Question

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 an uncharged molecule moves from a concentration of 10^–4 M to 10^–2 M, is the process spontaneous, at equilibrium, or does it require an input of energy?

	A.	spontaneous
	B.	at equilibrium
	C.	input of energy required
	D.	It depends on the membrane potential.
	E.	None of the answers is correct

Answer 1

1) The sarcoplasmic reticulum Ca2+ ATPase establishes a > 10,000 fold concentration gradient across the membrane.

So the right answer is

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.

2) delta G = RT ln (C2/C1) where C2 is the concentration to the side it has to be moved and C1 is the side with initial concentration

delta G = 8.314 x 298 x ln (10^-2/10^-4) = 11409 J

Since delta G is positive energy input is required

SO option C is correct "input of energy required"