Module 4 - Activity 3

Activity 1 : : Activity 2 : : Activity 3 : : Activity 4 : : Activity 5

Activity 3: Interactive Learning Resources

Missing Molecule

Go to: http://highered.mcgraw-hill.com/sites/0072907932/student_view0/chapter_18/case_study_two.html and review the case study on lactose intolerance.

Lactase is one of the many enzymes required for complete digestion of the disaccharide lactose.

• How common is lactose intolerance?
• Is lactose intolerance an allergy?

Digestion is a series of cascading events requiring many enzymes, hormones, muscular movement, water, energy, and buffers. Lactose intolerance is only one example of when one single step is missing in the process of digestion.

Introduction to Digestion

Explore the virtual digestion website at: www.acm.uiuc.edu/sigbio/project/digestive/index.html

• What part of the GI tract does the majority of mechanical digestion occur? Chemical digestion?
• What organs provide enzymes and where do the enzymes enter the GI tract?
• What is the function of each enzyme?
• What hormones are involved in digestion and what are their roles?
• What other secretions are necessary for digestion?

Add the organs involved in digestion along with their functions and secretions to your concept map.

Barriers to Digestion

Lactose Intolerance:

Review the Lactose Intolerance page from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/
• What populations have a high incidence of lactose intolerance?
• What other nutrients are of concern when dairy products are omitted from the diet?
• Can someone have a healthy diet without diary products?

Constipation and Diarrhea:

Review the Constipation and Diarrhea sections on the NIDDK site:
• http://digestive.niddk.nih.gov/ddiseases/pubs/constipation/
• http://digestive.niddk.nih.gov/ddiseases/pubs/diarrhea/

Heartburn, Gastroesophageal Reflux (GER), and Gastroesophageal Reflux Disease (GERD):

Review the section on heartburn, GER, and GERD on the NIDDK site:
• http://digestive.niddk.nih.gov/ddiseases/pubs/gerd/index.htm

Nutrient Absorption and Transport

Absorption can occur by:
• Simple diffusion
• Facilitated diffusion
• Active transport or
• Pinocytosis

Review the diagram of the intestinal wall and methods of absorption at: www.mc.maricopa.edu/~lauramay/Digestion/absorption.htm

Water soluble molecules are absorbed directly into portal circulation. Fat soluble molecules are absorbed and transported through the lymphatic system. Eventually they are mixed with general circulation near the heart.

Update your concept map to include end products of digestion along with which mode of absorption and transport it will take.