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Biochemistry > Bioenergetics L9, 11, 12 > Flashcards

Bioenergetics L9, 11, 12 Flashcards

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1
Q

what are some of the key characteristics of living matter

A

Structurally complicated/Highly organised
Extracts, transforms and uses energy from the environment
Capacity for self replication (reproduce) and self assembly

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2
Q

what is bioenergetics

A

describes how living systems capture, transform and use energy to perform work and stay alive

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3
Q

what are examples of biological work

A

synthetic
mechanical
concentration (active inward transport of molecules)
electrical work (active outward transport of ions)
heat
bioluminescent

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4
Q

what is hydrocarbon combustion

A

CH4 +2O2 –> 2H2O + CO2 +energy (usually heat)

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5
Q

how can energy be produced from carbohydrate and lipids

A

C6H12H6 + O2 —> 6CO2 +6H2O + energy

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6
Q

how do biochemists measure energy involved in metabolism

A

mostly use equilibrium thermodynamics

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7
Q

what is a system

A

matter within a defined region of space

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8
Q

what is an open system

A

energy an matter can move in and out system

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9
Q

what is a closed system

A

only energy can leave system

matter cannot leave system

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10
Q

what is an isolated system

A

neither energy or matter can leave the system

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11
Q

what is the concept of equilibrium thermodynamics

A

Study of heat exchange that occurs in a reaction that is closed system as reaction reaching equilibrium

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12
Q

what do biochemists mean by energy

A

usually the chemical energy that is exchanged in reactions

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13
Q

what happens in a steam engine in equilibrium thermodynamics

A

steam /heat converted to kinetic energy

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14
Q

what happens in a internal combustion engine

A

petrol, diesel etc chemical energy converted to kinetic energy

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15
Q

what is the biological piston engine - muscle fibre contraction

A

Biological engine
Muscle fibers made of thick and thin filaments, when contract they slide into each other
Thick – myosin act like ores (rowing a boat) , in cyclic fashion wind themselves in into thin filament
Convert chemical energy (ATP) to kinetic – muscle contraction

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16
Q

what is the first law of thermodynamics

A

Energy within a system is conserved, it can be changed from one form to another , but it cannot be created or destroyed
initial=end

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17
Q

what is the reaction equation that relates to the first law of thermodynamics

A 
ΔE = Q – W
ΔE = change in the ‘internal energy’ 
Q = heat added to cylinder
W = work done by piston
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18
Q

what is the equation that shows if a reaction occurs in well insulated container and no heat exchange

A

ΔE = Q – W

Q=0,
ΔE = E – W

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19
Q

if the piston is prevented from moving, there is no work done what is the equation

A

ΔE = Q – W

W=0
ΔE = Q

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20
Q

what is a bomb calorimeter function

A

most direct way of measuring the energy content of metabolites and food stuffs

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21
Q

what happens to the energy made from bomb calorimeter

A

energy produced by combusting or oxidizing a substrate can be measured as a change in internal energy, ΔE

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22
Q

what is the ΔE in an exothermic reaction

A

negative

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23
Q

how are metabolites energy content measured

A

Crucible add in substance want to measure
Placed in the steel bomb and sealed
Filled with pure oxygen 1 atm pressure ignited – fully combustion
Release of energy in form of heat
Heat exchanged to the water surrounding the steel bomb and the temperature change is measured by the thermometer
no energy added so ΔE= Q

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24
Q

what are the temperature differences between system and surrounding in living

A

living systems temperature differences between system and surroundings are small (10-20°C)

