A tea bag in a cup of hot water can be a simple model of a cell. Water moves into the tea bag and substances in the tea leaves move out through a thin layer of material. What does the thin material that holds the tea leaves represent?

It represents a  partially permeable membrane

Explanation:

As the water is added to the teabag it causes the tea leaves to move and triggers diffusion of the leaves. ... The addition of heat (from the hot water) to the tea bag causes its molecules to move much faster than at room temperature