Energy Changes; Do you really know about free energy

in this article we are going to discuss about the energy changes so well before we discussing about energy changes you have to know that what is is the changes of energy what are the example of energy? what is energy transfer? what is energy transformations? and what is Free energy? what is Entropy? what are the laws of thermodynamics? what is open and close system what is steady system ? and what is Homeostasis?


Both living and nonliving matter contain energy. Energy is the capacity to do work. It exists in several forms-mechanical, sound, radiant, thermal, chemical, potential and kinetic energy. The total energy ofa system is called enthalpy. The part of total energy that can perform work is free energy. The science that deals with energy kinetics of living beings is called bioenergetics.

Thermodynamics is a branch of physical science that deals with relations of heat and other forms of energy. The first law of thermodynamics says that energy can neither be created nor destroyed. Whenever work is done energy is either transformed or transferred. Both the types of energy changes occur continuously in the living matter or cell.
(a) Energy Transfer. It is the flow of usable energy from one source to another substance in the same form. For example, the food molecule glucose breaks down during cellular respiration and chemical energy present in its chemical bonds are released. The same is transferred to ATP during its synthesis from ADP and iP The chemical bond established between ADP and iP holds this energy and hence the bond is called high energy bond. Now chemical energy present in ATP becomes available for physiological activities leading to maintenance,repair, growth and development of the organism.

(b) Energy Transformation. It is conversion of one form of energy into another form.Many examples can be cited. Conversion of radiant or light energy into chemical energy during photosynthesis is an example of energy transformation. The potential energy stored in food molecule is transformed into chemical energy of ATP Chemical energy in ATP is transformed into light energy in glow worm. ATP energy is transformed to electrical energy in nerves for conduction of impulses.

Free energy

The living organisms perform numerous physical and chemical activities continuously Hence energy is used up continuously. In terms of thermodynamics, this usable energy is called free energy. It is that part of total energy of a system that can do work


When energy is used up for doing work, the system loses energy. Hence, the free energy of the system reduces. On the other hand, some energy is lost during the process of energy transfer or transformation. When such a loss of energy occurs repeatedly, there is an increase in disorderlyness or randomness which is called as entropy. The second law of thermodynamics states that “any system when left to itself tends to increase entropy.” Energy has a tendency to be uniformly distributed. It flows from high energy area to low energy area. During flow of energy, the particles in that area move at random and collide. This collision results in disorders. The motion of the particles consume energy which is finally lost in the form of heat which can not be restored to useful work.

The second law of thermodynamics is also applicable for living systems. The living organisms are always carrying on innumerable chemical reactions and physical changes ail of which require transfer and transformation of energy. So, there is continuous dissipation of energy which brings about entropy. Entropy will lead to death of the living system unless, there is continuous supply of usable or free energy. The usable energy is obtained from environment
either directly from sunlight (as in autotrophs) or indirectly from food (as in heterotrophs or animals). Therefore living organisms can not live without environment from which they get free energy and overcome entropy.

Open System and Closed System

An open system is that where constant inflow of energy occurs in order to make up the loss. In closed system there is no exchange of energy with the surrounding

The living organisms represent open systems because there is constant in flow of materials On environment failing which they die. For example a living organism is Continuasly supplied puts such as oxygen, water, food energy and a variety of other materials. Simultaneously,there is an output of CO2, nitrogenous wastes, faecal matter, heat.

Steady State

Steady state is a state of dynamic equilibrium where the rate of input of energy and matter is equal to the rate of output. In living organisms the steady state is achieved because the amount of input is equal to its output. Wear and tear are counter balanced by repair and regeneration. Anabolic process (build up process) is equal to catabolic process (break down process). Any difficulty in maintaining steady state of the organism would lead to death. For example-the protein component of food after metabolism produces nitrogenous wastes which are removed by excretory system. In case of kidney failure, the steady state is disturbed,nitrogenous was tes accumulate and turn toxic leading to death of the organism. Therefore, as long as, the steady state is maintainea, the organism is heal and hearty


The word homeostasis or homoeostasis (Gk. homoeos = like; stasis = standing) was coined by cannon in 1932. The concept comes from steady state of living Organisms. the ability of the living organisms to maintain nearly constant favourable internal conditions despite changes in the surrounding, through a self regulatory mechanisms. AS the external environment is never constant, the maintenance of a steady state is not possible unless there is a self regulating system. All organisms have some capacity to maintain their internal conditions. As a result, the chemical reactions in their cells continue without interruption inspite of changes in external world. Such a self regulated system is said to be in a state of homeostasis. Homeostasis help the body cells to continue their metabolic activities at an optimal level known as physiological equilibrium. Homeostasis becomes possible due to coordinated cellular activities in multicellular organisms. Some examples can be cited to explain the operation of homeostasis.
(i) When some one comes from bright light and enters into a dark cinema hall, nothing is visible at first due to bleached condition of the rhodopsin. But within few seconds the regeneration of pigments adjusts the sight to dim light.
(ii) The normal rate of heart beat per minute is 72. But, when one runs up a flight of stairs the heart beats faster to speed up blood circulation so that the increased need of oxygen by the cells and tissues can be fulfilled. After some time of rest, the normal heart beat is restored.
(iii) After vigorous exercise, the body temperature rises. Then, there is profuse sweating and cooling of the body is done by evaporation. Again the normal temperature is restored.

(iv) A minor injury or mild infection heals up automatically with passage of time.
(v) Osmoregulatory function of contractile vacuole in fresh water Amoeba is an example of homeostasis.

The homeostatic mechanisms work through feedback system. Body has detectors to receive the stimulus of change, interpretors for evaluation and effectors for producing a response that brings about homeostasis. The examples of few feedback mechanisms can be cited.

(i) Soon after taking food, glucose level in blood increases due to digestion and absorption. Now pancreas is stimulated to produce insulin which converts glucose in
liver and muscle to glycogen. When glucose level falls in blood, pancreas secretes another hormone glucagon which hydrolyses glycogen of liver to form glucose. The glucose comes to blood and maintains the blood glucose level.
(ii) Thyroxine hormone from thyroid regulates metabolic rate of the body. Low level of thyroxine in blood is detected by hypothalamus of brain and secretes thyroid releasing factor. It stimulates pituitary to produce thyroid stimulatings hormone (TSH). Now TSH stimulates thyroid to release thyroxine. When excess thyroxine is present in blood, hypothalamus stops secreting the releasing factor. Hence TSH and thyroxine secretion are also held up.

Although homeostatic mechanisms are common to all living organisms, many of them are still difficult to understand. For example, we do not know what clicks cell division, what factors determine when cell division should stop ; how many time a cell divides in life time; how many cells of what kind shall be produced and many more. But one thing is clear that, homeostasis is not merely restricted to the cellular or tissue or individual level, it extends to population, community, ecosystem and biosphere level and contributes to balance in nature

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