This document discusses bioenergetics, which describes how living organisms capture, transform, store, and utilize energy. It defines endergonic and exergonic reactions, and explains that ATP is used to transport energy in cells. When ATP is hydrolyzed, energy is released to power cellular work in an exergonic reaction. This hydrolysis is coupled to endergonic reactions through common intermediates like ATP to drive biochemical pathways.
2. RECALL:
Define Buffer and body fluid?
Body fluid compartments.
Difference between ECF and ICF.
Outlines of electrolytes.
Body buffer systems
Protein buffer system
Carbonic acid
Phosphate buffer system
What is homeostasis?
3. Learning Outcomes
Need of Energy for the Living Organisms
Thermodynamics
Bioenergetics
Types of energy reactions
Metabolism and its types
Three thermodynamics quantities
Cellular energy
Coupled reactions
4. The Energetics of life
A living cell is a dynamic structure. It grows, moves,
synthesize complex molecules, and it selectively shuttles
substances in and out and between membrane-bound
compartments.
All of this activity requires energy.
Every cell and every organism must obtain energy from its
surroundings and expend it as efficiently as possible.
5. Example:
Phototrophs gather radiant energy from sunlight.
CO2 + H2O Organic compounds +O2
(sunlight)
Animals use the chemical energy stored in plants or other
animals that they consume.
Organic compounds + O2 CO2 + H2O + Energy
6. Different forms of energy
Thermal energy (to maintain a constant body temperature).
Mechanical energy (helps to move and allow to do work)
Electrical energy (sends nerve impulses and fire signals to and
from our brains).
Chemical energy (stored in foods and in the body)
7. Think!
How much food a human being should eat to maintain his
health status?
Why does the brain consume energy even when resting?
Why is it important to maintain electrolyte balance in the
cells?
These questions can only be answered by understanding
the concept of BIOENERGETICS.
8. WHAT IS BIOENERGETICS?
Bioenergetics describe how living
organisms capture, transform,
store, and utilize energy.
The quantitative study of energy transformation
(changes from one form to another) in living
systems and organisms (THERMODYNAMICS).
10. Endergonic Reactions
Chemical reaction that requires a net
input of energy.
Photosynthesis
6CO2 + 6H2O C6H12O6 + 6O2
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SUN
photons
Light
Energy
(glucose)
11. Exergonic Reactions
Chemical reactions that releases energy
Cellular Respiration
C6H12O6 + 6O2 6CO2 + 6H2O+
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ATP
(glucose)
Energy
12. What is Metabolism?
The sum total of
the chemical
activities of all
cells.
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14. Catabolic Pathway
Metabolic reactions which release energy
(exergonic) by breaking down complex molecules in
simpler compounds
Cellular Respiration
C6H12O6 + 6O2 6CO2 + 6H2O +
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ATP
(glucose)
energy
15. Anabolic Pathway
Metabolic reactions, which consume energy
(endergonic), to build complicated molecules from
simpler compounds.
Photosynthesis
6CO2 + 6H2O C6H12O6 + 6O2
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SUN light
energy
(glucose)
16.
17. THERMODYNAMIC QUANTITIES
1. Gibbs free energy (G) and free-energy
change, ΔG.
2. Enthalpy (H) and Enthalpy change ΔH.
3. Entropy (S) and Entropy change ΔS.
18. GIBBS FREE ENERGY (G)
It expresses the amount of energy
capable of doing work during a reaction
at constant temperature and pressure.
Gibbs free energy tells us that whether
a reaction will be spontaneous or not.
19. If ΔG is –ve = the process or reaction is
spontaneous.
If ΔG is +ve = the process or reaction is
nonspontaneous
20. FREE-ENERGY CHANGE (ΔG)
It is the change in free energy and the
direction of a reaction at any specified
concentration of products and reactants.
21. STANDARD FREE ENERGY CHANGE
(ΔG°)
ΔG° (with the superscript “o”)- energy
change when reactants and products are
at a concentration of 1 mol/L. (under
standard conditions).
The concentration of protons is assumed to be 10-7
mol/L, that is, pH = 7.
22. NEGATIVE ΔG (Exergonic reaction )
ΔG is negative when reactants
have more energy that products
then there is a net loss of energy.
The reaction goes spontaneously
because they can occur without
the addition of energy.
23. POSITIVE ΔG(Endergonic reactions):
ΔG is positive when the products of
the reaction contain more free
energy than the reactants.
There is a net gain of energy.
The reaction does not go
spontaneously from B to A
Energy must be added to the
system to proceed the reaction
from B to A.
24. ΔG IS ZERO:
oThe reactants and products are in
equilibrium.
When a reaction is proceeding spontaneously that is, free
energy is being lost then the reaction continues until ΔG
reaches zero and equilibrium is established
25. ΔG OF THE FORWARD AND BACK REACTIONS
The free energy of the forward reaction
(A → B) is equal in magnitude but opposite
in sign to that of the back reaction (B → A).
Example: If ΔG of the forward reaction is −5
kcal/mol, then that of the back reaction is +5
kcal/mol
26. ΔG depends on the concentration of reactants
and products
The ΔG of the reaction A → B depends on
the concentration of the reactant and
product.
