Which Statement About Calcium Ions Is True

Multiple Choice

Which statement about calcium ions is true?

A) Calcium ions are more concentrated in the cytoplasm than outside the cell.
B) Active transport maintains the concentration differences between intracellular and extracellular levels of calcium ions.
C) A cell can increase intracellular concentrations of calcium ions by making more calcium.
D) Inositol trisphosphate (IP₃) is the only signal that causes calcium ion channels to open.
E) Calcium ions are involved in signal transduction but do not function as second messengers.