- Enzymes are proteins that catalyze chemical reactions.
- Enzymes substrates must fit to the active site.
- Catalysts speed up chemical reactions and lower the activation energy needed.
- Biology 9-12 1. b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
Prior knowledge & experience:
They know that milk has the sugar lactose in it. Lactose is made of glucose and galactose.
Some people are lactose intolerant and need to take a synthetic pill to replace the lactase enzyme they are missing.
Enzymes have a lock and key model in which substrates must fit onto the active site.
Disaccharides are carbohydrates made of two monosaccharides.
Will milk test positive for glucose?
Milk will not test positive for glucose even though its sugar lactose is a disaccharide with glucose and galactose.
Even though the lactose is a disaccharide with glucose it will not test positive for glucose.
1. Test 15 mL milk for glucose by using a glucose test strip.
2. Then put a Lactaid pill (lactase enzyme supplement) into the milk.
3. Mix the milk and pill together until the pill dissolves.
4. Test the milk again for glucose. (It now will test positive for glucose because the enzyme took the sugars apart).
Additional activities with this lab:
They also can add this enzyme to sucrose which is also a disaccharide made up of glucose and fructose. The enzyme will not however work on this disaccharide because they substrates are different. This will show them enzyme specificity.
You also can microwave the enzyme mixed with some water and then add it to milk and it will no longer work. This will show students how changing the temperature can denature enzymes.
Photographs and Movies
Sodek. Lactase Enzyme Lab. http://www.ecrhs.net/staff/dsodek/documents/lactaseenzymelab.pdf
Wartski, B. Lactase Enzyme Lab. Learn NC, a program of the University of North Carolina.