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Metabolism > Metabolism and energetics basics > Flashcards

Metabolism and energetics basics Flashcards

1
Q

at what pH is ATP chemically stable

A

6-9

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2
Q

hydrolysis of ATP

A

ATP -> ADP + Pi

ATP -> AMP + PPi

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3
Q

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

A

ATP -> AMP + PPi

energy crisis signal of cells; intense exercise

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4
Q

Why is ATP hydrolysis so energetically favourable

A
  • 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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5
Q

what is the ΔG of ATP hydrolysis

A

-31 to -50 kJ/mole

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6
Q

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

A

Phosphate

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7
Q

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

A

electrons and hydrogens

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8
Q

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

A

Acetyl group

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9
Q

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

A

carboxyl group

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10
Q

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

A

methyl group

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11
Q

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

A

glucose

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12
Q

3 stages of catabolsim of sugars, FA and AA

A
  1. glycolysis, beta-oxidation and transamination
  2. TCA cycle
  3. oxidative phosphorylation
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13
Q

first law of thermodynamics

A

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

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14
Q

thermodynamics =

A

study of energy transfer

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15
Q

types of energy

A

chemical, potential, mechanical, heat etc

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16
Q

another name for chemical bond energy

A

Enthalpy

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17
Q

symbol for enthalpy

A

H

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18
Q

energy when bonds are made =

A

energy is released

stronger the bond, more energy released

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19
Q

energy when bonds are broken

A

energy is required

stronger the bond, more energy neeeded

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20
Q

bond energy =

A

energy required or released during bond breaking and making

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21
Q

energy change of a reaction

A

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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22
Q

negative ΔH

A

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

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23
Q

postive ΔH

A

when heat is taken up from the surroundings = endothermic

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24
Q

which ΔH reactions are more likely to occur

A

negative ΔH aka exothermic

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25
Q

do negative ΔH reactions occur

A

yes they are most likely to occur

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26
Q

do postive ΔH reactions occur

A

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

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27
Q

2nd law of thermodynamics

A

all processes must increase the entropy of the universe

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28
Q

symbol for entropy

A

S

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29
Q

what is entropy

A

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

30
Q

what reactions are favourble in terms of entropy

A

reactions where entropy increases; positve ΔS

31
Q

symbol for gibbs free energy change

A

ΔG

32
Q

what is ΔG

A

Gibbs free energy change

33
Q

purpose of gibbs free energy change

A

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

34
Q

equation for gibbs free energy change

A

ΔG = ΔH - TΔS

35
Q

units of ΔG

A

kJ/mol

36
Q

in terms of ΔG, when will a reaction occur spontaneously

A

when ΔG is negative aka exergonic reaction

37
Q

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

A

when ΔG is postive aka endergonic

38
Q

what is an endergonic reaction

A

when ΔG is postive - will not occur spontaneously

39
Q

what is an exergonic reaction

A

when ΔG is negative - will occur sponatneousl y

40
Q

is ΔG a fixed value for a reaction?

A

No -it will change as the reaction proceeds towards equilibrium

41
Q

when is ΔG zero

A

at equilibrium

42
Q

what is ΔG at equilibrium

A

zero

43
Q

unit for temperature in ΔG

A

kelvin

44
Q

conversion of degrees C to Kelvin

A

+ 273

25 degrees C = 298 K

45
Q

what is 25 degrees C in kelvin

A

298K

46
Q

what is standard free energy change

A

ΔG°’

  • when concentration of all reactants and products is 1M
  • temperature is 25C/298K
  • pH = 7 (biological systems)
47
Q

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

A

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

48
Q

Example of reversible reaction

A

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

49
Q

equation for relating ΔG to ΔG°’

A

ΔG = ΔG°’ + RT ln [AB] / [A][B]

R = gas constant 8.314
T in kelvin
ln = natural log

50
Q

relating ΔG°’ to equilbrium constant

A

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

51
Q

equilibrium constatn

A

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

52
Q

How can energetially unfavourable reactions occur

A

by coupling them to favourable reactions

53
Q

example of energetically unfavourable reaction that occurs by coupling

A

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

54
Q

oxidising agent

A

substance that recieves electrons

55
Q

reduction =

A

gain of electrons

56
Q

reducing agent =

A

substance donating electrons

57
Q

E°

A

redox potential

58
Q

what is E°

A

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

59
Q

symbol for redox potential

A

E°

60
Q

where do electrons flow

A

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

61
Q

what are E° relative to

A

2H+ + 2e- ⇄ H2 which is set at 0.00V

62
Q

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

A

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

63
Q

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

A

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

64
Q

half reactions

A
  • half reaction with higher E° will act as the reduction reaction
  • half reaction with the lower E° will act as the oxidation reaction
65
Q

which half reaction will be the oxidation reaction

A

with lower E°

66
Q

which half reaction will be the reduction reaction

A

with higher E°

67
Q

ΔE°’ =

A

reduction potention of reduction reaction - reduction potential of oxidation reaction

68
Q

what is a spontaenous reaction in terms of ΔE°’

A

ΔE°’ is postive

spontaneous reactions occur downhill to create products containing less free energy than the reactants

69
Q

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

A 
ΔG°’ = negative
ΔE°’ = positive
70
Q

releating ΔG°’ to redox potentials

A

ΔG°’ = -n F ΔE°’

n = number of electrons transferred
F = faraday constant, 96485 J/V/mol

Metabolism (11 decks)

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