Sports activity is one of the most energy-consuming processes. The (seemingly) simple act of running is propitiated by the movement of an endless number of levers, activated by the perfect synchronization between muscles and bones by means of nervous impulses.
To generate nerve impulses and mobilize this entire musculoskeletal mechanism, the human body uses the energy (ATP) it gets from the nutrients we ingest. But do you know how you get ATP, the energy that moves the Runner, from food?
In this article I will explain how your body is able to transform food through complex chemical processes into ATP molecules, thus generating the energy needed to perform all the activities you do. Find out!
Mitochondria: the cell’s power plants
The symbiotic association between the cell and the mitochondria occurred millions of years ago was a great step for the evolution of life, from this moment the cell acquired its own autonomy, ie had its own power station and rechargeable.
One milliliter of mitochondria develops a power of 1 watt, consumes 4.32 liters of oxygen, produces 20 kilocalories of heat, synthesizes around 1.25 kg of ATP degrading 5 grams of glucose.
Its purpose is to obtain energy through a series of oxidation-reduction reactions (electronic transfer).
The human being at rest consumes approximately 40 kg of ATP per day and a person who does sport consumes ½ kg more per minute of practice.
Carbohydrates (or carbohydrates)
Coming from the vegetable world, carbohydrates are degraded into monosaccharides as final products, they are taken to the liver and muscles where they are transformed into glycogen.
Fats (or lipids)
The body uses fats for energy, but in this case it is a more long-term oriented energy reserve.
Contributed by the diet, they must be degraded in the stomach by enzymes being reduced to amino acids. They constitute the basic structural element of all the cells of our tissues. Energy generation (ATP) is therefore not the main purpose of proteins, except in exceptional circumstances, but of fats and carbohydrates.
The organism has evolved in such a way that it can use both aerobic (with oxygen) and anaerobic (without oxygen) processes to obtain energy. In both cases, the start of the process starts with the glucose molecule, which must be broken down for energy (ATP).
1 glucose molecule under anaerobic conditions produces 65 calories.
1 molecule of glucose under aerobic conditions produces 656 calories.
Our body consumes 160 grams of glucose a day. The amount of glucose we can store is about 190 to 200 grams between liver glycogen and skeletal muscle glycogen and 15 to 20 grams in other body fluids. This means that we have reserves for one day, so we have to keep on synthesising it.
Each molecule of ATP produces 30.6 kilojoules and this energy is released when one of the phosphorus (-P) bonds is broken. The ATP is not used to store energy, but as an immediate donor, being its duration of only one minute.
The main systems for obtaining energy are:
- The Phosphorus system or Alactic Anaerobic.
- The Glycogen System: Anaerobic Glycolysis or Lactic Fermentation.
- The Oxidative System: Aerobic Glycolysis-Krebs Cycle-Transport
of electrons-Oxidative Phosphorylation.
The phosphorus system obtains energy by direct rupture of the phosphorus bonds.
The organism has the capacity when it has a fast, abrupt and great demand of energy to obtain it by two ways:
- From the Adenosine Triphosphate molecule (ATP).
- From the phosphocreatine molecule.
From molecules of ATP (Adenosine triphosphate) by means of its hydrolysis, we obtain about 7,000 calories per mol.
ATP + H2O ——————————– ADP + P (+Energy)
The amount of ATP that can be stored in the muscles is very small, only gives us to maintain muscle power for about 3 seconds, so we can run about 25 meters.
From Phosphocreatine molecules (PC) by breaking the phosphorus bond is generated ATP energy, in excess of the previous process, in the order of 10,300 calories per mole.
The body has 2 to 4 times more Phosphocreatine than ATP. The use of this route gives us enough energy to travel about 75 meters, that is, we can maintain muscle power from 7 to 8 seconds.
By both ways simultaneously our body is able to obtain energy in an explosive and intense way for a period of 8 to 12 seconds, that is to say to travel about 100 meters.
The glycogen stored in the liver and muscle tissue is broken down into glucose in an O2-deficient medium.
Anaerobic Glycolysis or Lactic Fermentation: in the absence of oxygen
Muscle tissue often uses the path of lactic fermentation or glycolysis. ATP molecules are formed at 2.5 times the rate provided by the mitochondria’s oxidative mechanism. It is used in intense and short term efforts.
The combined action of the two systems allows the muscles to generate movement during the first minutes of high intensity.
To go deeper into this subject I recommend you read my entry on the importance of lactic acid in the body.
Oxidative System: in the presence of oxygen
Glucose transformed into two pyruvate molecules when in the presence of oxygen passes into the mitochondria and follows a different path from the previous one, called the Krebs Cycle, Citric Acid or Tricarboxylic Acids.
The final balance per glucose molecule of this cycle is 2ATP+4CO2+6 NADN+2FADH2, the latter two compounds being coenzymes transporters of high energy electrons and responsible for moving the electrons to the next step, the Electron Transport System.
Electron Transport System and Oxidative Phosphorylation
It develops in the inner membrane of the mitochondria. It is really an electronic transfer process that conserves much of the free energy of electrons in the form of phosphate bond energy (ATP). To better understand Oxidative Phosphorylation, I recommend you watch the following video.
The efficiency of all the processes described together: Glycolysis (by aerobic route), Krebs Cycle, Respiratory Chain and Oxidative Phosphorylation, is the obtaining of 36 ATP from a simple glucose molecule, which allows muscle tissue cells to get enough energy to do high-intensity, long-lasting work.
6 CO2 + H2O + 36 ATP
As a summary, I have made the following table relating the degree of intensity of the physical activity that we develop and the system of obtaining energy that our organism will use to satisfy the energy demand.
If physical activity is prolonged, the power decreases to the point that there is a perfect coupling of the Cardiorespiratory System and the Vegetative Nervous System, so that muscle contractions will become more spaced, reaching a stable state where the degradation processes are equal to the synthesis processes and the oxygen demand becomes very small. So much so that in long-distance races it is very easy to pass from one power to another, depending on the obstacles encountered along the course. In this way, great efforts can be made over long periods of time.
I hope this article has been interesting to you, and allows you to know better how our body gets the energy you use to run, think and ultimately, to be alive. In this way you will understand that the human body is a wonderful gift, a perfect machine. Take care of it!
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In a next post I’ll tell you about the next step: How the body transforms energy (ATP) into muscle movement. Don’t miss it!