Bioenergetics Flashcards
Define bioenergetics
The study of energy relationships and energy conversion in biological systems
What are the two laws of thermodynamics?
1- energy is neither created nor destroyed - Etotal =0
2- entrpy of universe oncreases
Increases in entropy or randomness is favourable
What are the two entropy decreasing processes?
Ananolism
Formation of cells
Formation of proteins, nucleic acid, carbohydrates (large molecules)
What are the two components of Gibbs energy ?
Heat energy change
Entropy change
A chemical reaction can be endergonic in two ways
If dG >0
Or
dGr<dGp
do you think getting a large - dG ensures and guarantees that the reaction will occur?
A reaction can be spontaneous, favoured but may not occur
This can be when the mechanism of reaction is absent eg if an enzyme for that reaction is absent
And the mechanism of reaction is independent of dG
What is one way our body or a bio system can recycle /use the energy released in an exergonic rxn?
Energy coupling
An exergonic rxn coupled with an endogenic rxn
Define dG dGo dGo’ and its conditions
dG= free energy change observed
dGo= free energy change at 1M and PH=0
dGo’ = free energy change at 1M and Ph=7
What is the Problem in the previous definition of the dG?
Very reaction involving H+ is defined PH=0 at [H] =1M
Describe the rxn of Keq , dG and the ratio of products: reactants
P:R = keq, dG=0 EQUILIBRIUM
P:R > Keq, dG>0 P—->R
P:R < keq, dG<0 R—-> P
What are the two equations of dG?
1-DG=dH - TdS
2- dG = dGo’+ RT ln [keq]
What is the formula of dGo’
dG= -RTln[keq]’
Write down the formula of keq using this equation
2A —> 5C
Keq= [P]/[R]
Keq= [([C]^5) / ([A]^2)]
Draw out the 4 ways electrons are transferred
Draw the conversion of lactate to pyruvate
Draw the conversion of succinate to fumarate
What is reduction potential
Reduction potential is the voltage required to pull away the electrons from an electron donor
+ and - reduction potential
+ means the electron donor has high affinity for electron (better oxidizing agent) then e accepter
So more energy required to get reduced
- vice versa
Electrons move from
Low affinity to high affinity
Low affinity ( low rp)- ocidized
High affinity (higher rp)- reduced
This flow of electrons do work
Write down the equation through which energy from glucose is released.
C6h12o6 + H2o —-> co2 + h20 + energy (2840kj)
The electron move from glucose ( oxidized to co2) to oxygen (reduced to water) through
Glycolysis , tricarboxylic acid cycle , and respiration
This multi steps yields more energy
Exergonic rxn
Write the equation of the reduction of nad and fad
Nadh + 2e+2h+ —-> nadh +h+
Fadh + 2e + 2h+ —-> fadh2
Nadh
Diffusible and used by many enzymes
Hydride ion
Need 1 H and 1e to reduce and 1 e to neutralize the charge therefore. Hydride ion
Derived from niacin / vit B )
Fad
Flavin nucleotides are tightly bound prothestic groups of flavoproteins
How can you measure RP? Draw the system and describe / explain
Through a voltmeter
Reference cell - hydrogen electrode, h2 at 103kpa(1atp) at equilibrium and 1m of h2 concentration
Test cell- 1m of species oxidized and reduced in redox rxn .
Direction of electron transfer if e was positive
The refrences is h2
If Rp was positive means that test has high affinity for e
So e move from h2 to test
Direction of e transfer if RP was negative
Test has less affinity for e
So e moves from test to h2
Equation for RP(Eo’) of redox reaction
DE(redox) = E(e acceptor) - E(donor)
Equation of dGo’ from Eo’
dGo’ = -n x faradays constant(9.61kj/mols) x Eo’
Positive Eo’ are favourable
How are reactions coupled
The p from atp is passed to the substrate
Raises free energy of subs
The substrate reacts with other
As it converts to product , the P is released and free energy comes down
What is the activation energy required for atp synthesis?
220kj
How much energy is release by the terminal phosphate. Atp to ADP
30.5
How does ATP retain and release this energy
More res structures of ADP + P then ATP , increase entropy , more favourable
The products solvate by water molecules favourable bonds formed - stabilizing the products more then subs
Relief of electrostatic repulsion
As soon as atp -> adp, ADP dissociates one more proton - spon rxn contributes to overall -dG of hydrolysis
How much energy is released by cleaving each P
Amp (pp)+ p = 33
Amp(p) + pp = 45.6
Pp— p+p = 20
What is another curency that can store and release a lot of energy ?
Thioester bond = not resonance stabilized and therefore store more G then o2 esters
