Why do calcium ions Ca2 not diffuse gradient across a cell p

Why do calcium ions (Ca^2+) not diffuse gradient across a cell plasma membrane (outer cell membrane) into a cell even though the concentration is many times higher outside of the cell? (b) What is the name of the mechanism that is required for Ca^2+ to cross the plasma membrane and enter the cell?

Solution

The selective permeability of plasma membrane allows only certain molecules to pass through it freely. Large molecules and charged ions like Na⁺, Ca²⁺ . Charged ions and large molecules like glucose and proteins are transported across concentration gradient through some amount energy by active transport mechanism.

P-type ATPase transport Ca²⁺ ions across the plasma membrane.