Bioenergetics Flashcards
(25 cards)
What are the two laws of thermodynamics?
1: energy cannot be created nor destroyed
2: entropy of the universe is always increasing and randomness increases are favourable
What is the equation for ∆G?
∆G = ∆H - T∆S
∆G’º = -RTlnKeq (use J and K!)
What is the difference between an spontaneous and nonspontaneous reaction?
Spontaneous: ∆G is NEGATIVE (exergonic)
Nonspontaneous: ∆G is POSITIVE (endergonic)
what is energy coupling?
Energy released from spontaneous exergonic reactions are used to fuel nonspontaneous endergonic reactions.
What is the standard state? What about the physiological standard state?
Standard: 1 atm, 25ºC, 1M solute, ph = 0
Standard physio: 1atm, 25C, 1M solute, ph = 7
What is the difference between oxidation and reduction?
Oxidation: Loss of electron
Reduction: Gain of electron
What is the pathway for a redox couple?
- donor = e- + acceptor
- AH2 = A + 2e- + 2H+
- AH2 + B = A + BH2
- 2RCH3 + O = 2RCH2OH
What is the standard reduction potential?
Voltage needed to pull electrons away from the donor of the redox couple.
Low tendency = high affinity = +ve Eº’
High tendency = low affinity = -ve Eº’
How does measuring standard reduction potential work?
- One cell has H2 = H+ and e-, and the other has a half reaction
- If the half reaction has a low affinity for its electrons, it will transfer them to the reference cell and give to the proton, voltage will be negative
- If the half reaction has a high affinity for its electrons, it will cause H2 to give its electrons to its reactants; voltage will be positive
How do you find the ∆G of a redox reaction?
∆G = -nF∆Eº
n = # of electrons exchanged per reaction
F = faraday’s constant, 96.1 kJ/Vmol
∆Eº = E(acceptor) - E(donor)
How do you find ∆Eº of a spontaneous reaction?
- Find which half reaction has a higher affinity for the electrons (+ve Eº value), and that will act as the acceptor, while the other will act as the donor.
- Set up the equation with proper direction and sum them.
- Calculate ∆Eº = Eº acceptor - Eº donor.
How is ATP hydrolysis used to convert Glu + NH3 = Gln?
- Phosphate from ATP is transferred to an enzyme or substrate which becomes activated
- Phosphorylation raises free energy of Glu so amidation is a downhill step
- Reaction is completed by displacement of phosphate (-30.5 + 14.2 = -16.3 kJ/mol)
How is glucose phosphorylated?
- ATP hydrolysis (-30.5 kJ/mol)
- glucose + Pi formation (+13.8)
- Net energy release = -16.7
Why doesn’t ATP spontaneously decompose?
The reaction is spontaneous (-30.5kJ/mol) but occurs very slowly due to the high activation energy (220kJ/mol) in the absence of enzymes.
Why is ATP a good source of energy currency?
- Hydrolysis of ATP allows relief of charge repulsion in condensed state
- There is more resonance between ADP + Pi than ATP
- Post hydrolysis ADP spontaneously releases one more proton which contributes to -ve ∆G’
- Hydrolysis products are solvated by water molecules which is a favourable interaction that stabilizes the products more than the reactants.
What are other compounds have large ∆G of hydrolysis values?
1,3 biphosphoglycerate to 3phosphoglycerate (-49 kJ/mol)
Phosphenolpyruvate to pyruvate (-62 kJ/mol)
Phosphocreatine to creatine (-43 kJ/mol)
What is substrate level phosphorylation?
ATP is produced by directly coupling its formation to an energy releasing reaction.
What is a high energy phosphate?
Gamma terminal of ATP, releases 30.5 kJ/mol
What is the difference between production of AMP from ADP and ATP?
ADP + H2O = AMP + Pi (-33kJ)
ATP + H2O = AMP + PPi (-45kJ + (-20 kJ) from PP)
What is a thiolester?
R−CO−S−R groups that are not resonance stabilized and store more G than oxygen esters. (-31.4 kJ/mol)
What is glycolysis?
10 enzyme catalyzed steps that transforms glucose into 2 molecules of pyruvate. Includes energy expenditure phase (cost 2 ATP) and energy payoff (production of 2 NADH and 4 ATP)
What is lactic acid fermentation?
Pyruvates are converted to lactate by lactate dehydrogenase and NADH
What is ethanol fermentation?
Yeast making ethanol from pyruvate and then oxidizes ethanol to acetaldehyde.
What is the warburg effect?
Tumour cells dramatically increase glucose uptake and glycolysis by increasing synthesis of hexokinase and glucose transporters.
