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BIOL 2421 - Cellular Biochem > 13. Bioenergetics > Flashcards

13. Bioenergetics Flashcards

1
Q

what is bioenergetics

A

the quantitative analysis of the capture, transformation, storage, and utilization of energy in organisms

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2
Q

state the first law of thermodynamics

A

for any physical change, the total amount of energy in the universe remains constant

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3
Q

state the second law of thermodynamics

A

the universe always tends towards disorder (entropy)

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4
Q

what is enthalpy

A

the heat content of a reacting system. It reflects the number and kinds of chemical bonds in the reactants and products

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5
Q

what are the units for enthalpy

A

Joules/mol

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6
Q

what variable is used for enthalpy

A

delta H

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7
Q

what is negative enthalpy

A

the reaction releases heat (exothermic)

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8
Q

what is positive enthalpy

A

the reaction requires heat input (endothermic)

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9
Q

what is entropy

A

the quantitative expression for the randomness/disorder in a system

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10
Q

what are the units for entropy

A

Joules/mol x Kelvin

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11
Q

what is variable is used for entropy

A

delta S

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12
Q

what is negative entropy

A

products are less disordered; loss of entropy

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13
Q

what is positive entropy

A

products are more disordered; gain of entropy

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14
Q

what is gibbs free energy

A

the amounts of energy capable of doing work

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15
Q

what variable is used for gibbs free energy

A

delta G

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16
Q

what is negative gibbs free energy

A

energy is released from the system (exergonic)

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17
Q

what is positive gibbs free energy

A

energy is gained by the system (endergonic)

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18
Q

what equation is used to relate G H and S

A

deltaG = deltaH - TdeltaS

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19
Q

what is the gas constant (R)

A

R=8.315 J/mol x K

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20
Q

describe the rates of a reaction at equilibrium

A

the forward and reverse rates are equal

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21
Q

describe the concentrations of reactants and products at equilibrium

A

the reactants and products have a specific, constant concentration

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22
Q

T or F: at equilibrium, there will be no further net change in the system

A

true

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23
Q

what does Keq measure

A

measures the ratio of products to reactants at equilibrium

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24
Q

describe the composition of a reacting system not at equilibrium

A

the composition will change until equilibrium is reached

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25
Q

how can we measure the magnitude of a driving force towards equilibrium for a reaction not at equilibrium

A

delta G

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26
Q

what does delta G close to zero mean

A

closer to zero= closer to equilibrium

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27
Q

what is ∆G’o

A

the biochemical standard free energy under the conditions of: pH 7, 1M, 25 degrees C, and 1 atm

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28
Q

T or F: ∆G’o is constant for each chemical reaction

A

true

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29
Q

T or F: ∆G’o and K’eq are heavily linked

A

true

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30
Q

describe the relationship between ∆G’o and K’eq when ∆G’o is negative

A

when it’s negative, the products have less free energy than the reactions, making the reaction spontaneous. Therefore the products are favored, so we have a large Keq

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31
Q

what equation connects ∆G’o and K’eq

A

∆G’o = -RTlnK’eq

where T is temp in Kelvin, and R is the gas constant

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32
Q

T or F: small changes in ∆G’o produce large changes in K’eq

A

true; for each tenfold change in Keq, the delta G only increases by 5.7 kJ/mol

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33
Q

describe the amount of standard free energy produced in hydrolysis of acid anhydrides

A

hydrolysis of acid anhydrides produces large decreases in standard free energy as compared to hydrolysis of other compounds

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34
Q

how is ∆G different from ∆G’o

A

∆G is the actual free energy change in GIVEN cellular conditions, not STANDARD cellular conditions

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35
Q

what equation links ∆G and ∆G’o

A

∆G=∆G’o + RTln(Q)

36
Q

what is Q

A

known as the mass action ratio. It’s the ratio of products over reactants

37
Q

why do we use Q instead of Keq

A

because Keq is only at equilibrium

38
Q

what are the units of Q

A

ALWAYS M (must convert to M before plugging into the equation)

39
Q

describe the relationship between ∆G and ∆G’o when: [reactant]=[product]

A

they’re equal

40
Q

describe the relationship between ∆G and ∆G’o when: [reactant]>[product]

A

∆G is smaller than ∆G’o

41
Q

describe the relationship between ∆G and ∆G’o when: [reactant]

A

∆G is larger than ∆G’o

42
Q

ln(1)=

A

0

43
Q

ln(fraction)=

A

negative number

44
Q

ln(integer)=

A

positive number

45
Q

what are the two different driving forces for a reaction

A

enthalpy and entropy

46
Q

describe an enthalpy driven reaction

A

delta S is negative (more order produced), delta H is negative (very exothermic), then delta G is also negative

47
Q

describe an entropy driven reaction

A

if delta H is positive (endo.) but delta S is very positive, then delta G can still be negative

