Cell size is limited by S.A./V. ratio, since cells need large surface area to take in nutrients and excrete wastes.

Make agar "cells" with pH indicator brom cresol green (blue = basic; clear/yellow = acidic).

• PROCEDURE FOR PREPARING CELL MODELS

  Measure agar "cells": 10, 30, 50, 70 mm.

• PROCEDURE FOR FEEDING CELL MODELS p. 60

  Wear GOGGLES!

  Float agar "cells" in 0.3 N H₂SO₄ (Sulfuric Acid) for 7 minutes.

• INVESTIGATING SA/V AND FEEDING EFFICIENCY. p. 61

  Complete the tables and graph the results.