is a compound that absorbs light 3 What reagent is used to look for starch after the leaves are decolorized 4 What is used to block sunlight from the Geranium leaf 2 A OBJECTIVES Understand the process of photosynthesis Describe its phases reactants and products Explain how to measure photosynthesis rate in Elodea Hornwort plant Understand the role of different pigments in photosynthesis Correlate the chemical structure of pigments with its mobility on the chromatography paper INTRODUCTION Photosynthesis is the process of converting light energy to chemical energy This process i essential to life on earth Photosynthesis is a reaction between carbon dioxide water and ligh to produce glucose The reaction is as follows 6CO2 6H2O Light energy C6H12O6 602 Photosynthesis occurs in two stages During the first stage of photosynthesis light energy is captured by the chloroplasts and converted into chemical energy This chemical energy is used in the second stage of photosynthesis called the carbon fixation stage In this stage the chemica energy produced from the first stage powers the conversion of CO to glucose This stage car occur whether light is present or not and is called the light independent stage Even though carbon fixation can occur without light light is still needed for the first stage of photosynthesis to provide the chemical energy needed for the second stage Thus carbon dioxide cannot be utilized to produce glucose if energy from sunlight is not captured and converted to chemica energy at some point during the process of photosynthesis Once glucose is made it can be converted to other sugars e g sucrose and transported in the plant or glucose can be stored in the plant as starch a polymer of glucose In the following laboratory exercises You wil