Lactose Intolerance
Cécile Bardel, Charles Baudelaire
Target Group
16-17 years old students
Brief Description
Lactose Intolerance



Topic Handout (1/2)

Overview and research to carry out

Mr. X consults a doctor following his young son experiencing digestive problems (bloating, diarrhoea, stomach cramps) which appear to  systematically occur after the consumption of dairy products. The doctor suspects an intolerance to lactose, which corresponds to an inability to digest the lactose present in dairy. 

The aim is to verify is Mr. X’s child is indeed lactose intolerant.  


In the jejunum (part of the small intestine), lactase catalyses the transformation of the lactose into

galactose and glucose, two simple sugars capable of being digested as they can cross the partially permeable membrane of the two intestines’ cells.bfNIv8ZKsMR8BFiD4yMQJDw5TQSprAi+5y8elk0q


A lactose intolerance is an illness which is a result of the absence of lactase production by the cells in thejejunum. In absence of this enzyme, lactose

is transformed by the bacteria of the intestinal flora, which is behind the symptoms of the illness.  

Diagram of the structure of the intestines in a human

Step 1: Plan an experiment to help to resolve the problem (10 minutes maximum)

Come up with a feasible experiment which would allow you to check if Mr. X’s child is indeed lactose intolerant.


Topic Handout (2/2)

Step 2: Carry out the experiment to obtain exploitable data

Carry out the test-tube experiment on digestion of lactose in order to verify if Mr. X’s child is indeed lactose intolerant.                                                                                                                           

Step 3: Process the data and present your findings

In the form of your choice, process and present the raw data so that you have the necessary information to respond to the problem. 

Step 4: Used the obtained results to respond to the problem and answer the question

Process the results to verify if Mr. X’s child is indeed lactose intolerant


Experiment Protocol Handout

Equipment available and protocol for using the equipment


-          Water bath kept at 37°C

-          Thermometer

-          Stopwatch

-          Test tubes

-          Pipettes (3x1 ml, 1x 5ml)

-          2 pipette bulb

-          Titration plate

-          Glucose test strips

-          Lactose solution

-          Intestinal fluid taken from the patient’s jejunum patient = solution A

-          Intestinal fluid taken from a healthy individual’s jejunum = solution B

-          Distilled Water

-          Hydrochloric acid

-          Marker

To Test if Mr. X’s child is intolerant to Lactose

-          Carry out three tests for the hydrolysis of lactose, observing the conditions indicated in the table below. 

-          Use glucose test strips to detect any glucose before putting them in the test tubes and after the reaction has taken place.

Solution of intestinal fluids
Distilled water
Hydrochloric Acid
Reaction time
Volume (ml)
Volume (mL)



in the

water bath

37 °C

3A101 drop
3B101 drop
3--11 drop

Health and Safety: among the products used,g+LgDcAAAAAElFTkSuQmCC

we have hydrochloric acid which is a corrosive chemical. 

Handling Precautions

Follow the usage instructions for the glucose test strips by referring to the instructions provided on the bottle.



Lab sheet for the teacher

Equipment for the student:

-          Water bath kept at 37°C (use a thermometer if necessary)

-          Stopwatch

-          3 test tubes 

-          3 1ml pipettes + 1 5ml pipette + 2 pipette bulbs or equivalent

-          6 glucose test strips in their original box (for instructions on usage and reading the results)

-          A titration plate allowing a simple use for the glucose strip tests.

-          Lactose solution at 10g/l

-          Intestinal fluid from the patient’s jejunum = solution A = solution with or without lactase (to vary the results)

-          Intestinal fluid taken from a healthy person’s jejunum = solution B = solution with lactase (two tablets for 500ml of water)

-          Distilled Water

-          Hydrochloric acid  0.1M (with a pipette if the bottle doesn’t already have one)

-          1 marker  


Expected result




Related files

expected result for the experiment 166 KB
Lactose Intolerance 420 KB
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