Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.

1. BIOENERGETICS
WELCOME TO BIOENERGETICS
Dr. N. Sannigrahi, Associate Professor,
Department of Botany, Nistarini college, Purulia(W.B)India

2. ENERGY-THE BEAUTY OF LIFE

3. SUN-SOURCES OF ALL ENERY

4. BIOENERGETICS-BASIC CONCEPT
• Energy is the ability to do any work irrespective to nature of the work.
• In biological world, a lot of works arte being done in the different levels at the cost of energy,
• The energy currency of cell is ATP and mostly it is formed by the oxidation of food through
respiration and it follows the laws of energy in all respect.
• Thermodynamics is the branch of physical chemistry deals with energy changes and Biochemical
Thermodynamics of Biochemical Energetic or Bioenergetics is the field of biochemistry
concerned with the transformation of energy and energy dynamics in the living cells. The
chemical reactions occurring in living beings are associated with the liberation of energy as the
reacting system moves from a higher to a lower energy level. As the biological systems are
isothermal, the heat energy can not use to drive the vital process-Synthesis, active transport, nerve
conduction, muscular contraction and other biological pathways.
– A+C→ B+D+Heat
– The conversion of metabolite A to metabolite B occurs with the release of energy. It is
coupled to another reaction where the energy is required to convert C to D

5. ENERGY FROM ABIOTIC TO BIOTIC

6. AEROBIC RESPIRATION

7. LAWS OF THERMODYNAMICS
• ENERGY CONCEPT:
• Energy is the capacity to do work
• Work=Force * Distance
• 1 .0 Calorie of heat energy= 4.185×107 ergs of mechanical energy
• 1 Kcal=1000 Cal
• The basic SI unit of energy is Joule(J) named after James Joule where 1 Joule=the amount of
energy required to apply a 1 Newton force over a distance of 1 metre.
• 1000 cal= 4.184 J
• One Calorie is standardized as the amount of heat energy needed to raise the temperature of 1 gm
of water from 15-16ºC
• During respiration 1 mol of glucose discharge -673 Kcal energy.

8. 1st LAW OF THERMODYNAMICS
• In Thermodynamics, the universe is the system plus surroundings. There are three laws of
thermodynamics plus a zeros law of which the first two laws govern the behaviour of all energy
of our universe and these can be applied to all biological systems to measure the heat energy
content and the chemical composition of a reaction at the beginning and at the end. The laws are
below:
• The First Law :The total amount of energy in the universe (System + Surroundings) remains
constant. Paraphrased, it says that energy can not be created or destroyed and this can be
expressed as below:
• ▲E=EB-EA=Q-W
• where E=Change in internal energy, EA= Energy of a system at the start of process, EB= Energy of
the system at the end of the process=Heat absorbed by the system, W=Work done by the system.

9. 2nd LAW OF THERMODYNAMICS
• The 2nd law states that it is impossible to construct a machine functioning in cycles which can
convert heat completely into equivalent amount of work without producing changes elsewhere.
The term 'functioning in cycles 'indicates that the machine must return exactly to its original stage
at regular stages so that it can operate continuously.
• All physical and chemical changes tend to proceed in such a direction that useful energy
undergoes irreversible degradation into a randomized form called Entropy. It comes to a stop at an
equilibrium point at which the entropy formed in the maximum possible under the existing
condition.
• Entropy: Entropy(S) is a type of energy which can not perform work and is usually equated with
the degree of randomness or rate of disorderliness of the system. Accordingly, greater the entropy,
more is the disorderliness. It may also be stated that all the real process are associated with an
increase in the entropy and constitute irreversible reactions. The change of the entropy of the
system is denoted as '▲S' used by Rudolf Clausius in 1851.

10. ENERGY, ENTROPY & RANDOMNESS-PICTORIAL VIEW

11. 2ND LAW OF THERMODYNAMICS
• If entropy increases, then the content of useful energy present in the system declines.
• The 2nd law of thermodynamics states that ' a process can occur spontaneously only if the sum of the
entropies of the system and surroundings increases i.e. the entropy of the universe always increases
until equilibrium is attained at which point of the entropy is the maximum possible under the
prevailing conditions of temperature and pressure.'
• ▲System + ▲Surroundings>0 for a spontaneous process
• The total entropy of the system must increase if a process is to occur spontaneously. However, the
entropy of a system may decrease even during spontaneous process , if the entropy of the surroundings
increases to such an extent that their sum (System + Surroundings) positive.
• The 2nd law states that the ultimate driving force of all chemical and physical process is the tendency
for the entropy of the universe to be maximised.

