Thermodynamic laws describe the flows and interchanges of heat, energy and matter. Almost all chemical and biochemical processes are as a result of transformation of energy. Laws can provide important insights into metabolism and bioenergetics. The energy exchanges between the system and the surroundings balance each other. There is a hierarchy of energetics among organisms

1. BIOLOGICAL
THERMODYNAMICS
Presented by
Dr. B. Victor., Ph. D
Email : bonfiliusvictor@gmail.com
Blog: bonvictor.blogspot.com

2. Presentation outline
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Introduction
What is thermodynamics? Definition.
Energy and biological energy needs.
Classes of thermodynamic systems.
Law of conservation of energy-key concepts and
explanation.
Law of degradation of energy – key concepts and
explanation.
Concepts of free energy, entropy and enthalpy.
Summary.

3. Introduction
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All organisms require energy to stay alive.
Organisms are energy transformers.
Organisms take in energy and transduce it to
new forms.
All chemical reactions in cells involve energy
transformations.
For example green plants transform radiant
energy into chemical energy.
Humans are „energy parasites‟.

4. 
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Thermodynamics
• Thermodynamics is simply
the study of energy.
• The science deals with
energy in its various forms
and the conversion of one
form of energy into another

5. What is thermodynamics?
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Thermodynamics is the study of energy
transformations that occur in a collection of
matter.
Thermodynamics is concerned with the
storage, transformation and dissipation of
energy.
Cells store energy, they transform it and they
dissipate to drive unfavorable reactions.

6. Objectives of thermodynamics
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All chemical, physical and biological processes
are ultimately enabled and regulated by the
laws of thermodynamics.
 1.to
understand the relationship between quantities of
heat and work in biological systems.
 2.to understand the influence of energy changes in
biological phenomena.
 3. to predict the effect of temperature on a variety of
physico-chemical and biological phenomena in
systems at equilibrium. e.g. bioreactors.
 4.to understand the biochemical processes.

7. Biological perspective of
thermodynamics principles
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In living cells, thermodynamic changes are
essential for biological functions such as
growth, reproduction photosynthesis and
respiration.
Chemical : photosynthesis.
 Chemical Chemical : cellular respiration.
 Chemical Electrical : Nervous system.
 Chemical Mechanical : Muscles.
 Light

8. Cells need energy to do all their
work
Biological energy needs
To generate
and maintain
its structure
To generate
To generate concentration
all kinds of and electrical
gradients
movements
across cell
membranes
To maintain To generate
body
Light in some
temperature
animals

9. Bioenergetics
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Bioenergetics is the quantitative study of
energy transductions in living cells.
The „energy industry‟ (production, storage and
use of energy) is central to the economy of the
cell society.

10. Definition of energy
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Energy is defined as the ability to do work.
Organisms take in energy and transduce it to
new forms.
The flow of energy maintains order and life.

11. Basic types of energy
•Energy in
motion
•Stored
energy

12. Basic forms of energy

13. Forms of energy
Energy
Kinetic
energy
Potential
energy
Energy in
motion
Stored
energy
Light, heat, electric
power
Dam, battery
Wood, fossil fuels

14. Animals are open thermodynamic
systems
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The matter flowing into the living system
contains a high energy potential.
The matter flowing out of the system is at a
low energy potential.
The energy changes that occur between these
two mass flow events are used to perform
chemical and physical work processes.

15. Biological
energy
transformation
s
Energy can be
changed from one form
to another
Plants = Photosynthesis = Starch
• Light energy  Chemical energy
Nerve = Neurotransmission = impulse
• Chemical energy Electrical energy
Eye = Vision = image
• Light energy  Electrical energy
Muscle = movement=power
Chemical energy  Mechanical energy

16. What is a system?
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An assemblage of matter, which can interact
with energy is called a system.
A system is separated from its surroundings by
a boundary. E.g. an organism, a fermenter or a
test tube.
Syste
m
Surrounding
s
Boundary

17. Classes of thermodynamic
systems
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Based on the differentiation between flows of
energy and flow of matter across the system
boundary, thermodynamics distinguishes 3
types of systems:
 1.An
open system exchanges matter and energy
with its environment.
 2.A closed system exchanges only energy with its
environment.
 3.An isolated system exchanges neither matter
nor energy with its environment.

18. An isolated system
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An isolated system has boundary which is
impermeable to both matter and all forms of
energy.
It exchanges neither heat nor matter with its
surroundings.
An isolated system
System boundary

19. Closed system
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A closed system may accept heat from the
surroundings but there is no transfer of matter
between the system and its environment. E.g.
universe.
When heat flows out of the system, the energy
of the system decreases.
When heat flows in, the energy of the system
increases.
If the heat remains constant, it may be called
an isothermal system. e.g. bomb calorimeter.

20. Open system
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An open system is one which can exchange
both energy and matter with its surroundings.
Biological systems are open. E.g. living cells,
living things.
Earth is an open system.
Matter exchange
Open system
Energy exchange

21. The first law of thermodynamics
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Law of conservation of
energy – this law was put
forward by Robert Mayer in
1941.
The first law states that “
the total energy of a
system plus its
environment remains
constant”.
This law declares that “
energy is neither created
nor destroyed in the
universe and it allows to be
exchanged between a
system and its
surroundings”.

