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Title: BIOENERGENETICS
Description: These are very good,simplified notes on bioenergetics for anyone pursuing a Bachelor's Degree in Biochemistry or Biology. I use these notes to lecture Biochemistry at the University of Zambia
Description: These are very good,simplified notes on bioenergetics for anyone pursuing a Bachelor's Degree in Biochemistry or Biology. I use these notes to lecture Biochemistry at the University of Zambia
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Bioenergetics 1
Quantitative study of energy
transductions
The nature & function of the chemical
processes
Biological energy transductions obey;
Thermodynamics Laws
...
Bioenergetics 2
For any physical or chemical change
total energy in the universe remains
constant
...
However, any change in the system
requires an equal & opposite change in
surroundings
Bioenergetics 3
In any spontaneous process entropy
increases
...
G is the maximum energy available for
useful work
...
Bioenergetics 4
Living organism are inter-dependant
exchanging energy matter via the
environment
...
Hydrolysis of ATP yields a large
amounts of free energy
ATP links metabolic pathways
...
This statement should bother people
...
It sure looks like energy is going up in
smoke
...
The universe can be viewed to be made
up of some user defined "system" and
everything else outside the "system"
which is identified as the
"surroundings"
...
The sum of the energy changes for the
universe must total zero
...
The two changes are equal in size but
opposite in sign
...
The two changes are mirror images of one
another
...
The only restriction is
that the two pieces system and
surroundings must add up to equal the
universe
...
Spontaneous Processes
Spontaneous process is a naturally occurring
process that once started will continue to
happen without outside intervention
...
A ball rolling
downhill is an example of a spontaneous
mechanical process
...
A burning
match is an example of a spontaneous
chemical change
...
A non spontaneous process only
happens when outside action introduces
energy to drive the process
...
A ball being rolled uphill is an example of a
non spontaneous mechanical process
...
Production of carbohydrates by plants is an
example of a non spontaneous chemical
change, photosynthesis needs light energy
...
High values for entropy, S, match high
amounts of disorder
...
Entropy 2
The two processes combine to yield an
increase in entropy
...
Entropy 3
The disorder you generated exceeds
the order you made
...
If you see a process that has an
increase in entropy it will usually be
spontaneous
...
Free Energy 1
An American physicist and chemist, J
...
Gibbs is not famous in the way Einstein
is but, he is as important to our
understanding of the laws governing
energy changes as Isaac Newton and
other notable scientists
...
This is the energy that can be used for a
specific purpose and is available from a
process
...
Free Energy 3
The term " ΔH" is defined as the
change in "enthalpy"
...
Typically this is a heat transfer
...
The term "T ΔS" is the energy used to
produce the entropy effects that
accompany the process
...
The "T" is the
temperature in Kelvin degrees
...
A system is at equilibrium & no net
change can take place if ΔG is zero
...
Predicting spontaneity 1
With –ΔG, the system releases energy to its
surroundings as the process occurs
...
The size of the free energy change indicates
the "driving force" behind the reaction
...
Predicting spontaneity 2
For instance, a reaction with a ΔG = 623,400 kcal has a better chance of
happening than a reaction with a ΔG = -500
kcal
...
Thus releasing the stored energy and
gradually the system reaches a stable
condition of equilibrium
...
Thus protein folding proceeds
spontaneously under appropriate
conditions
...
Graphite is more stable than
diamonds
...
the more stable form of carbon,
graphite, is more common
...
They are rare
...
The system must take in energy from
the surroundings for the process to
occur
...
Predicting spontaneity 6
The reactants are forced to change by
energy put into the system
...
If the system is given no additional energy
the process will stop
...
This is the attribute of catalysts
...
(Rusting of iron is
spontaneous and occurs gradually
...
Reacting systems have a tendency to
move to equilibrium
...
Application of free energy
states 2
The ΔGo of formation of a compound is
the difference between its G in standard
state & the total energies of its
elemental composition
...
For most solutes, the std states are
taken to be 1M solutions
...
However, in Biochemistry the std state
for hydrogen ion in solution is usually
defined as 10-7M solution
...
Std free energies of formation are
known for most compounds
...
By subtracting the sum of the G of
formation of the reactants from the sum
of the G of formation of products, the
ΔGo can be calculated
...
76
-113
...
62
-9
...
45
-164
...
49
Calculation of free energy
changes 1
Consider the equation:
Oxaloacetate2 + H+
CO2(g) +pyruvate
ΔGo =-113
...
45 – (-9
...
62)
= -7
...
However, some concentrations are not
realistic
...
We can add the std free energy change for
this reaction of: CO2 +H2O HCO3 + H+
The calculation thus yields a correction of 140
...
87 – (-56
...
45) = 0
...
4 + 0
...
6Kcal/mole
...
Energy Coupling 1
The central issue in energy coupling is the
means by which energy from metabolism or
light capture is coupled to energy requiring
processes
...
Chemical reactions can also be coupled with
energy releasing reaction driving energy
requiring ones
...
Thus no net change in both
components (steady state)
...
Thus releasing G which is then available
to do work (Exergonic)
Energy Coupling 3
In cells, Exergonic (G-ve) reactions can
be or are coupled to Endergonic (G+ve)
process to drive otherwise unfavorable
reactions
...
The product contains more energy than
reactants
Energy Coupling 4
A second exergonic reaction can occur
in living cells ATP
ADP + Pi
In this reaction the product contain less
energy
...
Reaction 2 is the Exergonic reaction
that drives many Endergonic reactions
...
The terminal phosphoryl group is
transferred to acceptors
...
As noticed already, an Exergonic
reaction does not necessarily proceed
rapidly
...
Enzymes in energy
metabolism 1
Dehydrogenase enzymes play a key role
in the oxidation of fuel containing
molecules
...
However, their action is limited by a
suitable acceptor of electrons for
reoxidation if oxygen is absent
...
Virtually every chemical reaction occurs at a
measurable rate only because of enzymes
...
This option is however not available in living
cells
...
Inactivation of cellular components can
occur
...
Enzymes in energy
metabolism 4
Catabolism ( degradation pathways)
free energy yielding
...
Metabolism is required to achieve
balance & economy
Title: BIOENERGENETICS
Description: These are very good,simplified notes on bioenergetics for anyone pursuing a Bachelor's Degree in Biochemistry or Biology. I use these notes to lecture Biochemistry at the University of Zambia
Description: These are very good,simplified notes on bioenergetics for anyone pursuing a Bachelor's Degree in Biochemistry or Biology. I use these notes to lecture Biochemistry at the University of Zambia