48
Q

T or F: in reactions near equilibrium, Q and Keq are very far apart

A

false; they’re near each other

49
Q

describe the size of delta G absolute value when the reaction is near equilibrium

A

the absolute value of delta G is small

50
Q

T or F: near equilibrium, free energy changes are small and the reactions are easily reversible

A

true

51
Q

T or F: near equilibrium, the direction of the reaction can switch easily

A

true

52
Q

T or F: at reactions far from equilibrium, Q and Keq are very close together

A

false; Q and Keq are very far apart

53
Q

describe the size of delta G when the reaction is far from equilibrium

A

the delta G absolute value is very large

54
Q

T or F: far from equilibrium, free energy changes are large so the reactions are not easily reversible

A

true

55
Q

how are reactions far from equilibrium regulated

A

regulated by modulation of enzyme activity

56
Q

describe ΔG’o in a sequential reaction

A

each reaction has its own characteristic standard free energy: ΔG’o1 and ΔG’o2. These are additive

57
Q

T or F: the standard free energy values for a sequential reaction are additive

A

true

58
Q

what does the additive nature of gibbs free energies in sequential reactions explain

A

explains how a thermodynamically unfavorable reaction (+ΔG) can be driven in the forward direction by coupling it to a highly exergonic reaction (large -ΔG) through a shared intermediate

59
Q

in coupling/sequential reactions, what is often the shared intermediate

A

Pi or H2O

60
Q

what are many cellular reactions coupled to

A

the highly exergonic ATP hydrolysis reaction

61
Q

state the ATP hydrolysis formula

A

ATP + H2O = ADP + Pi + H

62
Q

describe the ATP turnover rate

A

the turnover rate in our body is HUGE because we go through so much ATP so we need to generate a bunch as well

63
Q

describe the linkage types in nucleoside triphosphates

A

one phosphate ester and two phosphoanhydrides

64
Q

in nucleoside triphosphate, describe the phosphate ester

A

its formed by a linkage of the a-phosphoryl group to the 5’-oxygen of ribose

65
Q

in nucleoside triphosphate, describe the two phosphoanhydrides

A

they’re formed by the a/B and B/y linkages between phosphoryl groups

66
Q

what is the charge on ATP

A

very negatively charged

67
Q

what is the role of Mg2+ in ATP

A

the positive charge stabilizes ATP by shielding some of the negative charges (either in aqueous solution or in the active site of enzymes)

68
Q

list the 3 reasons large amount is energy is released during ATP hydrolysis

A
  • electrostatic repulsion between neg charged O’s of phosphoanhydride groups is less after hydrolysis
  • hydrolysis products are better solvated than ATP itself
  • resonance stabilization of the product inorganic phosphate (Pi)
69
Q

T or F: we can assume ∆G is actually more negative than ∆G°’

A

true

70
Q

when talking about ATP hydrolysis, what value do we use for ∆G°’

A

-30.5 kJ/mol

71
Q

what does it mean to have a large negative ∆G’o

A

there’s lots of energy being held, and when cleaved the energy is released. The products are stabilized

72
Q

what is PEP

A

phosphoenol pyruvate

73
Q

how are the products of PEP hydrolysis stabilized

A

there are two possible constitutional isomers

74
Q

what is 1,3BPG

A

1,3-bisphosphoglycerate

75
Q

how are the products of BPG hydrolysis stabilized

A

ionization and resonance

76
Q

how are the products of phosphocreatine hydrolysis stabilized

A

resonance

77
Q

how are the products of thioesters hydrolysis stabilized

A

resonance

78
Q

what is acetyl CoA

A

a thioester

79
Q

which molecules have their hydrolysis products stabilized by alleviation of electrostatic repulsion

A

ATP

80
Q

which molecules have their hydrolysis products stabilized by ionization

A

ATP, BPG, thioesters

81
Q

which molecules have their hydrolysis products stabilized by resonance

A

ATP, BPG, thioesters, phosphocreatine

82
Q

which molecules have their hydrolysis products stabilized by isomerization

A

PEP

83
Q

how do BPG, PEP, and phosphocreatine interact with ADP

A

they’re all able to phosphorylate ADP into ATP

84
Q

which molecules are able to synthesize ATP

A

BPG, PEP, phosphocreatine

85
Q

why does a lot of biochemistry involve phosphorylation

A

to increase the free energy of that compound so that the compound has more free energy to give up in subsequent reactions. Phosphorylation primes the compound for future catabolic reactions

86
Q

why is it important that ATP have an intermediate level of delta G’o and not a super negative or small negative value?

A

ATP can carry energy from a high energy phosphoryl group donor produced by catabolism (ie PEP) to a low energy phosphoryl acceptor compound (ie glucose)

This converts the low energy compound into a more reactive species with better leaving groups

BIOL 2421 - Cellular Biochem (21 decks)

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