Significance of the Laws of Thermodynamics in Metabolic Reactions

Energy conversions whether it is in a physical, chemical or biological system are all dependent on the Laws of Thermodynamics. These laws can, in a biological sense, be deployed in metabolic reactions or in the photosynthetic processes where sunlight facilitates the conversion of sugar into utilizable energy for the plant.

The conversion processes in a biological system can be from one form to the other. For instance, the chemical energy stored in animals which is derived from photosynthesis can be converted to electrical energy as in the case of the electric fish and the conversion of chemical energy to mechanical energy as is seen in the contraction of muscle tissues of some animals or in the conversion of chemical energy(from food) to light energy as seen in luminescent organisms such as the glow-worm.

The First Law of Thermodynamics

This law states that when one form of energy is converted into another form there is no net loss or gain. This implies that in the conversion process the total energy at the end of the process is equal to the amount of energy at the beginning of the process. It must be noted that not all the energy used in a conversion process are deployed entirely into the new form. Some of the energy can be lost as it is used in overcoming frictional forces or some can be dissipated as heat.

The Second Law of Thermodynamics

This law states that when one form of energy is converted in to another form, some of the energy is lost as heat. In biological systems, when sugar is broken down not all the energy liberated is used in reconversion processes or in synthesizing more complex molecules because some of these energy is lost as heat which is very useful especially in warm-blooded animals which contributes significantly in the maintenance of a constant body temperature.                     

Activation Energy In Biological Systems

The energy required to overcome an energy barrier in a conversion process is known as the Activation Energy. It is the energy that is required to overcome the inertia(reluctance of a system at rest to get underway) and go to completion. The sugar molecule needs a small amount of energy(activation energy) before the process of oxidative breakdown can get underway.

The concept of Activation Energy in thermodynamics brings us to the significance of the Speed of Biological Reactions. When two molecules combine chemically to form a large molecule or macromolecule, there are factors that affect the speed at which the reaction goes to completion. This means that any factor that increases the rate of molecular collision would definitely increase the speed of a biological reaction because the reacting species or molecules are in a state of continual random motion. These factors generally affect speed of biological reactions:-

(i) The concentration of the substrate

(ii) The temperature of the reactants and the system

(iii)The presence of a catalyst.

(iv) Increasing the pressure and

(v) Removal of water molecules in which the substrates are dissolved in.

Any factor that increases collision of the reacting molecules would increase the speed of a reaction. Catalysts are very significant in speeding up reactions and a biological system is not left out. The substrate molecules are adsorbed onto the surface of the catalyst and as a result of the close proximity they have been brought into, they react much more quickly. The product produced then leaves the surface of the catalyst, remaining unchanged by the process and is therefore available for reuse. In biological systems, a different kind of catalysis powered by enzymes is observed unlike what we see in an inorganic system where inorganic catalysts such as iron, sulphuric acid, platinum and zinc play a major role.

The 4 Laws of Thermodynamics

Let’s take a more in depth look at the 4 laws if thermodynamics as it affects to metabolic reactions.

The primary tasks of a living cell are to obtain, transform, and use energy. These processes may seem simple but the underlying reality is more complicated.

Consider a simple example: an ant colony in a highly ordered state before an earthquake destroys it. The entropy of the ants’ system increases after the earthquake.

First Law of Thermodynamics

The first law of thermodynamics states that energy is conserved, even when it is transferred or converted from one form to another. This energy may be in the form of heat, kinetic energy or potential energy. It cannot be created or destroyed. The energy that is released during a chemical reaction, for example, can be transformed to kinetic energy in your legs as they move while you walk or into heat that warms your hands.

The law can be restated as where DU is the change in internal energy of the system, Q is the net heat transfer into the system and W is the work done on or by the system. The first law expresses the relationship between these three quantities in terms of a single variable, internal energy. The change in internal energy does not depend on the path taken to reach it, and therefore DU = Q + W is a thermodynamic constant.

In the case of a chemical reaction, the direction in which the change in internal energy occurs is determined by the Gibbs free energy of the system. A reaction will occur spontaneously in the direction that results in a negative Gibbs free energy. This is because a reaction with positive Gibbs free energy requires an input of energy to overcome its energy barriers, whereas a reaction with a negative Gibbs free energy has the opposite effect and releases energy into its surroundings.

Another way of thinking about the first law is to consider what would happen if all of the energy transfers involved in a process went backwards. For example, if the heat from a hot object moved into a cold cup of water, the water would cool down and the coffee would warm up. This is because the entropy of the system would decrease as the heat left the hot cup and increased in the cold cup, which is the opposite of what should happen during a spontaneous process.

Living systems, such as the cells in your body, are highly complex and require a lot of energy to function properly. As living systems convert this energy into useful forms, such as kinetic energy and potential energy, they must lose some of it in the form of waste products or byproducts that are not usable. This loss of energy increases the entropy of the surrounding environment. This is why the laws of thermodynamics are necessary to explain the processes that take place in living systems, such as metabolism and photosynthesis.

