Metabolism and energetics basics Flashcards by Holly Deere

at what pH is ATP chemically stable

6-9

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hydrolysis of ATP

ATP -> ADP + Pi

ATP -> AMP + PPi

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which hydrolysis of ATP releases most energy and when does this occur

ATP -> AMP + PPi

energy crisis signal of cells; intense exercise

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Why is ATP hydrolysis so energetically favourable

relieves electrostatic repulsion between the phosphate groups
increased entropy; ΔS becomes more positive
released phosphate ions are hydrated
high energy bonds of the phosphate group

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what is the ΔG of ATP hydrolysis

-31 to -50 kJ/mole

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what is the group carrried in high-energy linkage of ATP

Phosphate

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what is the group carried in high-energy linkage of NADH, NADPH and FADH2

electrons and hydrogens

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what is the group carrie din high-energy linkage of Acetyl CoA

Acetyl group

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what is the group carried in high-energy linkage of carboxylated biotin

carboxyl group

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what is the group carried in high-energy linkage of S-adenosylmethionine

methyl group

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what is the group carried in high-energy linkage of uridine diphosphate glucose

glucose

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3 stages of catabolsim of sugars, FA and AA

glycolysis, beta-oxidation and transamination
TCA cycle
oxidative phosphorylation

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first law of thermodynamics

energy cannot be created or destroyed, but can be tranformed from one form to another

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thermodynamics =

study of energy transfer

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types of energy

chemical, potential, mechanical, heat etc

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another name for chemical bond energy

Enthalpy

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symbol for enthalpy

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energy when bonds are made =

energy is released

stronger the bond, more energy released

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energy when bonds are broken

energy is required

stronger the bond, more energy neeeded

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bond energy =

energy required or released during bond breaking and making

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energy change of a reaction

ΔH
the sum of energy used when bonds are broken during a reaction and released during the formation of the new bonds
ENTHALPY CHANGE

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negative ΔH

when heat is lost from the molecle and released to the surroundings = exothermic

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postive ΔH

when heat is taken up from the surroundings = endothermic

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which ΔH reactions are more likely to occur

negative ΔH aka exothermic

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do negative ΔH reactions occur

yes they are most likely to occur

do postive ΔH reactions occur

althugh less likely, some reactions with positive ΔH will occur becuase of the 2nd law of thermodynamics - ENTROPY

2nd law of thermodynamics

all processes must increase the entropy of the universe

symbol for entropy

what is entropy

S - level of disorder or nuber ways something can be arranged. All living things sturggles against the tendencay to disorder = increased entropy

what reactions are favourble in terms of entropy

reactions where entropy increases; positve ΔS

symbol for gibbs free energy change

ΔG

what is ΔG

Gibbs free energy change

purpose of gibbs free energy change

to determine whether a reaction can occur or not, considering both entropy and enthalpy.

equation for gibbs free energy change

ΔG = ΔH - TΔS

units of ΔG

kJ/mol

in terms of ΔG, when will a reaction occur spontaneously

when ΔG is negative aka exergonic reaction

in terms of ΔG, when will a reactin NOT occur spontaneously

when ΔG is postive aka endergonic

what is an endergonic reaction

when ΔG is postive - will not occur spontaneously

what is an exergonic reaction

when ΔG is negative - will occur sponatneousl y

is ΔG a fixed value for a reaction?

No -it will change as the reaction proceeds towards equilibrium

when is ΔG zero

at equilibrium

what is ΔG at equilibrium

zero

unit for temperature in ΔG

kelvin

conversion of degrees C to Kelvin

+ 273 | 25 degrees C = 298 K

what is 25 degrees C in kelvin

298K

what is standard free energy change

ΔG°’ - when concentration of all reactants and products is 1M - temperature is 25C/298K - pH = 7 (biological systems)

what is ΔG°’ like for reversible reactions compared to irreversibe reactions

ΔG°’ is much smaller (less negative) in reversible reactions, and so dependign on condtitions, the reaction can go either way. Irreversible reactions have more negative ΔG°’ and so only one direction is energetically favourable, regardless of condtions

Example of reversible reaction

G6P F6P G6P -> F6P In standard conditions, ΔG°’ +1.7kJ/mol and so forward reaction will not spontaneously occur BUT In cell condtions, ΔG°’ -2.5kJ/mol and so forward reaction occurs spontaneously

equation for relating ΔG to ΔG°’

ΔG = ΔG°’ + RT ln [AB] / [A][B] R = gas constant 8.314 T in kelvin ln = natural log

relating ΔG°’ to equilbrium constant

ΔG°’= - RT lnKa ΔG = ΔG°’ + RT ln [AB] / [A][B] at equilbirum, ΔG = 0 ΔG°’ = - RT ln [AB] / [A][B] KA = [AB] / [A][B] therefore ΔG°’= - RT lnKA

equilibrium constatn

KA = [AB]/[A][B]

How can energetially unfavourable reactions occur

by coupling them to favourable reactions

example of energetically unfavourable reaction that occurs by coupling

Glutamate + NH4+ -> glutamine + H20, ΔG°’ = +15kJ/mol ATP + H2O -> ADP + Pi + H+ = -30kJ/mol Glutamate + NH4+ + ATP -> glutamine + ADP + Pi ΔG°’ = + 15 + (-30) = -15kJ/mol = favourable

oxidising agent

substance that recieves electrons

reduction =

gain of electrons

reducing agent =

substance donating electrons

E°

redox potential

what is E°

the abilty of a carrier to donate electros to another electron acceptor molecule

symbol for redox potential

E°

where do electrons flow

from a carrier with a negative E° to a carrier with a more postive E°

what are E° relative to

2H+ + 2e- ⇄ H2 which is set at 0.00V

what is the movement of elctrons in relation to 2H+ + 2e- ⇄ H2 if the redox pair has a negative E°

electrons move from the reduced substanct (Mg) to the H+

what is the movement of elctrons in relation to 2H+ + 2e- ⇄ H2 if the redox pair has a positve E°

electrons move from the H2 to the oxidised substance (Mg2+)

half reactions

- half reaction with higher E° will act as the reduction reaction - half reaction with the lower E° will act as the oxidation reaction

which half reaction will be the oxidation reaction

with lower E°

which half reaction will be the reduction reaction

with higher E°

ΔE°’ =

reduction potention of reduction reaction - reduction potential of oxidation reaction

what is a spontaenous reaction in terms of ΔE°’

ΔE°’ is postive | spontaneous reactions occur downhill to create products containing less free energy than the reactants

condtions of ΔG°’ and ΔE°’ for a spontaneous reaction

``` ΔG°’ = negative ΔE°’ = positive ```

releating ΔG°’ to redox potentials

ΔG°’ = -n F ΔE°’ ``` n = number of electrons transferred F = faraday constant, 96485 J/V/mol ```