Question

Calculate the free energy it takes at 310 K to transport a Ca2+ ion from the cytosol into the endoplasmic reticulum given the concentration in the ER is 1mM and the concentration in the cytosol is 0.1 µM when the transmembrane potential is -50 mV ( temperature 310 K). B. Could this transport occur via facilitated diffusion or does it require the input of energy from the hydrolysis of ATP (ΔG = -50 kJ/ mol) ?

Answer 1

The active transport of Ca2+

temperature is 37°C (310°K).

molecules carry a net charge of 2.

concentration gradient (1000 uM /0.1 uM = 10000)

electrostatic gradient (moving a charge against a voltage of − 50 mV).

{ R = gas constant 2 cal/mol K)

ΔG = (R)(T) x ln(10000) + (z)(F)(V_m)
= [(2)(310) x ln(200)] + [(2)(23,062)(− 0.050)
= (620) x (5.3) + 1614
= 3404.21 cal/mol
= 3.4 kcal/mole = 14225.6 J/mol

ΔG = (2)(273+37) x ln (1000 uM / 0.1 uM)
= 5710 cal/mol

ΔG = 23.848 kJ/mol