12. THIRD LAWS OF THERMODYNAMICS
• The law states that the entropy of a system approaches a constant value as the temperature approaches
absolute zero. i.e. 0 Kelvin. Here, the constant value(not necessarily zero) is called residual entropy of
the system. With the exception of non-crystalline solids for example glasses, the entropy of the system
at absolute zero temperature, is typically close to zero and is equally to the log of the multiplicity of
the quantum ground states. Thus, all perfect crystals of pure substances possess zero entropy at
absolute zero temperature. The entropy of each compound increases in temperature. The quantity is
measured in JK-1 mol-1(Joule/Kalvin/mole). This is also called Nernst law after the name of scientist, Nernst.
• In a word, the temperature of a system approaches absolute zero, its entropy become constant or the
change in entropy(▲s)is zero.
• Absolute zero, the coldest possible temperature is 0K/-273º C or -459.67º F
• If we increase the temperature of the 0 system internal energy, then ▲≠0

13. ENTROPY & POSSIBILITY
• Thus, the change in free energy of a reaction, ▲G depends on the change in internal energy and on the
change in entropy of the system. The ▲G is a valuable criteria i9n determining whether a reaction can
occur spontaneously. Thus,
• a. If ▲G is negative in sign, the reaction precedes spontaneously with loss of free energy. i.e. it is
exergonic. If, in addition, ▲G is of great magnitude, the reaction goes virtually to completion and is
essentially irreversible.
• If, however, ▲G is positive, the reaction precedes only if free energy can be gained i.e. it is
endergonic. If, in addition, ▲G is of high magnitude, the system is stable with little or no tendency for
a reaction to occur.
• If▲ G is zero, the reaction system is at equilibrium and is no net change takes place.
• With regard to free energy change, G of a reacting system two more points need to be emphasized:
• 1. First, the G of a reaction depends only on free energy of the products minus that of the reactants.
The G of a reaction is independent of the path of transformation.Obviouly, the mechanism of a
reaction has no effect on G.

14. EXPLANATION
• As an instance, the value of▲ G is the same for the oxidation of glucose to Co2 & H2O whether it
takes place by combustion or by the series of enzyme catalysed reactions.
• II. secondly, the value of ▲G provides no information about the rate of reaction. A negative ▲G
indicates that a reaction can occur spontaneously, but it does not signify that it will occur at a
perceptible rate's already pointed out, the rate of a reaction rather depends on the free energy of
activation(▲G) which is unrelated to ▲G.
• Let us take an example: C 6H 12O6+ 6O2→6CO 2+6H 2O
• ▲G=-686 cal/mol
• ▲H= -673cal/mol
• ▲S=▲H-▲G/T, ▲S= -673000-(-686,000)/298=44cal/deg(i.e. the entropy of the universe is
increased)

15. CONCEPT OF FREE ENERGY
• The energy which is free to do some useful work called free energy or
• It is the form of energy capable of doing work under conditions of constant temperature and pressure.
• The Gibbs free energy (G) of a system is a measure of the amount of usable energy (energy that can do
work) in that system. The change in Gibbs free energy during a reaction provides useful information
about the reaction's energetic and spontaneity (whether it can happen without added energy). We can
write out a simple definition of the change in Gibbs free energy as:
• ΔG=G final–G initial.
• In other words, ΔG is the change in free energy of a system as it goes from some initial state, such as
all reactants, to some other, final state, such as all products. This value tells us the maximum usable
energy released (or absorbed) in going from the initial to the final state. In addition, its sign (positive
or negative) tells us whether a reaction will occur spontaneously, that is, without added energy.

16. ENTHALPY, ENTROPY & TEMPERATURE
• ∆H is the enthalpy change. Enthalpy in biology refers to energy stored in bonds, and the change in
enthalpy is the difference in bond energies between the products and the reactants. A negative ∆H
means heat is released in going from reactants to products, while a positive ∆H means heat is
absorbed. (This interpretation of ∆H assumes constant pressure, which is a reasonable assumption
inside a living cell).
• ∆S is the entropy change of the system during the reaction. If ∆S is positive, the system becomes more
disordered during the reaction (for instance, when one large molecule splits into several smaller ones).
If ∆S is negative, it means the system becomes more ordered.
• Temperature (T) determines the relative impacts of the ∆S and ∆H terms on the overall free energy
change of the reaction. (The higher the temperature, the greater the impact of the ∆S term relative to
the ∆H term.) Note that temperature needs to be in Kelvin (K) here for the equation to work properly.