27. •ΔG° = Standard free energy change
•R = Gas constant (1.987 cal/mol K)
•T =Absolute temperature (K)
•ln= Natural logarithm
•[A] and [B] = Actual concentrations of the reactant
and product
At constant temperature and pressure, the
following relationship can be derived:
28. NON-EQUILIBRIUM CONDITION:
The concentration of reactant is high
compared with the concentration of
product,
• Thus, the reaction can proceed in the
forward direction.
Example: glucose 6-phosphate is high in conc.
than fructose 6-phosphate.
29. Relationship between ΔGo and Keq:
In a reaction A → B, a point of equilibrium is reached
at which no further net chemical change takes place.
That is, when A is being converted to B as fast as B is
being converted to A.
31. ΔG°of two consecutive reactions are additive:
The standard free energy changes (ΔG°) are additive in
any sequence of consecutive reactions, as are the free
energy changes (ΔG).
32. ΔGs of a pathway are additive:
This additive property of free energy
changes is very important in biochemical
pathways through which substrates must
pass in a particular direction.
Example: A → B → C → D → ...)
34. ENTHALPY (H):
It is the heat content of the reaction
system.
It reflects the number and kinds of chemical
bonds in the reactants and products.
35. ENTHALPY CHANGE (ΔH)
The amount of heat evolved or absorbed in a reaction carried out at
constant pressure.
When a chemical reaction releases heat, it is said to be
exothermic(combustion) while when it absorbs heat, it is called
endothermic reaction(photosynthesis).
CH4 + 2O2 CO2 + 2H2O + heat
36. Negative and positive Enthalpy change ΔH
A negative enthalpy change represents an exothermic
change where energy is released from the reaction.
A positive enthalpy change represents an endothermic reaction
where energy is taken in from the surroundings.
The units of ΔH is joules/mole or calories/mole
37. Entropy
Entropy= disorder
2nd law of thermodynamics states: The entropy in a system and its
surroundings, must always increase. (the entropy of the universe is
always increasing.
Within a system there is always tendency to go higher entropy.
Entropy is not directly the measure of energy itself but it tells how
energy is distributed within a system.
More energy dispersal =more entropy
38. Example:
Solid state Liquid state
Lower entropy Greater entropy
More ordered More disordered
39. ENTROPY CHANGE (ΔS)
When the products of a reaction are less complex and
more disordered than the reactants, the reaction is said
to proceed with a gain in entropy.
42. What is cellular energy?
Our bodies contain trillions of cells. Inside
each of them are huge numbers of
tiny, energy-producing power plants called
“mitochondria”.
Mitochondria convert the food we eat and the
air we breathe into “ATP”, a special type of
fuel that powers our cells, and in turn, us.
43. ATP
Components:
1. adenine: nitrogenous base
2. ribose: five carbon sugar
3.phosphate group: chain of 3
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ribose
adenine
P P P
phosphate group
44. Adenosine Triphosphate
Three phosphate
groups-(two with
high energy bonds
Last phosphate
group (PO4) contains
the MOST energy
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45. ADP + PO4 + energy ----> ATP
ATP ----> ADP + energy + PO4
46. Breaking the Bonds of ATP
Occurs continually in
cells
Enzyme ATP-ase can
weaken & break last PO4
bond releasing energy &
free PO4
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47. How Much ATP Do Cells Use?
It is estimated that
each cell will generate
and consume
approximately
10,000,000 molecules
of ATP per second
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48. Reactions are coupled through
common intermediates
Two chemical reactions have a common
intermediate when they occur sequentially
so that the product of the first reaction is a
substrate for the second
49. Coupled Reaction - ATP
The exergonic hydrolysis of
ATP is coupled with the
endergonic dehydration
process by transferring a
phosphate group to another
molecule.
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H2O
H2O
50. Hydrolysis of ATP
ATP + H2O ADP + P (exergonic)
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Hydrolysis
(add water)
P P P
Adenosine triphosphate (ATP)
P P P
+
Adenosine diphosphate (ADP)
52. Formation of ATP
ADP + P ATP + H2O
(endergonic)
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P P P
Adenosine triphosphate (ATP)
P P P
+
Adenosine diphosphate (ADP)
Dehydration
(Remove H2O
53. Energy carried by ATP
If one phosphate is removed, ADP is
produced;
If two phosphates are removed, adenosine
monophosphate (AMP) results.
The standard free energy of hydrolysis of ATP,
ΔGo, is approximately –7.3 kcal/mol for each of
the two terminal phosphate groups.
54. Standard free energy of hydrolysis
of some important compounds :
Compounds ∆Go (Cal/mol)
High – Energy Phosphates
Phosphoenol pyruvate - 14.8
Carbamoyl phosphate - 12.3
Cyclic AMP - 12.0
1,3 – Bisphosphoglycerate - 11.8
Phosphocreatine - 10.3
Acetyl phosphate - 10.3
S – Adenosylmethionine - 10.0
Pyrophosphate - 8.0
Acetyl CoA - 7.7
ATP→ADP + Pi - 7.3
55. Standard free energy of hydrolysis
of some important compounds:
Compounds ∆Go (Cal/mol)
Low energy compounds
ADP→AMP + Pi - 6.6
Glucose 1-Phosphate - 5.0
Fructose 6-Phosphate - 3.8
Glucose 6-Phosphate - 3.3
Glycerol 3-Phosphate - 2.2
