They all have different compositions of protons, neutrons, and electrons. This causes variety and makes atoms different so they can make up different substances
This is called Biomagnification - concentration of toxins in an organism as a result of its ingesting other plants or animals in which the toxins are more widely disbursed.
The four polysaccharides are glycogen, starch, cellulose, and chitlin. You consume them. They are sometimes artificially made or produced by your body.