Free Radicals and Aging
Free Radicals and Aging is the idea that harmful bits inside cells slowly damage the body over time.
Think of it this way
A cut apple sits on a tray on the counter. Within minutes, the open flesh turns brown as bits in the air break it down. Over hours, more and more of the apple goes soft and dark. Free radicals do the same thing inside cells, wearing them down bit by bit.
Explaining free radicals and aging by grade level
Your body uses air to make energy, like a tiny engine. That engine makes waste bits that can harm your cells. Over time, the harm adds up and the body gets old. Fruit flies help us study this because they age fast.