Deficiencies of brush border enzymes in the small intestine would NOT affect the complete digestion of __________.

Question

A.  fats
B.  starch
C.  DNA and RNA
D.  sucrose
E.  proteins

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you know about enzymes found on the brush border? What other information is related to the question?

Choose Answer
· Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  fats

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about enzymes found on the brush border.
· What type of thinking is required?
        o You are being asked to apply your knowledge about enzymes found on the brush border.

Gather Content
· What do you know about enzymes found on the brush border? What other information is related to the question?
        o The microvilli also participate in digestion because a number of digestive enzymes are embedded within the epithelial cells’ plasma membranes, with their active sites exposed to the chyme. These brush border enzymes include those that hydrolyze the disaccharides lactose and sucrose, and nucleases. Inactive proteases secreted by the pancreas are first activated by a brush border enzyme of the intestine.

Choose Answer
· Given what you now know, what information is most likely to produce the correct answer?
        o Starch, sucrose and nucleic acids like DNA and RNA can be digested directly by brush border enzymes. Proteins are digested indirectly, by brush border enzymes activating trypsinogen into trypsin and chymotrypsinogen into chymotrypsin which then digest the proteins. The only molecules on the list that would not be digested by brush border cell enzymes are fats, as these cells do not release lipases.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to apply your knowledge about enzymes found on the brush border. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you think that brush border cells produced lipase? Did you realize that brush border cell enzymes would activate proteases?