Which amino acid is most soluble in water?

Question

A.  Valine
B.  Glycine
C.  Leucine
D.  Serine

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 solubility in water? 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

D.  Serine

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the solubility of functional groups in water.
· What type of thinking is required?
        o You are being asked to apply your knowledge of functional groups to predict which would be most soluble in water.
· What key words does the question contain and what do they mean?
        o Most soluble in water – this means that the amino acid dissolves well in water.

Gather Content
· What do you know about solubility in water? How does it relate to the question?
        o The more polar a molecule is, the better it can dissolve in water. The more non-polar functional groups a molecule has, the less soluble it will be in water.

Consider Possibilities  
· What other information is related to the question? Which information is most useful?
        o All four of the amino acids will have the same backbone structure with an amino group, an a-carbon, and a carboxyl group. The differences will be with the structure of the side chains.
        o Three of the amino acids have non-polar side chains: glycine (H), valine (C3H7), and leucine (C4H9). While none of these has polar groups, leucine has the most carbons and will be the most non-polar and hydrophobic. This will make isoleucine the least soluble in water.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Serine is the only amino acid with a polar side chain (CH2OH), the hydroxyl group (OH) will interact well with water, making serine the most soluble in water.

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 an amino acid to predict its solubility. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you know the structures of the amino acid side chains? Did you know which structures would be the most polar?