Question

If it costs 9.9 kcal/mol to “run” the sarcoplasmic reticulum (SR) Ca ATPase (i.e., pumping one mol of Ca2+ ions from the cytoplasm to the sarcoplasmic reticulum of the muscle cell per 1 ATP hydrolyzed), then what is the minimum concentration of ATP required to provide just enough energy to run the SR Ca ATPase? In other words, what does the concentration of ATP need to be so that the free energy of ATP hydrolysis is -9.9 kcal/mol. Assume that \DeltaΔG°' is -7.3 kcal/mol, the concentration of inorganic phosphate is 3.5 mM, the concentration of ADP is 0.7 mM, the pH is 7.4, and that the temperature is 37 °C. Report your answer in terms of mM concentration to the nearest hundredth.

Answer #1

Ans> We know the ATP hydrolysis equation: ATP +
H_{2}O -------> ADP + P_{i} Also G =
G^{0} +
(RT)ln(K_{c}) where G represents the
gibbs free energy and K_{c} represents the equillibrium
constant of the ATP hydrolysis process. Now R = 1.986cal/k/mol ; T=
310K ; G^{0} =
-7.3kcal/mol ; [P_{i}] = 3.5mM ; [ADP] = 0.7mM

Now to have just sufficient amount of energy to run the CaATPase th free energy from the ATP hydrolysis process should be -9.9kcal/mol = G

Therefore substituting these values in the above equation we
get; -9900 = -7300 + (1.986 x 310)ln{[ADP][P_{i}]/[ATP]}
ln[(3.5 x 0.7)/[ATP]} = -4.223 => 2.45/[ATP] = (-4.223) =
0.01465 Therefore [ATP] = 2.45/0.01465 = 167.235mM = 1.67 x
10^{2} mM = **167 mM**

If it costs 10.5 kcal/mol to “run” a particular cation ATPase
“pump”, then what is the minimum concentration of ATP required to
provide just enough energy to run this ATPase? In other words, what
does the concentration of ATP need to be so that the free energy of
ATP hydrolysis is -10.5 kcal/mol. Report your answer to the nearest
tenth of a mM, and assume that [\Delta] ΔG°' is -7.3 kcal/mol, the
concentration of Pi is 3.4 mM, the concentration...

1.Which of the following is CORRECT concerning the sarcoplasmic
reticulum Ca2+ ATPase?
A. It is an example of an ABC transporter that interconverts
between closed and open forms.
B. It transports Ca2+ from the sarcoplasmic reticulum into the
cytoplasm.
C. This P-type ATPase maintains a calcium ion concentration of
approximately 0.1 μM in the cytosol and 1.5 mM in the sarcoplasmic
reticulum.
D. One Ca2+ is transported for each ATP hydrolyzed.
E. None of the answers is correct.
2. When...

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