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
do negative ΔH reactions occur
yes they are most likely to occur
26
do postive ΔH reactions occur
althugh less likely, some reactions with positive ΔH will occur becuase of the 2nd law of thermodynamics - ENTROPY
27
2nd law of thermodynamics
all processes must increase the entropy of the universe
28
symbol for entropy
S
29
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
30
what reactions are favourble in terms of entropy
reactions where entropy increases; positve ΔS
31
symbol for gibbs free energy change
ΔG
32
what is ΔG
Gibbs free energy change
33
purpose of gibbs free energy change
to determine whether a reaction can occur or not, considering both entropy and enthalpy.
34
equation for gibbs free energy change
ΔG = ΔH - TΔS
35
units of ΔG
kJ/mol
36
in terms of ΔG, when will a reaction occur spontaneously
when ΔG is negative aka exergonic reaction
37
in terms of ΔG, when will a reactin NOT occur spontaneously
when ΔG is postive aka endergonic
38
what is an endergonic reaction
when ΔG is postive - will not occur spontaneously
39
what is an exergonic reaction
when ΔG is negative - will occur sponatneousl y
40
is ΔG a fixed value for a reaction?
No -it will change as the reaction proceeds towards equilibrium
41
when is ΔG zero
at equilibrium
42
what is ΔG at equilibrium
zero
43
unit for temperature in ΔG
kelvin
44
conversion of degrees C to Kelvin
+ 273 | 25 degrees C = 298 K
45
what is 25 degrees C in kelvin
298K
46
what is standard free energy change
ΔG°’ - when concentration of all reactants and products is 1M - temperature is 25C/298K - pH = 7 (biological systems)
47
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
48
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
49
equation for relating ΔG to ΔG°’
ΔG = ΔG°’ + RT ln [AB] / [A][B] R = gas constant 8.314 T in kelvin ln = natural log
50
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
51
equilibrium constatn
KA = [AB]/[A][B]
52
How can energetially unfavourable reactions occur
by coupling them to favourable reactions
53
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
54
oxidising agent
substance that recieves electrons
55
reduction =
gain of electrons
56
reducing agent =
substance donating electrons
57
redox potential
58
what is E°
the abilty of a carrier to donate electros to another electron acceptor molecule
59
symbol for redox potential
60
where do electrons flow
from a carrier with a negative E° to a carrier with a more postive E°
61
what are E° relative to
2H+ + 2e- ⇄ H2 which is set at 0.00V
62
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+
63
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+)
64
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
65
which half reaction will be the oxidation reaction
with lower E°
66
which half reaction will be the reduction reaction
with higher E°
67
ΔE°’ =
reduction potention of reduction reaction - reduction potential of oxidation reaction
68
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
69
condtions of ΔG°’ and ΔE°’ for a spontaneous reaction
``` ΔG°’ = negative ΔE°’ = positive ```
70
releating ΔG°’ to redox potentials
ΔG°’ = -n F ΔE°’ ``` n = number of electrons transferred F = faraday constant, 96485 J/V/mol ```