The Intracellular Calcium Ion Concentration of Ventricular Muscle Cells Averages

question 9

Multiple Choice

The intracellular calcium ion concentration of ventricular muscle cells averages 10-4 mmol/L during diastole. The calcium ion concentration in transverse tubules (T tubules) averages 2.5 mmol/L at rest. A protein transporter on the membrane of the T tubule exchanges sodium for calcium. The transporter uses the transmembrane sodium gradient to fuel the exchange. Which of the following transport mechanisms best describes this type of transporter?

• A)Facilitated diffusion
• B)Primary active transport
• C)Secondary active co-transport
• D)Secondary active counter-transport
• E)Simple diffusion

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