22. Key concepts of first law
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The sum of the energy before the conversion
is equal to the sum of the energy after
conversion.
The total quantity of energy in the universe
remains constant.
The energy conversion is never 100% efficient.
Ecological efficiencies vary from 1% to 56%
depending on organisms.
Some energy is wasted in increasing the
disorder or entropy.

23. Explanation of the first law
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Light is a form of energy. It can be transformed
in to work, heat or potential energy of
food, depending on the situation, but none of it
is destroyed.
Plants convert light energy from the sun into
high energy compounds that help to build cell
material.
When animals eat plants, their stomach and
intestines break down the compounds for
further use.

24. Free energy (∆G) concept
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Free energy refers to the amount of energy
available during a chemical reaction to do cellular
work.
The free energy concept was developed by
Willard Gibbs in 1870s.
The Gibbs free energy is a thermodynamic
quantity which can be used to determine, if a
reaction is spontaneous or not.
Gibbs free energy equation = ∆G=∆H -T∆S
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Where ∆G=Gibbs free energy in KJ
∆H=enthalpy change
T = temperature in Kelvin K =273+oC
∆S=entropy change (in KJ K -1)

25. Gibbs free energy
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The driving force of a chemical as two
components
∆H is the drive toward stability (enthalpy)
∆ S is the drive toward disorder (entropy)
∆ G is the net driving force of a chemical
reaction.
∆ G values depend upon temperature,
pressure and the concentration of the
reactants and products.
If ∆ G<0 = the reaction is spontaneous.
If ∆ G>0 = the reaction is non-spontaneous.

26. Significance of ∆G
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The sign ∆G is a predictive element.
- ∆G  reaction favorable
(exergonic, spontaneous)
+ ∆G  reaction not
favorable(endergonic, non-spontaneous).
∆G =0 reaction at equilibrium (no change).

27. Second law of thermodynamics
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Also called law of the
degradation of energy
or law of entropy.
This law was
developed in 1850s
by German Physicist
Rudolf Clausius.
This law states that “a
system and its
surroundings always
proceed to a state of
maximum disorder or
maximum entropy”.

28. Explanation of second law
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Living systems are ordered, while the natural
tendency of the universe is to move toward
systems of disorder with unavailable energy.
The second law is an important indicator of the
direction of the reaction.
All reactions proceed in a direction with
increase in entropy and decrease in free
energy.

29. Concept of entropy (∆ S)
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The word entropy (from the Greek entrope =
change ) is a measure of the unavailable energy
resulting from transformations
The term is used as a general index of the
molecular disorder associated with energy
degradation.
Second law implies that the entropy of the
universe is increasing because energy
conversions are not 100% efficient. i.e. some heat
is always released.
Second law also implies that if a particular system
becomes more ordered, its surroundings become
more disordered.

30. Concept of entropy (∆ S) -2
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Entropy =unavailable energy or molecular
disorder.
Entropy is the capacity factor for thermal energy.
It is a function of state.
It is a function of the degree of disorder in the
system.
„Entropy tends to increase‟ = a change to a more
disordered state at a molecular level.
„no process is 100% efficient‟
High S value = high degree of disorder in a
system.

31. Concept of enthalpy (∆H)
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Enthalpy is defined as a change in heat
content or heat of formation of a system.
The change in enthalpy is given by ∆H= ∆U +P
∆V
 Where
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∆U= internal energy change
P=pressure
V=volume
∆U= the change in internal energy of a system is
equal to the heat added to the system minus the work
done by the system.
∆U=Q - W
Where Q= heat added to the system
 W=work done by the system

32. Two types of biochemical
reactions
Exergonic reaction (catabolic
reactions)
Endergonic reaction (Anabolic
reactions)
∆G is negative
∆G is positive
∆H is less than zero
∆H is greater than zero
Increase in stability
Decrease in stability
Spontaneous
Non-spontaneous
Movement towards equilibrium
Movement away from equilibrium
Coupled to ATP formation
Coupled to ATP utilization
Catabolism
Anabolism

33. Summary
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Thermodynamic laws describe the flows and
interchanges of heat, energy and matter.
Almost all chemical and biochemical
processes are as a result of transformation of
energy.
Laws can provide important insights into
metabolism and bioenergetics.
The energy exchanges between the system
and the surroundings balance each other.
There is a hierarchy of energetics among
organisms:

34. About the presenter
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Dr. B.Victor is a highly experienced postgraduate
professor, recently retired from the reputed educational
institution - St. Xavier‟ s
College(Autonomous), Palayamkottai, India-627001.
He was the dean of sciences and assistant controller of
examinations.
He has more than 32 years of teaching and research
experience
He has taught a diversity of courses and published 45
research articles in reputed national and international
journals.
Send your comments to : bonfiliusvictor@gmail.com