### Introduction

Yeast can metabolize sugar in two ways, aerobically, with the aid of oxygen, or anaerobically, without oxygen. When yeast metabolizes a sugar under anaerobic conditions, ethanol (CH3CH2OH) and carbon dioxide (CO2) gas are produced. An equation for the fermentation of the simple sugar glucose (C6H12O6) is:

The metabolic activity of yeast can be determined by the measurement of gas pressure inside the fermentation vessel.

### Objectives

In the Preliminary Activity, you will use a spectrophotometer to measure color changes in DPIP due to photosynthesis by chloroplasts.

After completing the Preliminary Activity, you will first use reference sources to find out more about photosynthesis by chloroplasts before you choose and investigate a researchable question dealing with photosynthesis. Some topics to consider in your reference search are:

• photosynthesis
• chlorophyll
• chloroplast
• ATP