a - glucose is present in potatoes and b - glucose is present in wood. Both are glucose molecules but one can be used by humans to synthesize ATP and one cannot. Based on this information, what is the best explanation on why humans can only digest one of the glucose types?

Question

A.  a - glucose and b - glucose are stereoisomers with OH groups oriented differently.
B.  a - glucose is C6H12O6 and b - glucose is C5H12O6.
C.  Only a - glucose can form polysaccharides.
D.  a - glucose is a chain and b - glucose is a ring.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you know about the structure of carbohydrates? How does it relate to the question?

Consider Possibilities  
· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach 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.  a - glucose and b - glucose are stereoisomers with OH groups oriented differently.

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the differences in glucose found in starch and cellulose.
· What type of thinking is required?
        o You are being asked to apply your knowledge of the structures of starch and cellulose to explain the differences between these two forms of carbohydrate.
· What key words does the question contain and what do they mean?
        o a - glucose and b – glucose – both of these are chemically identical glucose molecules, but they differ in how their OH groups are oriented.
        o Synthesize ATP – this means that the glucose can be broken down and metabolized.

Gather Content
· What do you know about the structure of carbohydrates? How does it relate to the question?
        o Complex carbohydrates like glycogen, starch, cellulose and chitin are synthesized by joining glucose molecules together into long chains.

Consider Possibilities  
· What other information is related to the question? Which information is most useful?
        o Complex carbohydrates used to store energy include starch (plants) and glycogen (animals).  These contain a – glucose joined together.  These a – glucose can be broken off by enzymes and the glucose used to make ATP.
        o Structural complex carbohydrates include cellulose (plants) and chitin (animals).  These contain b – glucose joined together.  These b – glucose cannot be broken off by enzymes, which is why these carbohydrates are structural.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o a - glucose and b – glucose are chemically identical glucose molecules called stereoisomers which differ in how their OH groups are oriented.
        o a - glucose and b – glucose can both form polysaccharides when in their ring form.

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 the structure of a polysaccharide to explain some of its properties. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that both structural and energy storing forms of complex carbohydrates are made of glucose?  Did you remember that a - glucose contains bonds that can be broken by enzymes while b – glucose does not?