Vernier Software & Technology

# Lactase Action

## Introduction

Lactose, a disaccharide sugar found naturally in mammalian milk, is utilized by infants as one of their initial sources of energy. During infancy, mother’s milk is often the child’s sole source of nutrition. This milk sugar, lactose, must undergo an enzymatic reaction that separates the disaccharide molecule into two monosaccharides; glucose and galactose. This action is carried out in the cells lining the small intestine. The enzyme facilitating the ‘breakage’ reaction is called lactase. After the split, the resulting simple sugar molecules are released and the lactase enzyme is available to react again. Glucose molecules are absorbed and transported to the liver while galactose molecules undergo another enzymatic reaction converting them to glucose.

In this lab, you will assess the functioning of lactase. One way is to determine if the enzyme is converting the disaccharide into glucose and galactose by measuring the amount of glucose produced. You can use glucose test strips, originally made for diabetics to detect glucose levels. The test strip turns a range of colors to indicate the sugar’s concentration in solution.

An alternative test for lactase activity measures the production of CO2 gas by yeast. Presumably, yeast are unable digest lactose directly. Yeast metabolize glucose anaerobically during fermentation, according to the equation:

${{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{l2}}}}{{\text{O}}_{\text{6}}} \to {\text{2 C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH }} + {\text{ 2 C}}{{\text{O}}_{\text{2}}} + {\text{ energy}}$

ethanol is produced and CO2 is released as the sugar breaks down in glycolysis. By monitoring pressure change caused by the production of CO2, we can use yeast to indicate lactase activity.

## Objectives

In this experiment, you will

• Test the action of lactase.
• Use glucose test paper to monitor the presence of glucose.
• Determine if yeast can metabolize glucose, lactose, or galactose.

## Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

### Option 2

You may also need an interface and software for data collection. What do I need for data collection?

## Agricultural Science with Vernier

See other experiments from the lab book.

 1 Introduction to Data Collection 2 Acids and Bases 3 Diffusion through Membranes 4 Conducting Solutions 5 Osmosis 6 Respiration of Sugars by Yeast 7 Reflection and Absorption of Light 8 Soil pH 9 Soil Salinity 10 Soil Temperature 11 Soil Moisture 12A Photosynthesis and Respiration (CO2) 12B Photosynthesis and Respiration (O2) 12C Photosynthesis and Respiration (CO2 and O2) 13 Transpiration 14A Cell Respiration (CO2) 14B Cell Respiration (O2) 14C Cell Respiration (CO2 and O2) 15 The Greenhouse Effect 16 Energy in Food 17A Enzyme Action: Testing Catalase Activity 17B Enzyme Action: Testing Catalase Activity 18A Lactase Action 18B Lactase Action 19 Oxygen Gas and Human Respiration 20 Biochemical Oxygen Demand 21 Animal Temperature 22 Lemon "Juice" 23 Ohm's Law 24 Energy Content of Fuels 25 Photovoltaic Cells 26 Wind Power 27 Watershed Testing 28 Interdependence of Plants and Animals 29 Biodiversity and Ecosystems

### Experiment 18B from Agricultural Science with Vernier Lab Book

#### Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.