Introduction

Both photosynthesis and cellular respiration are processes by which plants and animals generate and use energy. The inputs of photosynthesis are light, carbon dioxide, and water. The outputs of photosynthesis include oxygen, glucose, and ATP. In contrast, cellular respiration inputs are oxygen and glucose while the outputs of cellular respiration include carbon dioxide, water, and ATP.

Algae beads contain thousands of living algae cells. Algae is both a model organism for plants and an important element of many ecosystems. The strain of algae used in this kit, Scenedesmus obliquus, is a freshwater unicellular alga that is commonly found in clean ponds, lakes, and rivers worldwide. S. obliquus will be used in this experiment as a model organism for measuring photosynthesis and cellular respiration in plants.

In this lab, we will examine both photosynthesis and cellular respiration through the use of algae beads and a pH indicator solution. pH is a numerical indication of the acidity or basicity of a solution. pH indicators change color in response to pH changes of a solution, thus, will change colors in response to the amount of CO 2 consumed during photosynthesis or released during cellular respiration. The full range of expected colors for the CO 2 indicator solution can be seen on the Indicator Color Guide provided.

Linking Photosynthesis and Cellular Respiration

Fill in the table below with the details of photosynthesis and cellular respiration

Photosynthesis Cellular Respiration Inputs

Outputs

Part 1: Observing indicator color change

Look at the CO 2 indicator solution in the test tube, what color is it?

Using a straw, blow into the CO2 indicator solution (DO NOT drink the solution, it is not safe for consumption.) What did you notice about the color of the solution after you blew into it using the straw? *Note: you can cut off the bulb of one of the sterile pipets to use as a straw for this step.

What might explain the change in color? What are you blowing into the solution that could cause a color change?

Fill in the table below based on your current observations. Check the indicator color guide to see the full range of colors of the indicator solution.

Increase of CO 2 in solution Decrease of CO 2 in solution Observed indicator solution color change

Solution pH change (increase or decrease in pH?)

Using the observations you just made, what do you think would happen to the pH indicator if you put a plant in it?

Photosynthesis and Cellular Respiration

Objectives

1. To use algae as a model organism to investigate cellular processes

2. Examine both photosynthesis and cellular respiration through the use of a pH indicator

solution

3. Develop variable based hypothesis and prediction(s) and design and conduct an

experiment to test both.

Introduction

Both photosynthesis and cellular respiration are processes by which plants and animals

generate and use energy. The inputs of photosynthesis are light, carbon dioxide, and water. The

outputs of photosynthesis include oxygen, glucose, and ATP. In contrast, cellular respiration

inputs are oxygen and glucose while the outputs of cellular respiration include carbon dioxide,

water, and ATP.

Algae beads contain thousands of living algae cells. Algae is both a model organism for

plants and an important element of many ecosystems. The strain of algae used in this kit,

Scenedesmus obliquus, is a freshwater unicellular alga that is commonly found in clean ponds,

lakes, and rivers worldwide. S. obliquus will be used in this experiment as a model organism for

measuring photosynthesis and cellular respiration in plants.

In this lab, we will examine both photosynthesis and cellular respiration through the use of

algae beads and a pH indicator solution. pH is a numerical indication of the acidity or basicity of

a solution. pH indicators change color in response to pH changes of a solution, thus, will change

colors in response to the amount of CO2 consumed during photosynthesis or released during

cellular respiration. The full range of expected colors for the CO2 indicator solution can be seen

on the Indicator Color Guide provided.

Linking Photosynthesis and Cellular Respiration

Fill in the table below with the details of photosynthesis and cellular respiration

Photosynthesis Cellular Respiration

Inputs

Outputs

Photosynthesis and Cellular Respiration Lab

Molecules To Cells Laboratory (BIO 152)

Bradley University

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