Question

21.) Consider the standard free energies shown below(T =37 °C, R-8.3 145 J/mole K) : UDP-Glucuronate + H20 UTP+ H2O M+ Pi+ PPE+ H202Pi AG =-36.9 kJ/mol 39 AG =-32.5 kJ/mol -32.5 AG-33.6 kJ/mol 1-Phosphoglucuronate+UMP+ (A) (3 pts) Calcul ate AG & Keg for the following reaction. 1-Phosphoglucuronate + UTP + H2O UDP-Glucuronate + 2Pi (B) (2 pts) Which of the following statements best describe this reaction? (A)The reaction is irreversible under standard conditions. (B) The reaction is reversible under standard conditions. (C) The reaction is at equilibrium under intracellular conditions (D) The reaction is reversible under intracellular conditions. (E) K'0 (C) (2 pts) This reaction is catalyzed by phosphoglucuronate pyrophosphorylase. How would this enzyme effect AG and Keq ? (D) (3 pts) The physiological concentration of these three metabolites in a mammalian cell at physiological temperature ( 37 °C) are: [1-Phosphoglucuronate] 0.130 mM; [UMP] = 0.140 mM, [H2O ]- 55.6 M, [H°]= 107 M and [UDP-Glucuronate] 2.33 mM [UTP] = 5.35 mM; [Pi]= 8.70 mM [PPi]= 8.14 uM What would be the actual free energy change (AG) for the reaction under these cellular conditions? UDP-Glucuronate + 2Pi 1-Phosphoglucuronate + UTP + H20

Answer 1

1101 (21) (4) The given reactions are: NDP- glucuronate +420 tphospho glucuronate tump + 2H+ AG= - 36.9 kJ .....() UTP + H₂O UMP +PP+2H+; Ao = -32.5 1 -. .-(ii) ppi tho - Pi » ago' = -33.6 KI/mol. Reversing equation () we get i-phospho ghe curonate & UMP + 2H+ UDP- glucuronate theo GDA G': +36.9 *3 won adding eanation (i), ii) & (ii) 1-phaspho grauronate & YMP taft - UDP – glucoronate ut + – upp & Pfi +24+ Pfitto - 28i +H2O 1-phorphoglucuromate glucuronate +UTP the UDP- glicovonate . This is the over all reaction + Pi . A Gover - Go' (of it) + AGol (of it) + 46o Cot iii). alloren = 36.9 t (325) + (-33.6) – 29.2 kJ/mol CAnswer) over

(21) (A) we know Gol = - Rt enker here, Go - Goverall = – 29.2 kJ/mol I ron = – 29 2009/mol R = Gas constant = 8.3145 /mol.x ta Tamperature = 37°C (273 +37)* = 310 K +29200 = 78.3145 x 310 x en Keg on enker = 29200 = 11.33 8.40 310 . 33 Ken = e""33 - 8.33 x16 (Answer) (B) the equation sgo = -f t en keq holds good when reaction is at eanilibrum & at equilibrium reactiowis reversible. At equilibrium rate of forward reaction EYAZ streverse reaction .: Answer: (6) the reaction is at equilibrium under intercellular conditions & 6 the reaction is reversible under intera cellular condition This enzyme makes Go' svet ker becomes A. So, in presence of this enzyme the reaction becomes spontaneous (1) The given reaction is: t-phospho gheeuronate at UTP+H2O (1-P) UDP lucuronale + 2P: (UDP-GM) The reaction quotient of this reaction [UDP-Gui] [Pi] 2.33x63 (8.70x103) TT-PG1 [UTP] 0430X100% x 5.35 x10 -> [: 1 mM=10-3, 20-254

mol.K wow, we know: AG = Go + RT ln & where, AG- Actual free energy change - stand and free energ change under Physiological condition R = Gar constant 2 2.3145 I mok T- Temperature = 37°C = (37 + 273)* 310K Q = 0.254 A Go' = – 29.287/mol= – 29200 I/mol » 4G = – 29200 & 8.314 5x 310 xen (0.254) – – 29200 – 3532 - – 32732 Iſmol = – 321 732 KJ/mol (Answer).