Lactose Enzyme Examination

Lactose is a disaccharide sugar made of galactose and glucose that is found in milk and other dairy products.  It provides one of the primary sources of nutrients for infants.  Some individuals are intolerant of lactose, meaning they are unable to digest lactose because they lack the enzyme lactase which breaks down lactose; this is common among Asian, African or people of Native American heritage and less common in people of northern or western European ancestry.  In most situations this problem can be alleviated to some degree by taking lactase enzyme tablets.  People with low lactase levels can generally consume 2-4 ounces of milk at once without causing symptoms, but larger serving sizes may cause problems[1].  

This lab will investigate some of the properties of lactose and effect of different conditions on the sugar.

Part A:  Does lactose have glucose?

Milk has the sugar lactose in it; lactose is made of glucose and galactose.  (Glucose test strips will change color depending on the amount of glucose in the sample.)  

  1. Put 15mL of milk into a 50mL beaker.
  2. Test for the presence of glucose in lactose by placing a glucose test strip in the milk for 15 seconds.  Record your test results below.

  1. Based on your glucose test on lactose, evaluate your findings using data.

  1. Place a small scoop of crushed lactaid equivalent to ¼ of a pill into the milk and allow to dissolve.

  1. Test the milk sample for the presence of glucose and record your test results below using data.

  1. Based on your glucose test on lactose, evaluate your findings.  Was anything surprising?

Part B:  Changing Conditions

Changing the environment conditions (temperature, pH, humidity, precipitation, etc.) can have an effect on organisms or the mechanisms carried out by the organism.  Select one of the options below to change the condition of the experiment to evaluate what effect of changing the experimental conditions.

Option 1: Effect of Heat

  1. Collect 15mL of hot milk in a 500ml beaker (record the milk temperature below).  

  1. Test the solution for the presence of glucose and record your results below.

  1. Add a scoop of crushed lactaid equivalent to ¼ of a lactaid pill to the hot milk and allow it to dissolve. Test the solution for the presence of glucose and record your results below.

  1. Knowing that lactose contains glucose and based on your previous observations during Part A, evaluate what effect changing the temperature had on experiment. 

Option 2: Effect of Different Sugars

  1. Collect 15mL of sucrose solution in a 500ml beaker.  

  1. Test the solution for the presence of glucose and record your results below.

  1. Add a scoop of crushed lactaid equivalent to ¼ of a lactaid pill to the sucroe solution and allow it to dissolve. Test the solution for the presence of glucose and record your results below.

  1. Knowing that sucrose contains glucose (sucrose is made of glucose and fructose) and based on your previous observations during Part A, evaluate what effect changing the type of disaccharide sugar had on the presence of glucose. 


[1] Board, A.D.A.M. Editorial. "Lactose Intolerance." Lactose Intolerance. U.S. National Library of Medicine, 18 Nov. 0000. Web. 07 Oct. 2012. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001321/>