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Flashcards

bioenergetics

Lydia McCarrick biochemistry univeristy English 46 cards

Cards in this deck (46)

  1. 1Key characteristics of living matter:1) structurally complicated/highly organised
    2) extracts transforms and uses energy form environment
    3) capacity for self replication/assembly
  2. 2What is the definition of energy and bioenergetics?1) capacity to do work
    2) describes how living systems, capture, transform and use energy to perform work and stay alive.
  3. 35 examples of biological work1) synthetic
    2) concentration
    3) mechanical
    4) electrical
    5) bioluminescent
  4. 4What is energy for bioscientists? What do they use to measure energy?The chemical energy energy exchanged in a reaction, use equilibrium thermodynamics.
  5. 5What is the definition of equilibrium thermodynamics?systematic study of transformation of energy that occurs in a closed system as it reaches equilibrium
  6. 6what is the definition of a: 1) system 2) open system 3) closed system 4) isolated system1) matter within defined region of space
    2) matter/energy exchange between the system and the surroundings
    3) matter within system and energy exchange between system and surroundings
    4) no exchange between system and surroundings
  7. 7What is the first law of thermodynamics?energy within a system is conserved, it can be changed from one form to another but it can't be created or destroyed
  8. 8What is the equation for the first law of thermodynamics?E= Q-W
    internal energy= heat - work
  9. 9What are the principles of bomb calorimetry?Measures energy produced by combustion/ oxidation of a substrate and this can be measured as change in internal energy i.e. delta E
    1) if reaction occurs in insulated container then NO HEAT EXCHANGE E=W
    2) if no change in volume then delta E=Q
  10. 10Define enthalpy what is the equation that links inernal energy, pressure, volume and enthalpy?measure of heat change during a reaction at constant pressure and volume
    Delta E= delta H (J) - (P deltaV)
    change in internal energy is equal to change in enthalpy minus pressure x volume
    (more useful for living systems as pressure and volume doesn't change in living systems)
  11. 11how many joules in a calorie ? what is the enthalpy value for exothermic reactions?4.18 J
    always negative
  12. 12What are the conditions that enthalpy values are measured under?under standard conditions i.e. molar quantities, atmospheric pressure and 25 degrees c or 298 K (must use kelvin for these reactions)
    - for kelvin add 273 to degrees c
  13. 13how does lactobacillus live and how can we calculate it's energy efficiency?1) lives by converting glucose to lactate
    2) efficiency= energy in/energy out x 100
  14. 14What energy/respiration does 1) sprinters use 2) marathon runners use 2) heart muscle use? 4) skeletal muscle1) fast muscle, glucose to lactate
    (anaerobic and inefficient)
    2) slow muscle, glucose/fat to co2/h2o
    ( aerobic and efficient)
    3) FA- co2 and h20
    (aerboic and efficient)
    4) same as lactobacillus
  15. 15what does enthalpy changes involve? what is useful and useless energy?1) changes in useful and useless energy
    2) USEFUL= G i.e. free energy
    USELESS: S i.e. entropy
  16. 16What is the gibbs helmholtz equation?delta G = delta H - (t x delta s)
    gibbs/ free energy = enthalpy - ( absolute temp (kelvin) x entropy)
  17. 17What is the second law of thermodynamics?For a reaction to occur the free energy must decrease and entropy must increase.
  18. 18What does change in free energy mean in a equilibrium reaction?1) if G > 0 then product/forward reaction favoured
    2) is G<0 then backward reaction favoured
    3) G= 0 then it's equilibrium
    -generally within metabolic pathways reactions are irreversible
  19. 19What is entropy?-measure of disorder within a system
    - relates to a change from a less probable to a more probable state i.e. increase in disorder in a reaction increases the possibility of a reaction taking place
  20. 20What is the boltzmann equation?S= K. ln (rate of forward/ rate of backward)
    entropy= boltzmann constant x natural log of ( forward of backward reaction)
    - shows statistical distribution of matter/ molecules within a given system
    - also shows which way round a reaction is occurring at equilibrium
  21. 21what is the boltzmann constant ?1.381 x 10-23 Joules/mol/degree kelvin
  22. 22What is the equation for the K of equilibrium?K= [products]/ [reactants]
  23. 23what is the equation for the standard free energy change from equilibrium studies?G= -R.T ln Keq
    =-gas constant x absolute temp x ln (Keq)
    = - 8.31 x ( 273 + degress) x ln ( mol dm(-3))
  24. 24Actual free energy change for any set of conditions in biochemistry? (because they occur at low conc)change in G= G change under standard condition + (RT x ln [products]/[reactants])
  25. 25What is most of a cell's free energy used for?synthesise proteins by creating peptide bonds
  26. 26Energetics of peptide bonds and protein synthesis?-reactions driven by hydrolysis of ATP/GTP delta G = -31KJ
    - the 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
    -i.e. large negative free energy change and therefore overall delta g= negative and second law is upheld
    - this process called energy coupling
    - in theory 3 X ATP/GTP for every bond produced
  27. 27what is energy used for within cell?1) creating cellular structure
