In the cell membrane model shown below, the molecules which move large molecules into and out of the cell are known as lipids

cholesterol

carbohydrates

proteins

Calcium and argon have the same atomic mass but have a different atomic mass because the atomic number depends upon a number of protons which is mainly different. Argon has 18 number of protons which is its atomic number and calcium has 20 number of protons. A number of neutrons and protons are different. But atomic mass (A=Z+n)  is the same. Atomic mass is the sum of the atomic number number of protons and number of neutrons.