A reading activity on the Digestion of Carbohydrates

By Camilo Apita Tabinas

I would like to share this method of teaching the topic on digestion of carbohydrates. This worked with my students. You may wish to try it with your students.

Time allotted and criteria for grading the students outputs are left for the teacher to decide as students may differ from class to class.

Teaching details:

1. the teacher discusses with the students the anatomy of digestion (including the hormones involve), the roles of enzymes, and the differences between brush border enzymes and other enzymes of digestions.

2. Group the students and let them read the article below “I am Rice” (an article I composed to make the topic a little bit softer or not to appear so technical).

3. Let  each group diagram the digestion of carbohydrates based on the article they just read.

4. Let each group post their diagrams on the board side by side. Then, let the class study the diagrams posted and spot their similarities and differences.

5. Based on the comments by the students on similarities and differences of the posted diagrams, let the students decide which diagram is the closest to what the article says.

6. The teacher inserts the digestion of other carbohydrates such as disaccharide sucrose. The teacher at this point may clarify or reiterate the purpose of digestion and where it ends.

7. Finally, let each student of the class write his own revised diagram on a piece of  paper ( revisions from  the diagrams posted on the board).

Activity Proper:

Instruction for students:
 a)Read the article " I Am Rice" below; then

b) make a diagram illustrating the steps of the digestion of starch; and

c) List the enzymes involved with their specific roles in the digestion of starch.

The Article:

by  Camilo ApitaTabinas

My name is Rice. I am a good source of Carbohydrate. I am primarily a starch composed of a mixture of polysaccharides: 20% amylose(non-branched polysaccharides) and 80% amylopectin(branched polysaccharides). I can be broken down into maltose and then to glucose when digested thru enzymatic hydrolyses. Once I am in the mouth, I am mixed with saliva containing salivary amylases(enzymes): the beta amylase and alpha amylase. Here, my digestion starts. Both amylases catalyze my digestion into maltose. The alpha amylases break the glycosidic bond of my amylose chain into smaller polysaccharides and the beta amylases break the reducing parts of my amylose chain to yield maltose. As I pass down the esophagus, thru peristalsis movement, my digestion continues until I reach the stomach. In the stomach, the salivary enzymes are inactivated or destroyed by the acidic gastric juices, so my digestion temporarily stops. Some of my undigested parts(undigested starch) after around two  to four hours, continues to move down into the lumen of the small intestine where my digestion starts again. Catalyze by the enzymes pancreatic amylases, the undigested part of me(starch) is digested into maltose. Along the small intestine I, as maltose (this time), am finally digested into glucose by the brush border enzyme, maltase. Here my digestion ends and as glucose, I am absorbed thru hepatic portal vein and goes into the liver where  metabolism( at cellular level) starts. After series of biological reactions, I am now your power to do things- Energy- in the chemical form, Adenosine triphosphate (ATP).