    2) active transport of nutrients
    3) synthesis of AA
    4) wasteful/ futile cycle of protein turnover
  28. 28Why use ATP a energy molecule?-HIGH ENERGY PHOSPHATE BONDS: bonds whose hydrolysis produce a larger than expected decrease in free energy
    (30KJ of energy stored in bonds)
  29. 29What is the origin of the high energy phosphate bonds? What is the energy charge of the cell?1) relief of charge/ charge repulsion between phosphates
    2) increased possibilities for resonance and deolocalisation
    -the ratio of ATP/AMP within the cell
  30. 30How is ATP hydrolysed?two step reaction
    1) hydrolysis of end phosphate molecule/ bond releases group and adds hyrodxyl group onto both phosphates ( irreversible reaction) makes ADP( 2-)
    2) reversible ionisation reaction removes H+ from end of ADP(2-) which makes aDP 3- and donates H+ to solo phosphate group
  31. 31How is ATP re-charged and how does the process uphold the second law of thermodynamics?1) continually recharged by coupling reactions ( pyruvate production)
    2) phosphoenol pyruvate + ATP + Pi---------> ATP + Pyruvate and H20
    enzyme: pyruvate kinase
    3) two step reaction
    ADP + Pi= ATP + 30 kj
    h20 + PEP= pyruvate = -52 KJ
    overall G= -22 kJ so second law upheld
  32. 32Overall energetics of glucose metabolism2 step reaction i.e. energy coupling
    1) glucose and 602 -----> 6co2 and 6 H20 (-2780 KJ)
    2) 38 ADP and 38Pi= 38 ATP and 38 H20 ( 1140 i.e. 38 x 30)
    OVERALL: -1730 kJ
    out of 2780 kJ of energy produced 1730 are stored in ATP
  33. 33REDOX COUPLES-always put oxidised couple on the left
    1) Nad+/NADH
    2) Pyruvic/lactic
    3) 1/2 02/ H20
    - it is difficult to transfer electrons in covalent compounds so often whole atoms are transferred instead
  34. 34What is the definition of standard redox/reduction potential ?is the measure of affinity for a redox couple to accept an electron (reading on the voltmeter as soon as salt bridge is connected)
  35. 35How is standard reduction potential measured?REFERENCE CELL:
    -known emf
    -H2 gas pumped at 101.3 kpi and equilibrated with 1 MH+
    TEST CELL:
    - containing 1 M conc of oxidised + reduced species of the redox pair to be examined at PH 7
  36. 36how to work out whether a species will be oxidised or reduced from standard reduction potentials?-redox couples are in league tables
    1) more negative the potential the lower the affinity for electrons so more likely to be oxidised
    2) higher potential has greater electron affinity so will be reduced
    - this means tables show electron flow
    - reference cell i.e. hydrogen cell has potential of zero
  37. 37How to use cell to show flow of electrons? What does direction of electron flow depend on ?- set up two half cells each with redox couple within
    e.g pyr/lac half cell + NAD+/NADH 1/2 cell
    -depends on potential difference between the couples
    - one cell will be oxidised and one will be reduced
  38. 38The NERNST equation: what does it show?-although a redox couple can have a tendency to iodise or reduce this can change depending on the other species/redox pair
    - curve shows how tendency to release e- changes
  39. 39What is the NERNST equation?E= E0 + ((RT/nF)) ln (%oxidised/%reduced)
    E= actual midpoint at any point on the curve
    E0= midpoint potential
    T= absolute temp
    N= No. of e- transferred
    F= faraday constant (96500 J/V mol) ln= natural log
    r= gas constant 8.31
  40. 40What is the midpoint potential?midpoint potential measured at pH7 ( 50% of species is oxidised and 50% is reduced)
  41. 41What is the potential difference between the couples related to?P.D or delta E is related to the equilibrium constant and change in free energy
    - delta G= -nF x delta E
    - as a result it is possible to calculate free energy changes from any biological oxidation reaction at any concentration of redox couples
  42. 42How to work out potential difference between redox couples when given standard reduction potential values?most positive value - most negative value
    e.g. value of 1.14 V between NADH and 02 drives e- through E.T.C.
  43. 43Why isn't all energy produced by E.T.C used to form ATP/process is only 41% efficient, this in theory provides efficient energy in NADH to rephosphorylate 7 ADP but E.T.C. would then become almost completely REVERSIBLE therefore energy has to be wasted to get a reaction to go in one direction, the more you waste the more reversible the reaction becomes.
  44. 44Where is non-equilbirum thermodynamic applicable?In living organisms as they are open systems i.e. matter and energy flow through therefor equilibrium thermodynamics don't apply
    -NET: as long as overall increase in entropy there can be a local decrease
  45. 45Give examples of 1) source 2) open system 3)sink1) nutrients, food, sun
    2) living cell, animal, biosphere
    3) co2,H20, Nh4+, excretion/radiation into space
  46. 46What is oscillating Zhabotinski reaction based on?-based on oxidation/ reduction of cerium ions
    - reaction never reaches equilibrium shown by constant colour change
    MIXTURE: potassium bromate, cerium sulphate, citric acid all in dilute sulphuric acid with redox indicator

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univeristy biochemistry Flashcards on bioenergetics , created by Lydia McCarrick on 16/05/2015.
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Lydia McCarrick
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