how-is-obtained-the-energy-that-makes-our-body-work
Energy is obtained from nutrients in food, such as glucose, protein and carbohydrates. To begin with, energy is not just any molecule: it is our body’s capacity to perform work, that is, to exert force or cause displacement. But for a little piece of our daily bread to become energy, it is not enough that it be swallowed, chewed and digested. It has to be broken down into small molecules that can be taken up by cells.
Glucose is the main one of these molecules. Human beings, during the evolutionary process, were able to better use the glucose that comes from food, extracting the maximum amount of energy from it. Bacteria, for example, obtain only 4% of their potential, while the human body transforms 30% of the energy it consumes into work, the same as a car.
The rest of the glucose goes towards maintaining the body’s vital activities, such as heartbeats and brain synapses. Therefore, we have to fuel our “machine” several times a day. It’s just not worth going around robbing the fridge. To function well, a person must consume, on average, 30 calories per kilogram of their weight. A person weighing 64 kilos, for example, should have a daily diet of around 2,000 calories.
GLUCOSE IN THE VEIN
Molecule works as fuel and is broken down to become energy for the body
1- As a piece of bread is millions of times larger than a cell, the first step is to break it into smaller and smaller portions, the carbohydrates, through chewing and digestion. This happens until the carbohydrate is reduced to its smallest unit: glucose. In the small intestine, it is absorbed by the venous system, proceeds to the liver, peripheral tissues and finally to the cell.
2- Glucose enters the cytoplasm, the watery portion of the cell, and undergoes its first division. One molecule of glucose gives rise to two molecules of pyruvic acid. In bacteria, respiration ends here – so their energy use is much lower.
3- The pyruvic acids go to the mitochondria, the organelle responsible for cellular respiration. To obtain more energy, the Krebs cycle, a sequence of reactions, begins. In this phase, the acid loses hydrogens, which go to other molecules, and carbons. These bind to the oxygen available in the cell, generating CO2, which comes out in respiration. At the end of the cycle, all of the glucose carbons turn into CO2.
4- The hydrogens that came out of the 5 molecule of pyruvic acid tend to bind to the oxygen in the breath. When uniting in the mitochondrial crest, hydrogen and oxygen form the famous H2O molecule. Part of this water is eliminated, and another part remains inside the cell acting on chemical reactions and helping to form the cytoplasm.
5- But there are some H+ ions left, which are attracted to the inner side of the membrane, which is loaded with negative ions. To do this, they go through a specific path, a kind of umbrella-shaped “turbine”, the ATP-synthase, which rotates and binds a phosphate, which is already in the cell, to an ADP, which is also there. , forming ATP, which is free to participate in other reactions in our cells.
6- One of the reactions that uses energy is muscle contraction. Two of the muscle proteins do the contractions: actin and myosin. Myosin binds ATP coming from mitochondria, and bends over actin. The ATP then breaks down, releasing a phosphate and an ADP, which are free to be recharged again. Thus, actin and myosin slide over each other, performing the movement. For the two to release and the muscle to relax, another ATP needs to bind to myosin, turning the two proteins off.
ENERGY ACCOUNT
Where does the energy produced by the body go*
BRAIN0 – 19%
Synapses (communication between neurons) consume most of the energy. As it has little glycogen in reserve, the brain can suffer severe damage when glucose is lacking, even for a short period of time.
SKELETAL MUSCLES – 18%
Muscle contractions require a lot of energy. In intense physical activity, the muscles use glycogen, which they store in large quantities.
HEART – 7%
The heart relies heavily on immediate energy from glucose. Therefore, mitochondria are more abundant in cardiac muscle than in skeletal muscle.
SPLEEN AND LIVER – 27%
It is mainly in the liver that our energy stock – glycogen – is stored. It’s from him that we draw energy while we sleep, for example.
KIDNEYS – 10%
Most of this energy is used to produce urine. The rest is used to make hormones or eliminate toxins.
REST OF THE BODY – 19%
CHARGED BATTERY
ATP, or adenosine triphosphate, is like a battery: it charges and discharges each time the H+ moves the “turbine”. But what does ATP have to do with the bagel? Every time 1g of glucose is burned, 4 calories are released, recharging thousands of ATPs. To attend an hour of class, for example, your body consumes about 126 calories, that is, at least 30g of carbohydrates are needed, which corresponds to a bread.
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CONSULTANCY: MARITSA BORTOLI, NUTRITIONIST AT THE FACULTY OF PHARMACEUTICAL SCIENCES AT USP; CLÁUDIO FURUKAWA, PHYSICIST AT USP; MARISA FERNANDES AND VILMAR BALDISSERA, FROM THE DEPARTMENT OF PHYSIOLOGICAL SCIENCES AT THE FEDERAL UNIVERSITY OF SÃO CARLOS *DATA FROM THE DEPARTMENT OF MEDICAL PHYSICS AT THE UNIVERSITY OF NOTRE DAME, IN INDIANA, USA