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.
factors that affect enzyme activity
pH, temp. = must be optimal. short rang eof optimum.
what is competitive inhibition
enzymes bind substrates with similar structure. some drugs target this way to inhibit enzyme. concentration of inhibitory or natural substrate increases that substrate binding.
allosteric regulation = 3 key points
effector binds to inhibit/promote alternate substrate binding.
effector binds reversibly. causes conformational changes in catalytic site.
positve.negative effector
positive cause binding of substrate + catalysis.
negative - prevents substrate binding
feedback inhibition of sequential reaction
end product is negative modulator. inhibits first enzyme.
feedback inhibition : branched reaction
products inhibit first enzyme that makes their product. inhibit self, other path not affected.
covalent modification
reversible addition of chemical group to activate or inhibit enzyme activity. in equilibrium of other forms of enzyme.