17. ATP-UNIVERSAL CURRENCY OF FREE ENERGY IN BIOLOGICAL SYSTEMS
 The living organisms require a continuous supply of energy for the following purposes-
 To synthesize macromolecules from simpler and smaller precursors,
 To transport molecules and ions across membrane against gradients,
 To perform mechanical work as muscle contraction and
 To ensure fidelity of information of transfer in the form of transformation molecules like DNA, RNA
etc.
 The free energy derived from physical environment,
 The photoptrophs obtain this energy by trapping light energy from sun while chemotrophs obtain by
the oxidation of foodstuffs,
 The free energy derived from autotrophs or chemotrophs is partly transferred into a special form
before it is used for biosynthesis, transport or other biological actions,
 ATP- the free energy play a central role in the transference of energy from exergonic to endergonic
processes in the cells
 The ATP during phosphorylation , some of the free energy is harnessed to make ATP from ADP and
inorganic phosphate (Pi),
 ATP then used much of its energy for different biological activities by dephosphorylation.

18. ATP IN CELL CYCLE

19. ATP-STRUCTURE

20. ENDERGONIC AND EXERGONIC REACTIONS
• A biochemical reaction is associated with change of free energy and on the basis of the reaction of free
energy change, the reactions are of two types-
• 1. ENDERGONIC REACTIONS- It is also called non-spontaneous reaction or unfavorable reactions
in which the standard free energy change is positive , where energy is absorbed or gained.
• The reacting system moves from a lower energy under constant temperature and pressure and the
standard free (Gibbs) energy (ΔG°) would be positive,
• Endergonic reactions are quite common in biochemistry specially cells like protein synthesis,
carbohydrate synthesis, Na/K + Pump, ATP synthesis, fatty acid synthesis etc. During ETC, ATP
molecules are synthesized from ADP and Pi with the utilization of free energy associated with positive
the following reaction---- ADP + Pi---------------→ATP, here ΔG∘′ = + 7.3 kcal/mol
• 2.EXERGONIC REACTIONS- Here . The change in free energy is negative and it is associated
with the loss of free energy. This type of reaction is called spontaneous of favorable under constant
temperature and pressure and the change in standard free energy ΔG∘′ would be negative,
• ΔG∘′ <0, the reactions like burring of coal or wood, oxidation of sugars in cellular respiration,
oxidation of fatty acids, degradation of proteins, breaking down of ATP to ADP and iP etc are some of
the examples; ATP---------→ADP +Pi, ΔG∘′ = -7.3 kcal/mol

21. EXOTHERMIC & ENDOTHERMIC REACTIONS

22. EXERGONIC & ENDERGONIC REACTION

23. EXAMPLES OF ENDERGONIC AND EXERGONIC REACTIONS

24. DIFFERENCE BETWEEN ENDERGONMIC & EXERGONIC REACTION
ENDERGONIC EXERGONIC
Type of reaction that has positive Gibbs free energy. Type of reaction that has negative Gibbs free energy
Gibbs free energy has positive value Gibbs free energy has negative value
The energy of the reactants is lower than the
products.
The energy of the reactants are higher than the products.
Energy is decreased. Energy is increased
Reactions are non-spontaneous. Reactions are spontaneous
Endothermic reactions are endergonic. Exothermic reactions are exergonic
Always require energy to begin the reactions Do not need energy to begin the reactions
Absorb energy from the surroundings Release energy to the surroundings
Protein synthesis, Carbohydrate synthesis, ATP
synthesis
Oxidation of sugar, fatty acids, ATP hydrolysis etc

25. COUPLED REACTIONS
• An endergonic reactions may be linked or coupled with another exergonic reactions,
• An exergonic reactions may be linked or coupled with another endergonic reactions,
• The energy released in an exergonic reaction may be utilized by another endergonic reaction or the
energy utilized in an endothermic reaction may be released in another exothermic reaction.
• This kind of reaction where sharing of the energy by the counterpart collectively called coupled
reaction.
• Let , the conversion of metabolite M to N is an exergonic reaction, then it can be coupled with another
endergonic reaction where O is converted to metabolite P. When both the reactions are coupled, at the
end of the reactions, energy may be liberated if the total energy level of the products N+O is lower
than the M+P as follows:
• M+O------→N+P
• In biological system, ATP serves as a source of energy for most of the endergonic reactions and it is
also synthesized in a number of exergonic reactions. Hence, ATP acts as an ideal agent for coupling
an endergonic reaction with an exergonic one. Due to this coupling, the free energy is easily
transferred from one system to other.

26. COUPLED REACTIONS

27. HOPE, YOU HAVE ENJOYED THE JOURNEY.THANKS A LOT

28. YOUR HAPPINESS, MY PLEASURE--------
• REFERENCES:
 Fundamentals of Biochemistry- Jain, Jain, Jain
 Biomolecules and Cell Biology-Arun Chandra Sahu
 principles of Biochemistry- A.L. Lehninger
 Concepts of Bioenergetics- L. Pesuner,
 Biochemistry- S.C. Rastogi
 Different WebPages for text
 Google for images and text.
 Disclaimer
This Presentation has been made in order to address the need of academic fraternity without any
financial interest