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25
what is the enthalpy of a system
measure of the heat change during a reaction at constant pressure and volume
26
how are enthalpy changes found
``` ΔE = ΔH – PΔV (E = internal energy, P = Pressure, V = volume) ```
27
what assumptions are made when calculating enthalphy
``` constant pressure (atmospheric) volume changes are negligible ```
28
what does ΔH ^O or ΔH^-O- mean
enthalpy changes under standard conditions | molar quantities, atmospheric pressure and 25OC (298K
29
what does a bomb calorimeter help us calculate
the energy produced in reactions
30
how is efficiency measured
energy out / energy in x 100
31
how does lactate form in sprinters
use fast muscle fibres to convert glucose to lactate
32
what forms from marathon runners
slow muscles to convert glucose and fat to carbon dioxide and water
33
what does the heart muscle convert
fatty acids to carbon dioxide and water
34
how efficient is the conversion of glucose to lactate
ΔH = - 50 kJmol-1 is only 1.8% efficient | Not all 50kJmol-1 used for cellular processes and metabolism
35
what does entropy mean
useless energy
36
what is free energy
energy available to drive biochemical reaction
37
what is the Gibbs-Helmholtz equation
ΔG° = ΔH° - TΔS°
38
what is ΔG° in the Gibbs-Helmholtz equation
Gibbs or free energy
39
what is ΔH° in the Gibbs-Helmholtz equation
Change in enthalpy
40
what is -T in Gibbs-Helmholtz equation
Absolute temperature (K)
41
what is ΔS° in the Gibbs-Helmholtz equation
Change in entropy
42
what does the Gibbs-Helmholtz equation relate to
Constant Pressure and Temperature
43
what is the concept of free energy and entropy
Water in reservoir has capacity to do useful work that drives turbines and make electricity (free energy) Water downstream lost capacity to make energy (entropy)
44
what is the second law of thermodynamics
free energy must be negative | entropy must be positive
45
what is the reaction if ΔG <0
reactants convert into products (forward reaction)
46
what is the reaction if ΔG >0
reverse reaction is favoured
47
what is the reaction if ΔG = 0
equilibrium
48
can biochemical pathways in metabolic pathways be reversed
thought of as irreversible as require energy to reverse
49
what is the probability of second law of thermodynamics
when energy under pressure / heated If remove 'barrier' energy will disperse itself within system/environment till reach thermal equilibrium Telling us what is more probable All go from less probable to a more probable reaction –drive biochemical reaction Require energy to reverse a reaction
50
which reaction is favoured
reaction with the higher entropy is more probable
51
where are free energy changes
Free energy changes are most easily obtained from studies of a reaction approaching equilibrium
52
``` what is the Gibbs free energy equation equilibrium constant (Keq) ```
ΔG° = - R.T. ln Keq
53
what does ΔG° mean in the Gibbs free energy equation
standard free energy change
54
what does R mean in the Gibbs free energy equation
gas constant (8.31 joule mol-1 K-1)
55
what does T mean in the Gibbs free energy equation
absolute temperature
56
what does ln mean in the Gibbs free energy equation
natural log
57
how can equilibrium constants be measured in biochemistry
``` often easy to measure equilibrium constants Lactic acid (‘lactate’) and pyruvic acid (‘pyruvate’) are readily interconverted in the liver ```
58
what is ΔG'
actual energy change
59
what is ΔG°'
standard energy change
60
what is most of a cells free energy used for
to synthesize proteins by creating peptide bonds
61
what are the energetics of peptide bond formation and protein synthesis
polyribosomes synthesise peptide bonds very efficiently - translation reaction must be ‘driven’ by hydrolysis of ATP & GTP free energy changes associated with ATP/GTP hydrolysis are more than enough to compensate for the unfavourable free energy changes associated with peptide bond formation
62
what is energy coupling
Overall ΔG° must be negative Free Energy must decrease and entropy must increase In theory 3 molecules of ATP/GTP are used for every peptide bond produced
63
what requires energy in animals
- creating cellular infrastructure - synthesis of amino acids - active transport of nutrients - ‘wasteful’ or ‘futile’ cycle of protein turnover
64
what are high energy phosphate bonds
Not energy in the bonds themselves – not the energy when break bonds Difficult to break bonds and release energy Big change in free energy from the initial state to final state
65
