The «parts list» in these processes is similar: Microtubules, semi-rigid tubes of
protein, can serve within the cell as scaffolding, roadways, and a building
material for machinery; some
proteins serve as fasteners, binding and releasing other
materials; and motor
proteins use chemical energy to push and pull
materials along microtubules, or
move the microtubules themselves.
It includes
protein, starch, carbohydrate, vitamins, and minerals in slower
moving digestible
material that can be absorbed.