Bioenergetics Flashcards
Bioenergetics
- Study of how biological systems operate while obeying the laws of thermodynamics - Uses the change in Gibbs free energy (delta G) to determine energy changes at constant pressure and temperature - Delta G reflects the amount of work a reaction either can perform or requires - Delta G can be estimated for coupled electron loss (oxidation) and gain (reduction) reactions
Delta G formula
Delta G = Delta H - T(Delta)S - For any reaction in which A B at constant pressure and temperature
Units of Delta G
Kcal/mol or Kjoule/mol
Delta H
- The change in enthalpy (aka change in heat content) - Reflects changes in the number and types of chemical bonds and noncovalent interactions broken and formed during the reaction
Delta S
- Change in entropy; reflects changes in the system’s randomness - An increase in entropy = increase in disorder = decrease in Delta G - Creating order from disorder takes energy and increases Delta G - Units of Delta S are Kjoules/mol*Kalvin or Kcal/mol*Kalvin
If Delta G = 0
The reaction is at equilibrium; there is no net flow in either direction
Any reaction with a non-zero Delta G
Proceeds spontaneously to a lower free energy state
If Delta G is negative
- The reaction will proceed spontaneously in the direction written
- The reaction releases energy and is said to be exergonic
Exergonic Reactions
- Release energy
- Have a negative Delta G
If Delta G is positive
- The reaction will proceed spontaneously in the reverse direction
- The reactions required energy to proceed in the direction written and is endergonic
Endergonic Reactions
- Require energy to proceed in the direction written
- Have a positive Delta G
Delta G for any reaction depends on what variables?
- The nature of the reactants and products
- Concentration of reactants and products
- Temperature
- Pressure
- pH
Standard Free Energy Change (Delta G°)
The change in free energy at 25 degrees celcius with all reactants and products initially in their standard states
Biochemical Standard Free Energy Change (Delta G°’)
Indentical to Delta G° except pH is specified at being at 7.0
Free energy change for non-standard-state concentrations
At equilibrium when Delta G = 0, and [C][D]/[A][B] = Keq, and Delta G°’ = - RTLnKeq
Delta G°’ can established by determining Keq
Reaction rate is proprtional to what?
Delta G Double Dagger = Free activation energy
This is how enzymes work to speed up reactions, by lowing the free activation energy requried to reach the transitional state
Common uses of ATP, GTP, CTP, and UTP
- Adenosine triphosphate hydrolysis provides energy for cellular reactions
- GTP provides energy for protein synthesis and intracellular signalling
- CTP for phospholipid synthesis
- UTP for complex carbohydrate synthesis
Delta E°’ equation
Delta E°’ = E°’ (e- acceptor) - E°’ (e- donor)
Delta G°’ = -nF(Delta)E°’
n = number of electrons
F = faraday’s constant
What happens to ATP production if oxygen is not available?
- Most ATP production will cease since the energy from oxidation of fuels (electrons carried by NADH and FAD(2H)) cannot be transferred to oxygen
- Oxygen consumption is coupled to total body energy expenditure
Oxygen consumption in the body
- 90-95% of O2 consumption in the resting state is used as an electron receptor in the mitochondrial electron transport/respiratory chain
- 5-10% is required for non-mitochondrial oxidases and oxygenases and is not related to ATP sythesis
