Bioenergetics refers to the study of the energy flow within living organisms, specifically plants. This includes the processes of photosynthesis, respiration, and other metabolic pathways involved in the conversion of energy from one form to another within plant cells.
Photosynthesis is the process by which plants convert light energy into chemical energy, which is stored in the form of organic compounds such as sugars. Respiration is the process by which plants break down organic compounds to release energy for use in cellular processes. Other metabolic pathways involved in bioenergetics in plants include the production and breakdown of pigments, such as chlorophyll, and the synthesis of essential molecules such as ATP (adenosine triphosphate).
Understanding bioenergetics is important for botanists because it allows them to study the mechanisms by which plants capture and utilize energy from the environment. This knowledge can be used to develop new techniques for optimizing plant growth and productivity, as well as for understanding the impacts of environmental stressors such as climate change on plant energy metabolism.
ENERGY AND IT’S VARIOUS FORMS:-
In bioenergetics, energy is the capacity of a biological system to do work, such as moving muscles, pumping ions across membranes, and synthesizing macromolecules. Energy can exist in various forms, including:
CHEMICAL ENERGY: This is the energy stored in the chemical bonds of molecules, such as glucose, ATP, and NADH. When these bonds are broken, energy is released and can be used to do work.
ELECTRICAL ENERGY:This is the energy associated with the movement of charged particles, such as ions, across membranes. This movement generates a potential difference or voltage, which can be used to do work, such as powering muscle contractions or nerve impulses.
THERMAL ENERGY: This is the energy associated with the random motion of molecules and atoms. It can be transferred from one system to another as heat, and can be used to do work, such as maintaining body temperature or driving metabolic reactions.
RADIANT ENERGY: This is the energy associated with electromagnetic radiation, such as light. Photosynthetic organisms use this energy to convert carbon dioxide and water into glucose and oxygen.
MECHANICAL ENERGY: Mechanical energy is the energy of motion or movement. In bioenergetics, mechanical energy is involved in muscle contractions and movement of cells. For example, muscle cells use ATP to power the movement of myosin and actin filaments, causing muscle contractions.
Energy of a system may be defined as the capacity of a system to do work. This capacity may be bound in the molecules. The bound form of energy is called Potential energy.In the biological systems the main source of potential energy is the solar energy gets fixed up in the form of Chemical energy of carbohydrates molecules during photosynthesis in green plants.
The molecules in motion posses capacity to carry out work.The energy possessed by a molecule or a body due to its motion is termed as kinetic energy. This type of energy depends upon the mass of the body and it’s velocity.
★Formula of kinetic energy★
The formula for kinetic energy (KE) is:
KE = 1/2 * m * v^2
Where: m = mass of the object v = velocity of the object
This formula states that the kinetic energy of an object is directly proportional to its mass and the square of its velocity. It is important to note that kinetic energy is a scalar quantity, which means that it only has magnitude and not direction. Additionally, the SI unit of kinetic energy is joule (J), which is defined as the work required to accelerate a mass of one kilogram at a rate of one meter per second squared.
PRINCIPLES OF THERMODYNAMICS:-
The principles of thermodynamics play a fundamental role in bioenergetics, which is the study of energy flow and transformations within living organisms. The two main laws of thermodynamics are particularly relevant in this field:
★The First Law of Thermodynamics, also known as the Law of Conservation of Energy, states that energy cannot be created or destroyed, but can only be converted from one form to another. This law applies to all energy transformations that occur in living organisms, including the conversion of chemical energy stored in food molecules into usable energy in the form of ATP.
★The first law of thermodynamics is the principle of conservation of energy applied to thermodynamic systems, and it states that:
★The change in internal energy of a closed system is equal to the sum of the heat added to the system and the work done on the system.
★In mathematical terms, this can be expressed as:
ΔU = Q – W
★where ΔU is the change in internal energy of the system, Q is the heat added to the system, and W is the work done on the system.
★Here, ΔU, Q, and W are all quantities that are expressed in the same units of energy, such as joules (J) or calories (cal). The first law of thermodynamics is a fundamental principle in thermodynamics that plays a key role in the study of energy transformation and heat transfer in physical systems.
•In the first law of thermodynamics, the external work “w” done by the system on its surroundings is defined as the work done by the system on the external environment, which can include mechanical work, electrical work, and other forms of work.
ΔU = Q – w
where ΔU is the change in the internal energy of the system, Q is the heat supplied to the system, and w is the external work done by the system on its surroundings.
If the system performs work on the surroundings, then the sign of w will be negative, indicating that energy is leaving the system. On the other hand, if work is done on the system by the surroundings, then the sign of w will be positive, indicating that energy is entering the system.
★The Second Law of Thermodynamics states that in any energy conversion process, the total amount of usable energy in the system decreases, and the degree of disorder or randomness (entropy) increases. This law implies that energy conversions are never 100% efficient, and that some energy will always be lost as heat. This is particularly relevant in biological systems, where the efficiency of energy conversion is often low due to the need to maintain a high degree of order and organization within the cell.
KELVIN PLANCK STATEMENT:-
“It is possible to obtain a continuous supply of work from a body or engine that can transfer heat from a single heat reservoir”
•The Kelvin-Planck statement is one of the three fundamental statements of the second law of thermodynamics. It states that it is impossible to construct a heat engine that operates in a complete cycle and produces no effect other than the extraction of heat from a hot reservoir and the performance of an equivalent amount of work. In simpler terms, it means that no heat engine can operate with 100% efficiency and convert all the heat energy into useful work. Some heat energy must always be wasted or rejected to a cooler reservoir. This statement has significant implications in the design and efficiency of real-world heat engines, such as internal combustion engines, gas turbines, and refrigeration systems.
