Bioenergetics Flashcards
Anabolism vs catabolism. use/produce energy?
Anabolism: make macros. use Energy
Catabolism: break macros: produce E!
Energy transduction –> 3 steps
Photosynthesis –> cellular respiration –> biological work
Bioenergetics definition
quantitative study of energy transductions that occur in living cells/in nature
2 laws of thermodynamics
- conservation of energy; not created or destroyed but transformed. total energy remains constant
- all spontaneous processes of energy transformation increase entropy of universe
What do living systems do to maintain organization? (vs randomness of universe)
Extract useable energy from surroundings and release heat energy back into it
Entropy? units
degree of randomness. entropy change: J/mol*k
Enthalpy? reflects what? units
Heat content of system –> reflects number and kinds of chemical bonds in reactants and products
Units: J/mol or cal/mol
Gibbs free energy? Units. Formula
amount of energy capable of doing work during a reaction.
Units: J/mol
(delta)G = (delta)H - T(delta)S
negative vs positive deltaG
negative: reaction is favorable, spontaneous and moves forward –> exergonic
positive: rxn is unfavorable, not spontaneous, backwards –> endergonic
delta G = 0 –> (2)
equilibrium –> when rates of forward and reverse reactions are the same
positive S and negative H
spontaneous at all temp
positive S and positive H
spontaneous at high temp
negative S and negative H
spontaneous at low temp
negative S and positive H
not spontaneous. Spontaneous backwards
(delta)G’° –> what? formula? units?
(delta)G’° = -RT*ln(Keq)
Standard free E change at pH 7
J/mol or Kj/mol
Reverse reaction –> what happens to (delta)G and (delta)E
(delta)G –> change sign
(delta)E –> remains the same
(delta)G and (delta)E have _____________ relation! small change in (delta)G = ?
exponential
- big change in Keq
For a net reaction with multiple half reactions:
Standard free E changes ((delta)G) are ________ VS Keq’ are ___________
(delta)G –> additive
(Keq) –> multiplicative
How to drive forward a thermodynamically unfavorable reaction?
By coupling with a highly exergonic reaction through common intermediate!
ATP to ADP + Pi is exergonic or endergonic?
Highly exergonic = spontaneous
ATP structure (3)
Nitrogenous base (adenine) + ribose sugar + 3 PO4 groups bonded in series through phosphoanhydride bonds
Why does ATP have high potential E?
because of 4 negative charges in 3 phosphate groups that repel each other
Use of ATP’s energy: minority of cases vs more common
Minority: direct hydrolysis of ATP as energy source for endergonic conformational change
more common: transfer of Pi, PPi or adenyl group to a substrate or enzyme that couples energy of ATP breakdown to endergonic transformation of substances
ATP can be recreated from ADP –> how? heterotroph vs autotrophs
Endergonic reaction –> need energy derived from food in heterotrophs and light in autotrophs
Why is hydrolysis of ATP highly favorable under standard conditions?
- better charge separation in products –> relieves electrostatic repulsion of phosphate groups
- more favorable resonance stabilization of reactants (Pi) –> each of the 4 P-O bond have same degree of double bond
- higher degree of solvation of products –> less repulsion btw negative charges = better interaction with water
How does ATP drive endergonic reaction? (2)
- substrate bind to specific locations in enzyme (glucokinase, hexokinase)
- energy transferred during ATP hydrolysis is transferred to substrate by phosphorylation
2-step group transfer facilitates ATP dependent reactions (2)
- phosphoryl group transferred form ATP to glutamate
- phosphoryl group is displaced by ammonia and replaced as Pi
Redox reactions involve ?
electron transfer
Oxidation vs reduction
Oxidized = lose electron
reduced = gain electron
electron donor = ? agent and oxidized/reduced
reducing agent. and is oxidized
electron acceptor = ? agent and oxidized/reduced
oxidizing agent. is reduced
2 types of electron “movement”
- electrons transferred completely from one atom to another
- electrons shift their position in covalent bonds based on electronegativity of atoms
C-C, C-H vs C-O bonds. which has highest potential energy
C-C and C-H: same electronegativity –> high potential E because hold electrons less tightly (share equally)
C-O bonds: O is more negative, holds electrons more tightly –> lower potential E
Do carbs or FA or CO2 have more energy?
CO2 < Carbs < FA (bc more C-C and C-H bonds)
The more reduced carbon atom is , (more or less) free E is released upon oxidation
more
(CH4 has more energy than CO2)
most electron acceptors (lose/gain) potential energy as they are reduced
gain
electrons go from (more/less) energetic to (more/less energetic in ETC
less to more
Standard reduction potential (E) = ? Units?
measure of molecule’s affinity to electrons. in Volts
