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BIOCH 310 > Bioenergetics And Thermodynamics > Flashcards

Bioenergetics And Thermodynamics Flashcards

1
Q

how do u calculate change in free energy?

A
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2
Q

what determines the speed of a rxn?

A

activation energy

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3
Q

what does G tell us about the rate of the reaction?

A

NOTHING

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4
Q

why might adding heat to a rxn to speed it up not be smart?

A

it is non-specific

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5
Q

what is [s/p], pH, T and pressure at chemical standard conditions?

A

[ ] = 1M
PH = 0
T = 25 degrees C or 298 K
Pressure = 1atm

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6
Q

what does Keq and ΔG° measure?

A

the tendency for a rxn to proceed spontaneously

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7
Q

how do u calculate change in free energy of a rxn at eq?

A
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8
Q

where is a reaction proceeding from to?

A

from standard conditions to eq

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9
Q

what is [s/p], pH, T , [H2O] and [Mg2+] for biochemical standard conditions?

A

[s/p] = 1M
pH = 7
T = 25 degrees C or 298 K
[H2O] = 55.5M
Mg2+ = 1mM

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10
Q

if Keq > 1 what does this tell us abt the rxn?

A

(-) ΔG° = rxn will proceed forwards

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11
Q

if Keq < 1 what does this tell us abt the rxn ?

A

(+) ΔG° =rxn will proceed in the reverse

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12
Q

if Keq = 0 what does this tell us abt the rxn?

A

the rxn is at equilibrium ΔG° = 0

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13
Q

why is the Keq not used to determine actual free energy change?

A

becaused actual free energy change is rarely at equilibrium

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14
Q

what is the equation to determine actual free energy change

A
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15
Q

what does the actual free energy of a reaction depend on?

A

the [P] and [R]

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16
Q

what do we need to know in order to determine delta G’ at non-Eq conditions?

A

[ ] or ratios of P/R

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17
Q

what units must delta G’, R and T be in to use nernst equation?

A

Delta G’ = J/mol
R = J/mol -K
T = Kelvin

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18
Q

when can delta G’ at standard conditions be determined?

A

if you know [P/R] at equilibrium

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19
Q

what is needed for the energy released by an exergonic process to drive an endergonic process - and vice versa?

A

a common intermediate

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20
Q

what is the difference between direct and indirect coupling?

A

direct coupling uses the same enzyme to drive both reactions while indirect coupling uses 2 different enzymes

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21
Q

what is the delta G’ for the conversion of glucose to G6P (phosphorylation of glucose)?

A

~ -17 kj /mol

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22
Q

what is the delta G for the hydrolysis of ATP?

A

~ -30kj/mol

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23
Q

what is a common product of endergonic reactions that is also a common intermediate?

A

Pyrophosphate (PPi)

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24
Q

how much energy is released when breaking phosphoester bonds?

A

-16kj / molho

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25
Q

what makes ATP a metastable compound?

A

kinetically stable - high activation energy

thermodynamically unstable - high amount of energy released

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26
Q

what makes Mg2+ so important in metabolism?

A

Mg2+ and ATP have to bind together as a substrate
-Mg++ activates ATP

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27
Q

why is delta G for ATP hydrolysis only an estimate?

A

because it depends on [Mg++]

28
Q

what is the difference between a phosphate transfer and phosphorylation?

A

A phosphate transfer does not use Pi

29
Q

what makes substrate level phosphorylation important in metabolism?

A

O2 is not needed and it always generates an NTP
- ATP can be made without oxygen

30
Q

how much energy is released from the hydrolysis of phosphocreatine? what makes this so high?

A

-43kj / mol
- more than ATP due to it being a phosphagen (phosphoamide with a higher group transfer potential than ATP

30
Q

what does phosphocreatine react with to make ATP?
what is the by-product?

A

Phosphocreatine + ADP + H+ ———> Creatine + ATP

31
Q

what is the importance of creatine?

A

it boosts power output in anaerobic conditions
-repetitive high intensity

32
Q

How much energy is released from the hydrolysis of acetylCoA (thioester)? what are the bi-products

A

-31 kj / mol
-CoA-SH (co enzyme A) and a carboxylic acid

33
Q

how is an acyl group produced?

