In order for our muscles to work, they need energy. We can’t just plug into an outlet. That’s why every cell in our body has “accumulators” in which energy is stored. They are called ATP. They are so called because of their name in chemical language – Adenosine Triphosphate. It is very easy to get some energy from each of these molecules and therefore they are ideal for energy transfer.
How energy is derived from ATP
An ATP molecule consists of two parts, adenosine and three phosphoric acid residue molecules.
It is these three residues that are responsible for the accumulation of energy. More specifically, energy is stored in the bonds between them. If only one phosphoric acid residue is attached to adenosine, then the battery is depleted. If another residue is attached to this molecule, then the battery is half charged. And if a third residue is added, then the battery is fully charged.
In order to attach the residue, you have to expend energy. And inversely, if that residue is detached from ATP, then that energy is released. It’s like compressing a spring. If you let go of the spring, it is able to push some object with its energy.
But there is one problem. Compared to other molecules, the ATP molecule is quite large. And you can’t store a lot of such “accumulators”. For example, in order to store enough energy to run 10 km, the body needs about 30 kg of such molecules, i.e. one third, or even half of the whole body must consist of ATP, which, of course, is impossible.
How energy is stored in the body
The body does not store a lot of ATP, but constantly recharges those molecules that are discharged. For this purpose, we have a special fuel – glycogen. It consists of huge “beads”. Each “bead” is a glucose molecule. There is such a reserve in the cytoplasm of every cell in the body. When the cell needs energy, a special enzyme breaks off one glucose molecule from the “beads” and throws it into the furnace – it performs several chemical reactions, during which energy is released, which ATP absorbs. That’s it, the battery is charged and can be used.
And one molecule of glucose can charge more than one molecule of ATP. How much depends on whether oxygen is involved in the process. With oxygen, you can charge up to 38 ATP from a single glucose molecule (aerobic respiration, from the Greek aero for “air”). Without oxygen, only 2 ATP (anaerobic breathing – from the Greek an – “no” and aero – “air”). This is actually why we breathe – to extract maximum energy due to the presence of oxygen.
How the body works when there is a lack of oxygen
During intensive exercise, energy consumption increases. In the beginning, when there is enough oxygen and ATP is charged as efficiently as possible, everything is fine. But gradually there is not enough oxygen to charge ATP through the aerobic pathway. But energy is still needed and anaerobic – oxygen-free – respiration comes into play. It’s less efficient, but there’s no choice. At this point we feel considerable fatigue.
Но наш организм адаптируется под новые условия. Сосуды расширяются, чтобы увеличить приток крови, и, соответственно, кислорода, который в ней содержится. Некоторые органы вроде пищеварительной системы начинают меньше кровоснабжаться, чтобы задействовать больше крови на нужды мышц. Лёгкие начинают работать интенсивнее, чтобы кровь насыщалась кислородом в большей степени. Сердце работает быстрее, чтобы справляться с возросшей нагрузкой.
And thanks to all this, the body adapts, and the muscles start to get enough oxygen. And they can switch back to aerobic energy consumption.
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