Cell transport is movement of materials across cell membranes. Cell transport includes passive and active transport. Passive transport does not require energy whereas active transport requires energy to proceed. Passive transport proceeds through diffusion, facilitated diffusion and osmosis. The purpose of the transport proteins is to protect the cell's internal environment and to keep its balance of salts, nutrients, and proteins within a range that keeps the cell and the organism alive.
"skeletons are good age markers because teeth and bones mature at fairly predictable rates. For toddlers to teenagers up to age 21, teeth are the most accurate age indicators. Some of the best indicators of adult age are in the pelvis."
I hope this helps you ^-^
