The document discusses biochemical thermodynamics and energy transformations that occur in living systems. It explains that biochemical thermodynamics deals with the energy changes in biochemical reactions and predicts whether processes are possible, while kinetics measures reaction rates. The first and second laws of thermodynamics are described, with the first law stating that energy cannot be created or destroyed, only converted between forms, and the second law stating that spontaneous reactions result in increased disorder. ATP is discussed as the major carrier of chemical energy in cells, with its hydrolysis being an exergonic reaction and synthesis being endergonic. Substrate-level phosphorylation and electron transport chain are described as mechanisms for generating ATP.

1. ( Part –I )

3. biochemical thermodynamics
Its deals with the study of energy changes in
biochemical reactions.
It is concerned with the initial & final states of
energy component of the reactants and not
the mechanism of chemical reactions.
In short, bioenergetics predicts if a process is
possible, whereas kinetics measures how fast
the reaction occurs.

4. ?

5. Energy
• Capacity to perform work

6. • The study of energy transformations
that occur in a collection of matter.
• Two Laws:
1. First Law of Thermodynamics
2. Second Law of Thermodynamics

7. First Law of Thermodynamics
• Energy cannot be created or
destroyed, but only converted to other
forms.
• This means that the amount of energy
in the universe is constant.

8. The First Law is not much help...
What prevents a melting ice cube from
spontaneously refreezing?
Why doesn’t water flow uphill?
Will L-alanine convert into D-alanine?
The energy of the system and its surrounds won’t
change.
If it does not occur, what is driving force?

9. The Second Law helps resolve
problem
Only those events that result in a net
increase in disorder will occur
spontaneously

10. Second Law of Thermodynamics
• All energy transformations are inefficient
because every reaction results in an
increase in entropy and the loss of usable
energy as heat.
• Entropy: the amount of disorder in a
system.

11. Stage 1
Stage of
hydrolysis
Polysaccharides,
are broken down to
glucose, Lipids (TG) is
hydrolysed to FFA &
glycerol.
Proteins are hydrolysed
to amino acids.

12. Foods
GLYCOLYSIS
CarbohydratesProteins Lipids
Amino acids Fatty acid &
glycerol
NADH + H+
NADH + H+
FADH2
O2
H2O
Glucose
Pyruvate
Acetyl CoA
CO2
CO2
PDH COMPLEX
Waste products
NH3
Stage 1
Stage of
hydrolysis
Preparatory
stage
Oxidative
stage
Stage 3
CO2
NADH + H+
KREBS CYCLE
e-
e-
e-
ETC

13. Energy
containing
nutrients
Carbohydrates
Fats
Proteins
Energy
Depleted
End products
CO2
H2O
NH3
Cell
macromolecules
Proteins
Polysaccharides
Lipids
Nucleic acids
Precursor
molecules
Amino acids
Sugars
Fatty acids
Nitrogenous bases
Catabolism
Anabolism
ATP + Pi
NADH+H+
NADPH+H+
FADH2
ADP + Pi
NAD+
NADP+
FAD

14. Free Energy Change
• Free energy (∆G)
– The energy actually available to do work (utilizable).
• Enthalpy (∆H)
– is a measure of the change in heat content of the
reactants, compared to products.
• Entropy (∆S)
– a change in the randomness or disorder of reactants
and products.
• The relation between these three…
∆G = ∆H - T∆S

15. &

16.  There is a loss of free energy.
 These are spontaneous reactions.
 The free energy change (∆G) is represented
by a negative sign.
 E.g. Hydrolysis of ATP.
ATP + H2O → ADP + P (∆G°= –7.3 Cal/mol)

17. Hydrolysis of ATP
Hydrolysis
(add water)
P P P
Adenosine triphosphate (ATP)
P P P+
Adenosine diphosphate (ADP)
(∆G°= –7.3 Cal/mol)

18. Endergonic Reactions
 Energy must be supplied to the reactants.
 These are non-spontaneous reactions.
 The free energy change (∆G) is represented by
a positive sign.
 E.g. Synthesis of ATP.
ADP + P → ATP + H2O (∆G°= +7.3 Cal/mol)

19. Dehydration of ADP
Dehydration synthesis
(remove water)
P P P
Adenosine triphosphate (ATP)
P P P+
Adenosine diphosphate (ADP)
(∆G°= +7.3 Cal/mol)

20.  But at equilibrium, it is zero (∆G = 0)
 The energy coupling occurs by coupling of
exergonic and endergonic reactions and
liberation of heat.

21. What Can Cells Do with Energy?
Cells use energy for:
–Chemical work
–Mechanical work
–Electrochemical work

23. ❖Substances which possess sufficient free
energy to liberate at least 7.3 kcal/mol at
pH 7.0 are termed as high-energy
compounds or energy rich compounds.
❖All the high-energy compounds, when
hydrolyzed liberate more energy than that
of ATP.
24

24. Standard free energy of hydrolysis of
some phosphorylated compounds

25. ATP
Major activities promoted by ATP:
-locomotion
-membrane transport
-signal transduction
-keeping materials in the cell
-nucleotide synthesis
• ATP is the principal carrier of chemical
energy in the cell!
• High Energy compounds.
• Go’ = -7.3 kcal/mol
26

26. THE GENERATION OF ATP
ATP is generated by the phosphorylation of
ADP

28. -
Substrate-level phosphorylation is the
transfer of a high-energy PO4- to ADP at the
expense of the energy of the substrate
without involving the electron transport chain.
The substrate has higher energy level than
the product, the surplus energy is used up for
ATP formation.

29. Substrate-level phosphorylation – transferring a phosphate directly to ADP
from another molecule
Example –
PEP + ADP → Pyruvate + ATP

30. Redox potential of a system is the electron
transfer potential E0
Oxidation being termed for the removal of
electrons.
Reduction for gain of electrons,
When a substance exists both in the reduced
state and in the oxidized state, the pair is
called a redox couple.

31. When a substance has lower affinity for
electrons than hydrogen, it has a negative
redox potential.
NADH, has a negative redox potential (–0.32 V )
If the substance has a positive redox potential,
it has a higher affinity for electrons than
hydrogen.
oxygen has a positive redox potential (+0.82 V)
In electron transport chain, the electrons flow
from electronegative potential (-0.32) to
electropositive potential (+ 0.82).

33. 34
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