SOME GENERAL TERM FREE ENERGY ENDERGONIC REACTION EXERGONIC REACTION ACTIVATION ENERGY DEFINITION TRANSITION STATE WHERE DOES ACTIVATION ENERGY COME FROM? DETERMINING THE ACTIVATION ENERGY THROUGH ARREHINIUS EQUATION EFFECTS OF TEMPERATURE ON ACTIVATION ENERGY NEGATIVE ACTIVATION ENERGY EFFECTS OF ENZYMES ON ACTIVATION ENERGY CONCLUSION REFERENCES

1. Presentation On
Activation energy in biological
systems
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. CONTENTS:-
 SOME GENERAL TERM
 FREE ENERGY
 ENDERGONIC REACTION
 EXERGONIC REACTION
 ACTIVATION ENERGY
 DEFINITION
 TRANSITION STATE
 WHERE DOES ACTIVATION ENERGY COME FROM?
 DETERMINING THE ACTIVATION ENERGY THROUGH
ARREHINIUS EQUATION
 EFFECTS OF TEMPERATURE ON ACTIVATION ENERGY
 NEGATIVE ACTIVATION ENERGY
 EFFECTS OF ENZYMES ON ACTIVATION ENERGY
 CONCLUSION
 REFERENCES

3. SOME GENERAL POINTS
 ENERGY:-
 It is defined as the capacity to do work,that is the capacity
to change or move something.
 THERMODYNAMICS:-
 It is a branch of science which deals with the study of
different forms of energy and the quantitative relationship
between them.
 FIRST LAW OF THERMODYNAMICS:-
 Energy can neither be created nor be destroyed .although it
may be converted from one form to another.the total
energy in the universe remain constant.

4. • EXAMPLE:-
• when electric current flows in heater ,it
becomes hot because energy of electrical
current changes into heat.
• SECOND LAW OF THERMODYNAMICS:-
• It tells about the direction of energy flow.
• The total entropy of the universe is
continuously increasing.
• ENTROPY:-
• It is state variable which measure disorder
of the system. denoted by S.

5. FREE ENERGY
 The term Gibbs free energy (G) was given by the
American chemist J.willard Gibbs,in 1878.according
to him,”The maximum amount of energy available to
a system during a process which can be converted
into a useful work”
 G = H-TS
 H=enthalpy
 T=temperature
 S=entropy
 Change in free energy: at constant temperature.

6. ENDERGONIC REACTION:-
 An endergonic reaction is a chemical
reaction in which the standard change in free
energy is positive, and energy is
absorbed..and it is thermodynamically non -
favarable

7. EXERGONIC REACTION
 An exergonic reaction is a chemical
reaction where the change in the Gibbs free
energy is negative,indicating a spontaneous
reaction. It means it is thermodynamically
favarable .

8. Activation
energy :-
 It is a term introduced in 1889 by the Swedish
scientist Svante Arrhenius that is defined as the
energy that must be overcome in order for
a chemical reaction to occur
 The minimum energy required to start a
chemical reaction. The activation energy of a
reaction is usually denoted by Ea, and given in
units of kilojoules per mole.

10. TRANSITION STATE:-
 Reactants ,when they are at the crest of the
energy hump and ready to be converted to
products,are said to be at the transition
state.
 The activation energy, Ea (on graph) is the
energy difference between the reactants and
the activated complex, also known as
transition state.

11. Where does the activation energy come from?
 In most cases, the activation energy is supplied by
thermal energy, either through intermoleculr
collisions or (in the case of thermal dissocation) by
thermal excitation of a bond-stretching vibration to a
sufficiently high quantum level.
 As products are formed, the activation energy is
returned in the form of vibrational energy which is
quickly degraded to heat.

12. DETERMINING THE ACTIVATION ENERGY:-
 Arrhenius equation :-The Arrhenius equation gives the
quantitative basis of the relationship between the
activation energy and the rate at which a reaction
proceeds. From the Arrhenius equation, the activation
energy can be expressed as,

13.  A is the frequency factor
 R is the universal gas constant,
 T is the temperature (in kelvins)
 k is the reaction rate coefficient
 While this equation suggests that the
activation energy is dependent on
temperature
 Thus, Ea can be evaluated from the
reaction rate coefficient at any
temperature

14. Effects of Temperature on Activation Energy
 As temperature increases, gas molecules' velocity also
increases (Kinetic Theory of Gas).
 Kinetic energy of molecules is directly proportional to
the velocity of the molecules (KE = 1/2 mv2)
 So, when temperature increases, KE also increases.
This means that as temperature increases, more
molecules will have higher KE, thus the fraction of
molecules that have high enough KE to exceed the
minimum energy needed for a reaction also increase.

15. Negative activation energy
 In some cases, rates of reaction decrease with
increasing temperature.
 Elementary reactions exhibiting these negative
activation energies are typically barrierless reactions, in
which the reaction proceeding relies on the capture of
the molecules in a potential well.
 Increasing the temperature leads to a reduced
probability of the colliding molecules capturing one
another expressed as a reaction cross section that
decreases with increasing temperature.
 Such a situation no longer leads itself to direct
interpretations as the height of a potential barrier.

16. ENERGY REQUIRED TO OVVERCOME
ENERGY BARRIER
 Alingment of reactive groups
 formation of transient unstable changes
 Bond rearrangements
 Other transformation.

17. Effects of Enzyme on Activation Energy:-
 Enzymes:-
 Definition : “Enzymes greatly inhance the rate of chemical
reaction without being consumed in the process “
 Enzymes are biologically-active highly specific protein
"catalysts" that lower activation energy requirement and
speed reaction .
 Enzymes can be extremely specific in terms of reaction
substrates and products.
 Enzymes catalyze reactions under mild conditions (e.g. pH
7.4, 37ºC).
Enzymes affect reaction rates ,not the equilibria.

18. Effect of a Catalyst on Activation Energy
o .

19. BINDING ENERGY
 The energy derived from enzyme -substrate
interaction is called binding energy.
 Binding energy is the major source of free
energy used by the enzymes to lower the
activation energy.
 Binding energy contributes to specificity as well
as to catalyses
 Enzymes complementary to the transition state
not to the substrate.

20. LOCK AND KYE AND INDUCED FIT
HYPOTHESIS
 Lock and key" model:
 Enzymes are very specific, and it was suggested by
the organic chemist Emil Fischer in 1894 that this was
because both the enzyme and the substrate possess
specific complementary geometric shapes that fit exactly
into one another
 it fails to explain the stabilization of the transition state
that enzymes achieve.
 INDUCED FIT MODEL:
 In 1958, Daniel Koshland suggested a modification to
the lock and key model: since enzymes are rather
flexible structures, the active site is continually reshaped
by interactions with the substrate as the substrate
interacts with the enzyme
 The active site continues to change until the substrate is
completely bound, at which point the final shape and
charge is determined

22. CONCLUSION:
 Activation of energy is EXTREMELY important in
chemical reactions!!!! Without activation of energy a
reaction could not occur---reactions NEED energy in
order to continue. That is where activation of energy
comes in--it is the input of energy in a chemical
reaction that allows the molecules to get close enough
to cause a rearrangement of bonds.

23. REFERENCES:
 Cell and molecular biology-gerald
karp
 Principle of biochemistry-David
L.Nelson ,Michael M Cox
 Net source: www.google .com

24. • THANK YOU