Biochem Final Bioenergetics Flashcards
autotrophs vs. heterotrophs
autotrophs: produce their own high energy molecules
heterotrophs: require nutrients to produce high energy molecules
bioenergetics definition
quantitative study of energy transduction in living cells and of the nature and function of chemical processes underlying transductions
obeying law of thermodynamics
∆S positive vs negative
Entropy = S (J/mol x K)
+∆S = entropy increases
-∆S = entropy has decreased
∆S is relative
H definition
∆H definitions +/-
enthalpy - heat content of a system
- ∆H (J/mol) = heat release from system (exothermic)
+ ∆H = heat absorbed by system (endothermic)
∆G definition
Gibbs free energy - amount of energy capable of doing work during a reaction at a constant temperature and pressure
∆G (J/mol)
Gives direction of reaction and equilibrium position
-∆G = spontaneous reaction going forward, exergonic
+∆G = non-spontaneous moving forward, endergonic
∆G=0 at equilibrium
∆G is negative when either
∆S is positive (entropy increases) or ∆H is negative (exergonic)
when will ∆G be positive?
when ∆H is positive and and ∆S is negative
∆G^o1
standard free energy change at pH 7
how can thermodynamically unfavorable reactions be driven forward?
by coupling with a highly exergonic reaction through intermediate
summative ∆G^o1
Keq1 x Keq2
exergonic reaction of ATP
ATP to ADP, Pi (inorganic phosphate)
AMP to PPi
4 negative charges on phosphate groups repel each other (high energy)
phosphoanhydride bonds break by hydrolysis
non-ATP forms are more stable by resonance and better solvation
direct hydrolysis of ATP as source of energy for endergonic conformational changes
minority of cases
usually group transfer reaction: a transfer of phosphoryl, pyrophosphoryl or adenyl group to a substrate/enzyme to couple energy
energy to recreate ATP from ADP
derived from food in heterotrophs
derived from photosynthesis in autotrophs
enzymes that add or remove phosphates
kinase - adds phosphate
phosphatase - removes phosphate
forming phosphate esters
ATP often the donor of a phosphate to form phosphate ester like glucose-6-phosphate
how does specific binding sites facilitate ATP coupling of endergonic reactions?
substrates bind on specific enzyme sites which facilitate phosphorylation of substrate to catalyze endergonic reaction
glucokinase
type of hexokinase only present in the liver - phosphorylation enzyme of glucose molecules at the start of glycolysis
regulate the rate at which glucose is utilized in glycolysis (and amount of free glucose in the body)
lower energy positioning of electrons on reactants vs products
reactants share their electrons more equally than products which hold them more tightly, creating a lower potential
why are fuels chemically good energy sources?
reduced organic compounds from which electrons (and H+) can be stripped such as methane
the more reduced a carbon atom is, the more free energy there is to release upon oxidation (think fatty acid hydrocarbon tails)
how does ETC keep the electrons moving down
the electronegative oxygen is strong enough to attract electrons down a series of of electron acceptors
electron acceptors increase potential as electrons are received
standard reduction potential
E - measure in volts of electron affinity in flow of electrons
∆E^o’ = E^o’(e acceptor) - E^o’ (e donor)
NADH and FADH2 are
electron carriers, ready to shift form back and forth giving and receiving H+ and electrons
for ∆G to be negative, ∆E must be
positive
do you reverse the sign of ∆E^o’ when reaction direction is reversed?
NO, only with ∆G equations
redox reactions never involve
formation of free electrons
