Question

E and F only thank you

16. The concentration of TnC in muscle cells is estimated at about 70 nmol g' wet weight of tissue. 02 consumption is estimated to be about 0.09 mL O2 per m in per g wet weight of tissue. Assume the TnC is 60% saturated during normal, resting contractions. Assume that 80% of the activating Ca originates from SR stores. Assume a heart rate of 70 min. Assume free energy of ATP hydrolysis is 57 kJ mol and that metabolism derives 20.3 kJ per L of O. A. How much Cais released and taken back up per heart beat, per g of tissue? B. How much energy is consumed to take the Ca' back up into the SR, per heart beat? C. What fraction of the cell's energy consumption is used for this purpose? D. How much Ca* enters and leaves the cell across the SL membrane? E. Assuming that all of the Ca exits the SL over the NCX, how much Na enters the cell over the NCX? F. How many ATP are consumed to remove the Na' that enters over the NCX? G. What fraction of the cell's energy consumption is used for this purpose?

Answer 1

Answer:

a): 60% saturation of TnC means that the amount of Ca2+bound to TnC is 0.60 x 70 nmol g-1= 42 nmol g-1.

• This assumes a stoichiometry of Ca2+binding of 1:1 Ca2+: TnC. The free [Ca2+] makeslittle contribution to the total.
• If we assume the heart contains 70% cytosol, 1 g of tissue containsabout 0.7 mL, and an increase in free [Ca2+] of 1 :M is only 0.7 nmol g-1.

b) :

• .Since the stoichiometry of Ca2+pumping by the SERCA2a is 2 Ca2+: 1 ATP, 42 x 0.8 nmol of Ca2+requires 21 x 0.8 nmol of ATP, which is 16.8x 10-9mol g-1x 57 kJ mol-1= 0.96 x 10-6kJ g-1

c) :

• In one minute, the energy devoted to Ca2+pumping is 70 x 0.96 x 10-6kJ g-1= 67 x 10-6kJ min-1g-1The total energy consumption is 0.09 mL O2min-1g-1x 20.3 kJ L-1x 10-3L mL-1= 1.827 x 10-3kJ min-1g-1.
• The fraction of energy used by the SR is 67 x 10-6 kJ min-1g-1/ 1.827 x 10-3kJ min-1g-1= 0.037 or 3.7%

                                              Please Rate My Answer.......Thank....u.....