“it is impossible to transfer for a self acting machine,unaided by any external agency to convert heat continuously from one body at lower temperature to a body at lowest temperature to a body at a higher temperature
The difference between the first and second law of thermodynamics lies in the fact that the first law of concerned with the accounting of the various kinds of energy involved in a given process,while the second law is concerned with the availability of the energy of a given system for doing useful work.
The second law of thermodynamics introduce the concept of entropy which may be regarded as the amount of energy unavailable for conversion into work.
GIBB’S FREE ENERGY:-
Free energy refers to the energy available to do useful work in a system. In thermodynamics, free energy is a measure of the amount of energy that can be extracted from a system at constant temperature and pressure.
The concept of Gibbs free energy is named after the American scientist Josiah Willard Gibbs. It is defined as the energy of a system that is available to do work at constant temperature and pressure. It is denoted by the symbol G and is expressed in units of joules.
Gibbs free energy takes into account the enthalpy (H) and entropy (S) of a system. The enthalpy represents the total energy of a system, including its internal energy and the work done by or on the system. The entropy, on the other hand, represents the disorder or randomness of a system.
The equation for Gibbs free energy is given as:
G = H – TS
where T is the absolute temperature and S is the entropy.
If G is negative, it means that the reaction is spontaneous and can proceed without any external input of energy. If G is positive, it means that the reaction is not spontaneous and requires an input of energy to proceed.
In summary, Gibbs free energy is a measure of the amount of energy available to do useful work in a system. It takes into account the enthalpy and entropy of a system and can be used to predict the spontaneity and direction of a reaction.
Relation between ∆G and ∆S:-
In thermodynamics, the relationship between the change in Gibbs free energy (∆G) and the change in entropy (∆S) is given by the following equation:
∆G = ∆H – T∆S
where ∆H is the change in enthalpy (heat content) of the system, T is the temperature in Kelvin, and ∆S is the change in entropy (the measure of disorder or randomness) of the system.
The equation shows that the change in Gibbs free energy (∆G) depends on both the change in enthalpy (∆H) and the change in entropy (∆S). A negative ∆G indicates that a reaction is spontaneous, while a positive ∆G indicates that a reaction is non-spontaneous.
If ∆H is negative (exothermic reaction) and ∆S is positive (increased disorder), then ∆G will be negative and the reaction will be spontaneous at all temperatures. If ∆H is positive (endothermic reaction) and ∆S is negative (decreased disorder), then ∆G will be positive and the reaction will be non-spontaneous at all temperatures.
Energy Rich Compound:-
The primary energy-rich compound in bioenergetics is adenosine triphosphate (ATP). ATP is a nucleotide that consists of a nitrogenous base (adenine), a five-carbon sugar (ribose), and three phosphate groups. The high-energy bonds between the phosphate groups store energy that can be used by cells to carry out various metabolic processes, including muscle contraction, active transport, and synthesis of macromolecules.
When ATP is hydrolyzed by the enzyme ATPase, it releases energy and forms adenosine diphosphate (ADP) and inorganic phosphate (Pi). This process, called ATP hydrolysis, is exergonic, meaning it releases energy that can be used by the cell. The energy released by ATP hydrolysis is used by the cell to drive endergonic reactions, such as protein synthesis, DNA replication, and other cellular processes.
On the basis of free energy of Hydrolysis of ATP and other Organophosphates. The same divided into two groups:
(1)Low Energy Compound:
A low energy compound is a molecule that contains less energy in its chemical bonds compared to high energy compounds. Low energy compounds are typically involved in energy-consuming reactions, whereas high energy compounds are involved in energy-releasing reactions.
One example of a low energy compound is adenosine diphosphate (ADP), which is formed when ATP (adenosine triphosphate) releases energy by breaking one of its phosphate bonds. ADP can then be converted back into ATP through the addition of a phosphate group, which requires energy from an outside source such as food or sunlight.
Another example of a low energy compound is NAD+ (nicotinamide adenine dinucleotide), which is used as an electron carrier in cellular respiration. NAD+ accepts electrons from other molecules and becomes reduced to NADH, which can then be used to generate ATP through the electron transport chain. NADH, in contrast, is a high energy compound because it contains more potential energy in its chemical bonds than NAD+.
(2)High Energy Compound:
In Bioenergetics, high energy compounds are molecules that store a large amount of potential energy that can be used to drive cellular processes. These compounds typically contain phosphate groups and are involved in energy transfer reactions such as ATP hydrolysis.
The most well-known high energy compound in bioenergetics is adenosine triphosphate (ATP). ATP is a nucleotide that consists of a nitrogenous base (adenine), a sugar molecule (ribose), and three phosphate groups. The high energy of ATP is stored in the bonds between the phosphate groups, which can be broken by hydrolysis to release energy.
Another example of a high energy compound is phosphocreatine, which is found in muscle cells. Phosphocreatine is similar in structure to ATP, but it contains a creatine molecule instead of an adenine molecule. Like ATP, phosphocreatine can donate a phosphate group to ADP to form ATP, providing a source of energy for muscle contractions.
Other high energy compounds in bioenergetics include guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytidine triphosphate (CTP), which are similar in structure to ATP and play important roles in cellular metabolism.