Question

A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which best describes a mechanism by which Ca²⁺ enters this cell?

a. facilitated diffusion of Ca²⁺ into the cell down its electrochemical gradient
b. movement of Ca²⁺ into the cell through an ion channel down its concentration gradient
c. passive diffusion of Ca²⁺ into the cell down its electrochemical gradient
d. cotransport of Ca²⁺ into the cell with Cl⁻
e. movement of Ca²⁺ into the cell through a carrier protein down its electrical gradient

Answer 1

b. movement of Ca²⁺ into the cell through an ion channel down its concentration gradient.

Step-by-step explanation:

Ca²⁺ ions move from the outside to the inside of the cell through an ion channel because of the difference in concentration at both sides of the cellular membrane. A Ca²⁺channel can be open or close if it is closed a change in the membrane potential opens it to let the Ca²⁺ ions inside the cell.