Lab 15. Lactose intolerance online lab handout2

BIO160 Fall 2021 Name: ___Evelyn Alvarado____________ Date: ___________ Class days/times____ Lab 15: Digestive system and Lactose Intolerance online Lab (adapted from HHMI Biointeractive’s “The Making of the Fittest: Got lactase? The Co-evolution of Genes and Culture) Medical professionals can determine whether a patient is lactose intolerant or not by having the patient drink a liter of milk, and then testing the patient’s blood for glucose. Why would measuring blood glucose levels tell you whether someone can digest lactose? In the intestine, the disaccharide sugar lactose in milk is broken down into glucose and galactose by the enzyme lactase (see image below). These two simpler sugars (glucose and galactose) are absorbed from the intestines into the bloodstream. As a result, if the lactase enzyme is present, blood glucose levels increase within 20 to 60 minutes of drinking milk. Most adult humans, however, do not produce lactase, which means that they are lactose intolerant. When lactose-intolerant individuals drink milk, the lactose passes undigested through the small intestine into the large intestine and may cause gas, bloating, and sometimes diarrhea. A significant minority of adults worldwide can digest milk without any problems; they are lactose tolerant. Activity 1 Watch the film “ Got Lactase? The Co-evolution of Genes and Culture .” Read each of the following statements and label them true (T) or False (F) __T___ 1. Baby mammals depend on milk to survive. ____F_ 2. Milk is a healthy food for an adult cat. __T___ 3. Throughout human history, people have always consumed the milk of other animals. __T___ 4. Lactose is a sugar in milk. __F___ 5. Most human adults around the world can digest the lactose in milk; a minority of people cannot digest lactose. __T___ 6. Digesting lactose causes a person’s blood glucose levels to increase. __F___ 7. Lactose intolerance is an allergy to milk and milk products. __T___ 8. Lactose intolerance is a genetic trait. 1

BIO160 Fall 2021 Activity 2: Watch the film “ Got Lactase? The Co-evolution of Genes and Culture . Table 1 shows the blood glucose levels of the film’s narrator, Spencer Wells, and six other individuals over time. The glucose levels were measured using glucose strips and a glucose reader similar to the one in the film. After baseline levels (i.e., the ones at “0 minutes”) were measured, each person drank a liter of milk. Their blood glucose levels were measured again at 15, 30, 45, and 60 minutes after drinking the milk. (Remember in the film Spencer’s blood glucose level rose after drinking milk since he is lactase persistent). You need to analyze the data from the rest of the individuals to figure out if they are lactose tolerant (can digest lactose to glucose) or lactose intolerant (cannot digest lactose) Table 1. Blood glucose test results for seven adults as discussed in the video Blood Glucose (mg/dL) Individual 0 minutes 15 minutes 30 minutes 45 minutes 60 minutes Spencer 117 128 146 160 152 Peter 97 111 135 154 143 Rachel 96 99 105 101 98 Katherine 95 97 99 101 102 Sarah 108 116 129 141 139 Michael 94 109 128 143 140 Arthur 97 96 94 83 88 Questions 1. What kind of molecule is lactose? a. carbohydrate b. lipid c. protein d. nucleic acid 2. In this lab, which substance was the source of lactose? Milk was the substance source of lactose. 3. What is the name of the enzyme that digests lactose into glucose and galactose? The enzyme that digests lactose into glucose and galactose is lactase . 4. What kind of molecule is an enzyme? a. carbohydrate 2

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