to work at full throttle - during jogging, for
example. So, if the blood temperature goes up, the red blood cell hands over theoxygen
quickly to the myoglobin, which rushes it lickety-split to the chugging power plants.
As long as enough oxygen is supplied, combustion takes place withsufficient oxygen, or
"aerobically." (There's that word again, whichmeans so much to us runners.) And we
know what is burned along with the oxygen: glucose and fatty acids.
We also know what waste products are produced by combustion: water and
carbon dioxide. Unlike oxygen, carbon dioxide is easily soluble in water. It
therefore doesn't need its own means of transportation to get fromthe cell to the lungs.
It diffuses directly from the cell to the capillary blood,where it joins the water in the
blood plasma for further transportation to the alveoli in the lungs. Once the carbon dioxide
arrives there, it is exhaledthrough the lungs. The water produced by combustion remains
for themoment in the body, unless the body has to be protected from overheating,in which
case we "sweat it out".