Glycolysis
Glycolysis is the first step cells use to break sugar apart and release energy.
Think of it this way
A whole grape sits in the center of a cutting board. A knife splits it into two equal halves and lays them flat. Each half releases a small drop of juice into a bowl below. That juice is the energy the cell can now use.
Explaining glycolysis by grade level
When yeast eats grape sugar, it does not swallow it whole. It snaps the sugar into smaller bits first. That snapping gives the yeast a burst of power. Every living cell does this same thing to get energy from food.