Bioenergetics Flashcards
first law of thermodynamics
energy cannot be created or destroyed. total energy in system remains constant.
units for energy consumption/release
kCal: amount of heat energy needed to raise temp of 1 kg of water up 1C.
kJ: one columb-volt: convert enerty to electrical units
second law of thermodynamics
reactions proceed in disorderly fashion, contributing to entropy of system..
red-ox coupled rxn
oxidized: loss of electron
reduced = gain of electrons.
what does gibbs free energy measure?
free energy change of reaction (kJ)
negative = exergonic
positive = endergonic
actual dG affected by?
temp, concentration of substrates; concentration of products.
reduction potentials represent?
equimolar concentrations of reduced and oxidized forms of a molecule at equilibrium.
E (subscript)0 =?
measures tendency of molecule to gain/lose electrons relative to redox potential of hydrogen (Eh)
what happens if H2 and O2 are mixed together?
nothing without a catalyst.
spark or bacterial hydrogenase = make water.
electron transfer in exergonic + endergonic rxn
exer: electron from more (-) to more (+). catabolic
ender: e- from more (+) to more (-). anabolic.
most efficient e- acceptor? e- donor?
acceptor = O2; donor = H2 or organic carbon.
bacteria thrive when? fuel + oxidant =?
reduced fuel source and poewrful oxidant
if dG is negative = still make a living.
characteristics of enzymes
proteins; increase rate by lower activation energy, not transformed by rxn. holoenzymes are apoenzyme + cofactor (closely bonded prosthetic groups , or loose and detach)
specific binding sites.
mechanism of enzyme rxn
increase rate of reaction, do not alter its equilibrium or its standard free energy.
-> lower activation energy
how is activation energy lowered
bring cubstrates closer together in proper orientation, prosthetic groups enhance reactivity.