A

the removal of OH from an oxoacid (usually carboxylic acid)

34
Q

how is coenzyme A activated

A

attachment of acetate or an acyl group to form acyl CoA or Acetyl CoA

35
Q

what 3 way can the body generate ATP?

A

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

36
Q

what is the Adenylate Kinase reaction?

A

ADP + ADP –> ATP + AMP

37
Q

what are the products of adenylate kinase reaction?

A

AMP and ATP

38
Q

why is the production of AMP from the adenylate kinase reaction so important?

A

AMP activates AMP dependent kinase which turns ON catabolic pathways and OFF anabolic pathways

39
Q

what stimulates increases in AMP kinase?

A

changes in the ATP-to-AMP ratio, AMPK is activated and phosphorylates downstream targets to redirect metabolism towards increased catabolism and decreased anabolism

40
Q

how does AMP affect PFK-1?

A

AMP stimulates PFK-1, enhancing glycolysis and energy production when cellular energy is low

41
Q

how is the adenylate kinase reaction useful other than production of ATP from ADP?

A

Drives the reverse rxn to be able to convert AMP to ATP

42
Q

what is transphosphorylation? where is this specifically important?

A

the transfer of a phosphate from one nucleotide to another
-important in G proteins to convert GDP to GTP

43
Q

what enzyme is used in transphosphorylation?

A

Nucleoside diphosphate Kinase (NDK)

44
Q

how is the transfer of nucleotides in transphosphorylation achieved?

A

phosphate is added to the enzyme and then removed from the enzyme to a NDP
-ping pong rxn

45
Q

what enzyme would be used to catalyze this transphosphorylation?

A

ADK or Myokinase

46
Q

what is adenylate kinase also known as?

A

Myokinase

47
Q

What are the 3 stages of aerobic catabolism?

A

1) breakdown of C backbone to generate Acetyl-CoA and NADH/FADH

2) Citric Acid Cycle - breakdown of acetyl-CoA

3) Oxidative phosphorylation

48
Q

where should the electrons belong to when considering oxidation state?

A

the most EN atom

49
Q

what is the equation used to determine oxidation state of a carbon atom?

A

of valence (4) - # of lone pair electrons + assigned electrons

50
Q

what are assigned electrons and what does this largely depend on?

A

he electrons that are counted as belonging to an atom in a compound or ion
- depends on EN of the atom attached to Carbon

51
Q

what 4 ways can electrons be transferred?

A

1) as electrons
2) as hydrogen atoms
3) as hydride ion
4) direct combination with oxygen

52
Q

what are oxidoreductases?

A

Oxidoreductases are a class of enzymes that facilitate oxidation-reduction (redox) reactions, which involve the transfer of electrons between molecules

53
Q

what is oxygenase? how is it classified?

A

enzyme that oxidizes a substrate by transferring O2 to it
-mono-oxygenase, dioxygenase…etc (transfer of 1 or more O2)

54
Q

what is an oxidase?

A

an enzyme that catalyzes an Ox-red rxn involving O2 as an electron acceptor

55
Q

what is a dehydrogenase?

A

An enzyme that removes hydrogen + electrons

56
Q

what is the flow of electrons based on in redox rxns?

A

the affinity of a molecule for electrons

57
Q

what is oxidation typically synonymous with?

A

dehydrogenation

58
Q

what does NAD+ being a cosubstrate tell us about it’s binding?

A

it binds loosely

59
Q

what does FAD as a prosthetic group tell us about its binding

A

it binds tightly

60
Q

what absorbance peak can you expect to see NAD+ at?

A

1 peak ~260nm

61
Q

what absorbance peak can you expect to see NADH at?

A

2 peaks, one around 260nm and another around 340nm

62
Q

what enzyme converts lactate to pyruvate? what else does this rxn produce?

A

LDH
-converts NAD+ to NADH

63
Q

what does it mean if LDH is seen in blood?

A

NADH will appear and this can mean serious health issues such as heart attack

64
Q

what is the arbitrary standard of reduction potential?

A

the half reaction of hydrogen

2H+ +2e- <–> H2
0 volts at standard conditions

65
Q

what is the reduction potential of hydrogen at pH 7?

A

-0.421V

66
Q

what is the reduction potential of hydrogen at standard conditions?

A

0 volts

BIOCH 310 (13 decks)

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