what are phosphate group transfers and ATP
ATP reactant, makes large changes in free energy Less probable to more probable Negative oxygen repel – unstable, wants to move and make it more stable – electrostatic repulsion Release of this charge by remove water Resonance stabilisation – become more stable Really unstable to more stable state – driving hydrolysis of ATP – get such large changes in energy (high energy phosphate bonds)
66
what are the origins of high energy phosphate bonds
1. Relief of charge/charge repulsion between phosphates | 2. Increased possibilities for resonance and delocalisation of electrons
67
what is the energy charge or a cell
ratio of ATP relative to ADP and AMP
68
how is ATP recharged
other coupling reactions
69
how is ATP re-synthesised
need to put in energy 30kJmol-1 Result of it being positive it must couple to something with a high negativity (phosphoenol pyruvate) uses pyruvate kinase, -52kJmol-1 Decrease in free energy as -22kJmol-1
70
what is the oxidation of carbohydrates and lipids
Glycolysis produces acetyl co-enzyme A, enters the Krebs cycle, produces CO2 and active hydrogens (NADH and FADH2)
71
what are the compounds used to produce more ATP
active hydrogen in NADH and FADH2
72
how is NAH reduced
In NAD has nicotine amide ring, substrate hydrolysed it releases a hydrogen and two electrons
73
what reaction occurs in transfer of hydrogen
electrons is redox
74
what happens in reduced coenzymes and electron transport
Co enzymes produce ATP and NADH High energy electrons – inactive hydrogen NADPH has extra phosphate – stimulated by light Active hydrogens transfer electrons to electron transport chain, produce further ATP
75
how are redox couple written
oxidised 'half couple 'on the left
76
how are standard reduction potentials generated
Reference cell (hydrogen ion [1M] equilibrated with hydrogen gas) is 0 volts Reference cell connected to an electrode via a voltmeter Electrode in a half cell pH7, with [1M] redox couple were interested in Salt bridge connects the two half cells – electrons to flow, will transfer from the lowest standard electrode potential
77
what happens to the electrons in the redox couples in half cells
redox couples in solution always get spontaneous transfer of electron, depends which direction the electron is going to go depending on the affinity for a redox couple to accept an electron
78
how are standard redox potentials displayed
``` redox couples in league tables oxidised couple on LHS + at top E=0 middle Hydrogen electron - at bottom ```
79
how do redox couple interact
electrons will flow from the redox couple with the lower reduction potential to another with higher reduction potential
80
how does the reduction potential vary
depending on the percentage of the reduced and oxidised species in the solution
81
what is midpoint potential
50% of each oxidised and reduced species at pH7
82
what is the Nernst equation
describes the curve | E = Eo + (RT / nF) ln (oxidised / reduced)
83
what is E in the nernst equation
the actual potential at any point on the curve
84
what is Eo in the nernst equation
midpoint potential
85
waht is F in the nernst equation
faraday constant
86
when are 2 electrons transferred
in NADH reactions
87
what does a free energy change calculation require
concentration of redox couples
88
how is the redox potentials and free energy changes calculated
ΔG° = nF ΔEo'
89
what does n stand for in the free energy changes calculation
number of electron transferred
90
what occurs in the electron transport chain
two redox couples involved include 1/2 O2/h2O and NAD+NADH | potential difference of 1.14V between NADH and O2 drives electron through electron transport chain
91
what happens when NADH is oxidised
Free Energy is ‘released’ | but some is ‘saved’ in ATP
92
what do enthalpy values do
Enthalpy values give the amount of energy which can be released on complete oxidation of a foodstuff
93
what is E = Q - W
Internal Energy (E) is related to heat (Q) and work (W (PΔV))
94
what is ΔG° = ΔH° - TΔS°
Changes in standard Free Energy (G), Entropy (S) and Enthalpy (H) are related by the expression
95
what is ΔH = Σ (ΔH reactants) - Σ (ΔH products)
Enthalpy changes are best measured by the bomb calorimeter using the expression
96
what is ΔG° = - R.T.ln Keq
Standard Free Energy changes are measured from equilibrium studies
97
what in ΔG° = -nF ΔEo
Standard Free energy (G) changes are related to Potential Difference (ΔE) between REDOX couples

Biochemistry (13 decks)

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