Second Law of Thermodynamics

One of the most important principles to know about energy transfers is the second law of thermodynamics. This principle states that as energy moves from one form to another, it always loses some of its potential energy as heat. It also states that a system cannot have its overall entropy decrease, as this would require an input of energy from outside the system.

This law is significant in metabolic reactions because energy stored in molecules like glucose is converted to other forms of energy during the cellular respiration process. This energy is then used to perform work, such as moving a cell’s organelles or heating the body.

The energy transferred in this process is measured by the free energy change of the reaction, which is equal to the difference between the enthalpy of the reactants and the enthalpy of the products. For a spontaneous process, this free energy change must be negative, meaning that the overall entropy of the system and its surroundings increases. The temperature, pressure and volume of the system are also increased by this process, according to Boston University.

This increase in entropy is known as the entropy of the universe, which is the sum of the randomness and disorder of the particles in the universe. As the universe continues to expand, its entropy will always increase. Living organisms, on the other hand, are made of highly organized structures and have low entropy.

When a system reaches its equilibrium, it has achieved the lowest possible entropy. This is why processes that appear reversible, such as ice melting in a glass of hot water, are not truly reversible. It is impossible to reverse a process that has reached its equilibrium.

The second law of thermodynamics is a fundamental principle that occurs all around us. It is not just limited to chemical reactions, but also applies to physical, mechanical and electrical systems. While this principle is a universal phenomenon, it is important to note that the second law of thermodynamics can only be applied to a system at equilibrium. For non-equilibrium systems, such as a mixture of gases or a biological system, the laws of thermodynamics are more complex and are described by statistical mechanics.

Third Law of Thermodynamics

The third law is a key concept that relates energy transfers to the total entropy of a system. It states that a system’s entropy tends toward a minimum value as it approaches absolute zero temperature (zero kelvin or absolute zero). This concept is important because if a thermodynamic system can achieve a state of perfect equilibrium, its entropy will be zero. Theoretically, all pure substances that exist in a crystalline form at absolute zero temperature will have a fixed entropy value of zero. This is a general principle and it applies to any system that can be cooled down to absolute zero temperature, including liquids, gases, solids and mixtures of these substances.

Any adiabatic reversible process that takes place at or close to a system’s lowest possible temperature (i.e., the state of maximum entropy) must have a net decrease in entropy. The entropy change associated with this type of reversible process is proportional to the ratio of the system’s temperature before and after the process. This is a fundamental property of the reversible processes that can take place at or near zero temperature and it is known as the Nernst-Simon heat theorem.

Biological organisms are closed systems, and the transfer of energy between a living cell and its surroundings is essential to the operation of these cells. These energy transfers take the form of chemical bonds breaking and forming, and thermal movement of molecules in the surrounding environment. In addition, the cells themselves release energy into their surroundings by doing work in their metabolisms. In all of these energy transfers, some portion of the original chemical bond energy is lost as unusable heat energy.

The second and the third laws of thermodynamics seem to contradict each other in that the cells are generating order (as opposed to destroying order) but the cells cannot do this alone. The energy needed to generate order is provided by its surroundings in the form of food and photons from the sun or, in the case of some chemosynthetic bacteria, from inorganic molecule-based energy sources. Then, in the course of its metabolic reactions, a living cell transfers some of this disordered energy into order forming molecules in its own body.

Fourth Law of Thermodynamics

The Fourth Law of Thermodynamics is an important principle that states that a system’s total entropy always increases as the number of possible states for its atoms or molecules decreases. It is the opposite of the First Law of Thermodynamics, which states that energy cannot be created or destroyed, but can only change form. Energy can be transformed by transferring heat, producing mechanical work, or by chemical reactions. Examples of each are a fan that converts electrical energy into mechanical energy by pushing air, or a plant that absorbs solar energy to transform it into chemical energy.

The Four Laws of Thermodynamics are a set of principles that govern the transfer and conversion of energy between systems. They are an important part of the physical rules that govern our universe. They are the foundation of chemistry, physics, biology, and many other disciplines.

In thermodynamics, energy is described in terms of a system’s temperature, kinetic energy, and potential energy. The Four Laws of Thermodynamics describe the relationships between these three variables and how they affect matter. They are also essential for understanding how biological processes, such as metabolic reactions, work.

The Four Laws of Thermodynamics also explain why living organisms are never in equilibrium. They are open systems that constantly exchange energy and matter with their surroundings. This energy is transferred both by spontaneous chemical reactions, known as catabolism, and non-spontaneous thermal activities, such as breathing. Living organisms must always perform work at a cost to balance their free energy against the required energy for their existence under existing conditions.

Despite the fact that the Four Laws of Thermodynamics provide an essential framework for understanding how energy is transferred and converted in biological systems, there are many other concepts and ideas that need to be taken into account. For example, a significant amount of energy is lost during the conversion of mechanical energy into thermal energy. This is why it is very important to understand the underlying mechanics of thermodynamics when designing a building. Unless this is done, the resulting building may not be as energy efficient as it could be.