Bioenergetics And Thermodynamics Flashcards
how do u calculate change in free energy?
what determines the speed of a rxn?
activation energy
what does G tell us about the rate of the reaction?
NOTHING
why might adding heat to a rxn to speed it up not be smart?
it is non-specific
what is [s/p], pH, T and pressure at chemical standard conditions?
[ ] = 1M
PH = 0
T = 25 degrees C or 298 K
Pressure = 1atm
what does Keq and ΔG° measure?
the tendency for a rxn to proceed spontaneously
how do u calculate change in free energy of a rxn at eq?
where is a reaction proceeding from to?
from standard conditions to eq
what is [s/p], pH, T , [H2O] and [Mg2+] for biochemical standard conditions?
[s/p] = 1M
pH = 7
T = 25 degrees C or 298 K
[H2O] = 55.5M
Mg2+ = 1mM
if Keq > 1 what does this tell us abt the rxn?
(-) ΔG° = rxn will proceed forwards
if Keq < 1 what does this tell us abt the rxn ?
(+) ΔG° =rxn will proceed in the reverse
if Keq = 0 what does this tell us abt the rxn?
the rxn is at equilibrium ΔG° = 0
why is the Keq not used to determine actual free energy change?
becaused actual free energy change is rarely at equilibrium
what is the equation to determine actual free energy change
what does the actual free energy of a reaction depend on?
the [P] and [R]
what do we need to know in order to determine delta G’ at non-Eq conditions?
[ ] or ratios of P/R
what units must delta G’, R and T be in to use nernst equation?
Delta G’ = J/mol
R = J/mol -K
T = Kelvin
when can delta G’ at standard conditions be determined?
if you know [P/R] at equilibrium
what is needed for the energy released by an exergonic process to drive an endergonic process - and vice versa?
a common intermediate
what is the difference between direct and indirect coupling?
direct coupling uses the same enzyme to drive both reactions while indirect coupling uses 2 different enzymes
what is the delta G’ for the conversion of glucose to G6P (phosphorylation of glucose)?
~ -17 kj /mol
what is the delta G for the hydrolysis of ATP?
~ -30kj/mol
what is a common product of endergonic reactions that is also a common intermediate?
Pyrophosphate (PPi)
how much energy is released when breaking phosphoester bonds?
-16kj / molho
what makes ATP a metastable compound?
kinetically stable - high activation energy
thermodynamically unstable - high amount of energy released
what makes Mg2+ so important in metabolism?
Mg2+ and ATP have to bind together as a substrate
-Mg++ activates ATP
why is delta G for ATP hydrolysis only an estimate?
because it depends on [Mg++]
what is the difference between a phosphate transfer and phosphorylation?
A phosphate transfer does not use Pi
what makes substrate level phosphorylation important in metabolism?
O2 is not needed and it always generates an NTP
- ATP can be made without oxygen
how much energy is released from the hydrolysis of phosphocreatine? what makes this so high?
-43kj / mol
- more than ATP due to it being a phosphagen (phosphoamide with a higher group transfer potential than ATP
what does phosphocreatine react with to make ATP?
what is the by-product?
Phosphocreatine + ADP + H+ ———> Creatine + ATP
what is the importance of creatine?
it boosts power output in anaerobic conditions
-repetitive high intensity
How much energy is released from the hydrolysis of acetylCoA (thioester)? what are the bi-products
-31 kj / mol
-CoA-SH (co enzyme A) and a carboxylic acid
how is an acyl group produced?
the removal of OH from an oxoacid (usually carboxylic acid)
how is coenzyme A activated
attachment of acetate or an acyl group to form acyl CoA or Acetyl CoA
what 3 way can the body generate ATP?
1) oxidative phosphorylation - phosphorylation of ADP to ATP coupled to ETC
2) Substrate-level phosphorylation- direct transfer of phosphate group
3) ADK reaction ( adenylate kinase) synthesizes ATP from 2 ADP
what is the Adenylate Kinase reaction?
ADP + ADP –> ATP + AMP
what are the products of adenylate kinase reaction?
AMP and ATP
why is the production of AMP from the adenylate kinase reaction so important?
AMP activates AMP dependent kinase which turns ON catabolic pathways and OFF anabolic pathways
what stimulates increases in AMP kinase?
changes in the ATP-to-AMP ratio, AMPK is activated and phosphorylates downstream targets to redirect metabolism towards increased catabolism and decreased anabolism
how does AMP affect PFK-1?
AMP stimulates PFK-1, enhancing glycolysis and energy production when cellular energy is low
how is the adenylate kinase reaction useful other than production of ATP from ADP?
Drives the reverse rxn to be able to convert AMP to ATP
what is transphosphorylation? where is this specifically important?
the transfer of a phosphate from one nucleotide to another
-important in G proteins to convert GDP to GTP
what enzyme is used in transphosphorylation?
Nucleoside diphosphate Kinase (NDK)
how is the transfer of nucleotides in transphosphorylation achieved?
phosphate is added to the enzyme and then removed from the enzyme to a NDP
-ping pong rxn
what enzyme would be used to catalyze this transphosphorylation?
ADK or Myokinase
what is adenylate kinase also known as?
Myokinase
What are the 3 stages of aerobic catabolism?
1) breakdown of C backbone to generate Acetyl-CoA and NADH/FADH
2) Citric Acid Cycle - breakdown of acetyl-CoA
3) Oxidative phosphorylation
where should the electrons belong to when considering oxidation state?
the most EN atom
what is the equation used to determine oxidation state of a carbon atom?
of valence (4) - # of lone pair electrons + assigned electrons
what are assigned electrons and what does this largely depend on?
he electrons that are counted as belonging to an atom in a compound or ion
- depends on EN of the atom attached to Carbon
what 4 ways can electrons be transferred?
1) as electrons
2) as hydrogen atoms
3) as hydride ion
4) direct combination with oxygen
what are oxidoreductases?
Oxidoreductases are a class of enzymes that facilitate oxidation-reduction (redox) reactions, which involve the transfer of electrons between molecules
what is oxygenase? how is it classified?
enzyme that oxidizes a substrate by transferring O2 to it
-mono-oxygenase, dioxygenase…etc (transfer of 1 or more O2)
what is an oxidase?
an enzyme that catalyzes an Ox-red rxn involving O2 as an electron acceptor
what is a dehydrogenase?
An enzyme that removes hydrogen + electrons
what is the flow of electrons based on in redox rxns?
the affinity of a molecule for electrons
what is oxidation typically synonymous with?
dehydrogenation
what does NAD+ being a cosubstrate tell us about it’s binding?
it binds loosely
what does FAD as a prosthetic group tell us about its binding
it binds tightly
what absorbance peak can you expect to see NAD+ at?
1 peak ~260nm
what absorbance peak can you expect to see NADH at?
2 peaks, one around 260nm and another around 340nm
what enzyme converts lactate to pyruvate? what else does this rxn produce?
LDH
-converts NAD+ to NADH
what does it mean if LDH is seen in blood?
NADH will appear and this can mean serious health issues such as heart attack
what is the arbitrary standard of reduction potential?
the half reaction of hydrogen
2H+ +2e- <–> H2
0 volts at standard conditions
what is the reduction potential of hydrogen at pH 7?
-0.421V
what is the reduction potential of hydrogen at standard conditions?
0 volts
