Chemical energy. It is the one that occurs in chemical reactions. A cell or a battery has this type of energy
Summary
[ hide ]
- 1 Chemical reactions
- 1 Stored chemical energy
- 2 Chemical energy in food
- 3 Combustion
- 4 Chemical energy in the body
- 5 Biochemistry of cellular respiration
- 6 See also
- 7 Sources
Chemical reactions
Humanity has used chemical reactions to produce energy since its existence . From the most rudimentary, of wood or coal combustion , to the most sophisticated, which take place in the engines of modern airplanes or spaceships.
The chemical reactions, then, are accompanied by a release, or in other cases by an absorption, of energy.
How much energy can a chemical reaction produce? Where does that energy come from? How can it be measured and calculated?
Stored chemical energy
Energy is an inherent property of matter. Matter has stored energy that is due, on the one hand, to the position or height of a [[body] (kinetic energy]]) and, on the other, to the nature or substances of which the body is made. Reference is made, since each element or compound corresponds to a certain amount of stored chemical energy, which is called energy content.
When a chemical phenomenon takes place, it is accompanied by a manifestation of energy, whether there is absorption or release of it, due to the chemical energy stored by the substances
This means that when the stored chemical energy of the reactants is greater than the energy of the products, there is a surplus of energy that is released, since the energy remains constant, that is, it is neither created nor destroyed.
For example, when methane (fuel gas) reacts with oxygen (oxidizing gas), there is an evolution of energy as a product, because the energy content of methane and oxygen is greater than that of carbon dioxide and water, which are the substances that form during the reaction:
Therefore, if, by reacting, one or more substances produce others with higher energy content, there will be energy absorption by the reagents, as shown by the following photosynthesis reaction:
Substances with a high energy content are used as fuel, since when reacting with oxygen a large amount of energy is generated in the form of light and heat .
Chemical energy in food
Food also stores chemical energy and through these organisms obtain the energy necessary to live, that is, to form and renew tissues, maintain their temperature, perform muscular work, etc.
Food contains nutrients such as carbohydrates , lipids (fats), proteins and vitamins , which are called biogenetic (because they are of organic origin); other nutrients of inorganic origin are water and minerals such as sodium, phosphorus, sulfur, chlorine, cobalt, manganese and zinc.
Organisms use food to obtain energy and nutrients from them; the latter are decomposed to be used in cell growth and restoration. This transformation process is called metabolism.
The energy that can be metabolized from carbohydrates is 4 kcal per gram; of lipids, 9 kcal per gram and of proteins, 4 kcal per gram. It is recommended that in an adequate diet, foods that provide approximately 3,000 kcal per day (depending on the physical activity performed), that contain, in a balanced way, all the nutrients, be eaten.
For example: 75 g of protein, 80 g of lipids and 400 to 500 g of carbohydrates. In addition, it should be considered that water is very important as a nutrient and that humans need 2 to 2.5 liters per day, although food also provides a proportional amount of it that is known as metabolic water.
It is necessary to remember that organisms obtain energy through an autotrophic or heterotrophic mechanism.
The autotrophic mechanism is typical of plants, algae and cyanobacteria that, from carbon dioxide and light energy from the Sun , produce oxygen and glucose . More complex molecules are formed from the latter.
The heterotrophic mechanism is characteristic of organisms like those of animals; These ingest the previously prepared food (carbohydrates, lipids, etc.), their cells oxidize it through respiration and thereby produce CO2 , water vapor and other waste substances.
- Efficiency of an internal combustion engine
The chemical reactions of burning carbon compounds with oxygen to release energy are well known to all. They occur, for example, when burning wood or gas in the oven or when the gasoline of a car provides the necessary energy for its operation. These reactions are too violent and too little controlled for living organisms to use within a cell.
For an engine to work, it requires fuel that, when reacting, gives off energy. In the case of the internal combustion engine, the energy of the fuel is transformed into power and movement, in such a way that the force produced serves to operate a bus, a propeller and a generator, among other things.
The engine four stroke is the internal combustion engine better known, and its operation is carried out in four stages, which they are:
First time (intake): the penetration of a mixture of fuel and air into the intake valve takes place when the piston is lowered .
Second time (compression): the piston rises and compresses the mixture by reducing the volume.
Third time (explosion): when igniting the spark plug, it causes the mixture to explode; at this time the piston is pushed down.
Fourth time (expulsion): the gases produced by the explosion are expelled through the expulsion valve; at this time the piston lowers.
Schematic representation of the operation of a four-stroke engine.
The combustion
Combustion is violent oxidation, which, in turn, releases energy in the form of heat and light. The main products of it are: CO2, water vapor and energy.
Examples of this process are the combustion of stove gas, firewood, and coal. In all these phenomena oxidation occurs and, therefore, a reduction also takes place, since when combustion of one of these substances occurs, oxygen is reduced, gaining electrons and the element that is oxidized loses them.
In the organism of living beings there are processes of “organic combustion”, which are named for the similarity they have with the products obtained. However, they are not properly combustions, as they are not violent oxidations.
An example of these is the degradation of glucose that, during cellular respiration, produces CO2 , water and energy, according to the following reaction:
In this equation it is observed that each oxygen atom “gains” 2 electrons (it is reduced) and the carbon “loses” 4 electrons (it is oxidized).
The oxidation of butane gas is an inorganic combustion, since it does not take place in living beings. His reaction is as follows:
Chemical energy in the body
The cells require energy to perform most biological processes. Energy comes from the food we eat.
The oxygen present in the air we breathe combines with the carbon and hydrogen atoms present in food molecules, releasing energy and forming carbon dioxide and water after numerous steps.
The original food source is green plants. They are able to use solar energy, carbon dioxide from the air and water to create complex organic molecules made up of carbon, hydrogen and oxygen and rich in energy.
These molecules are of three basic types: carbohydrates, lipids, and proteins. Any of these groups can combine with oxygen and generate the energy necessary for life.
Animals cannot generate carbohydrates, lipids, or proteins from simple molecules of carbon dioxide, water, and using solar energy. Instead, they feed on plants that have already done this work or other animals that have already devoured plants.
Biochemistry of cellular respiration
The conversion of nutrients into energy occurs during the so-called catabolism processes. The fundamental currency of energy within cells is a molecule called ATP. The structure of this molecule is such that it contains chemical bonds capable of releasing a lot of energy when breaking.
Biochemistry
- Two fundamental examples of catabolism are:
- Fermentation .
- Breathing .
Fermentation is an energy generation process that does not depend on the presence of oxygen. The end products of the process are small organic molecules like ethanol. This is the process by which alcoholic beverages are generated.
Breathing is a process that does require oxygen and that generates greater amounts of energy through complete oxidation, releasing carbon dioxide and water. The energy comes ultimately from the food we eat. These are subjected to various enzymatic processes that convert them into smaller molecules that form the basis of energy generating mechanisms.
