Bioenergetics Flashcards
midterm 1
bioenergetics definition
describes the transfer and utilization of energy in biological systems, concerned with the initial and final energy states, not the rxn mechanism
system
all the reactants and products with a regard to a chemical rxn, the solvent, and immediate atmosphere
types of systems
isolated system: no exchange of matter or energy
closed system: exchanges energy but not matter
open system: exchanges both energy and matter
thermodynamics
study of energy and its effect on matter
1st law of thermodynamics
energy is conserved but can be converted from one form into another
2nd law of thermodynamics
all processes involving energy changes under a given set of conditions of temp and pressure, some energy is lost
entropy (S)
the randomness/disorder of the components of a chemical system
change of entropy (S)
max value at equilibrium
S positive randomness increases
S negative randomness decreases
enthalpy (H)
measurement of energy in a thermodynamic system equivalent to total heat content of the system
change of enthalpy (H)
reflects the number/kinds of chemical bonds and non-covalent interactions broken and formed during a rxn
H positive: heat is absorbed (endothermic/breaking bonds)
H negative: rxn releases heat (exothermic/making bonds)
thermodynamics in biological systems
all rxns comply to thermodynamics, and occur under physioloigcal conditions
potential energy -> heat, simpler metabolic products (increase S), or more complex macromolecules (decrease S)
coupled rxns
happens commonly in metabolic pathways, when biochemical rxns must consume energy to make them occur
Gibbs free energy (G)
free energy of a system is the portion of the total energy in a system that is available for useful work
-determines if rxn is favorable
change of free energy (G)
G=0 process is at equilibrium
negative G: favorable, exergonic, spontaneous
positive G: unfavorable, endergonic, non-spontaneous
free energy equation
(delta)G= (delta)H - T(delta)S
thermodynamic favorability depends on what
energy differences & conc. of [S] & [P]
transition state
a state of higher free energy than both the reactant and product
activation energy
the energy required to reach the “transition state” of the molecule
-decreased w/ catalysis
oxidation
loss of electrons
reduction
gain of electrons
redox reactions
electrons are transferred from the reductant to oxidant
redox reactions examples
NAD+ and FAD
NAD+ and FAD
important role in citric acid cycle
-reduced to NADH and FADH2
-subsequent e- donation liberates free energy
ATP role in free energy
exergonic processes are coupled to the formation of ATP
endergonic processes are coupled to the consumption of ATP
ATP
contains adenine, ribose, and a triphosphate group
energy carrier/energy transfer agent
ATP structure
adenosine linked by phosphoester bond followed by two phosphoanhydride bonds
ADP, AMP, ATP
large free energy change from ATP to ADP, small free energy change from ADP to AMP
ADP + Pi much more stable than ATP
why is ADP and AMP are more stable
ATP has four closely spaced negative charges w/ strong repulsion between them
more resonance with ADP than ATP
ionization
Mg 2+
ATP synthesis
requires energy, so utilizes processes with more negative G values
ATP exception
ATP hydrolysis isn’t kinetically favorable, so needs to an enzyme
