The calcium ion passes easily through the membrane of one cell but cannot cross the membrane of a second cell. Which part of the plasma
membrane allows this substance to cross? *
- Phosphate groups of the phospholipid bilayer allow the ions to cross.
- The fatty acid tails of the phospholipids allow the ions to cross.
- Protein channels in the plasma membrane allow the ions to cross.
- Carbohydrate groups on the membrane allow the ions to cross.