Download Chemistry Worksheet Name: ___________________________ Functional Groups and Amino Acids

Chemistry Worksheet
Functional Groups and Amino Acids
Name: ___________________________
Block: ___________
.
Answer each question in the space required. Show all work.
Amino acids are the “building blocks” for proteins. Proteins are high molar mass molecules that
are created by linking amino acids end-to-end to form long chains, ranging from a few hundred to
hundreds of thousands linked amino acids. These chains of linked-amino acids fold around, crosslink, and hydrogen bond with other parts of the chain, to form the final structure of proteins. Below
are depicted only four examples of the amino acids that form proteins. (Human protein contains 20
different amino acids.)
O
H3 C
NH2
OH
NH2
Alanine (Ala)
O
O
O
O
OH
HO
NH2
Glutamine (Gln)
OH
O
NH2
Aspartic Acid (Asp)
HS
OH
NH2
Cysteine (Cys)
1. Name the functional groups that are common to these (and all) amino acids. Draw this
backbone structure using R− to label functional groups that are not in common
2. Why are amino acids called “amino acids”?
3. What is the hybridization for each of the two carbons that all amino acids have in common?
4. Examine the hydrogen atoms that are attached to the functional groups all amino acids have in
common. Which functional group is more acidic? Why?
5. The other functional group is more basic? Why?
6. For each of the amino acids listed above, name and draw the functional group that is not in
common with all amino acids. These functional groups are often called the “side groups” or
“side” chains”.
a. Ala
c. Asp
b. Gln
d. Cys
Copyright © 2014, Alan D. Crosby, Newton South High School, Newton, MA 02459
Chemistry Worksheet
Functional Groups and Amino Acids
.
Name: ___________________________
Block: ___________
7. In a certain solution pH range, amino acids form what are called “zwitterions”, from the German
meaning “hermaphrodite ions” (sometimes translated as “hybrid ions”). In short, on a single
amino acid, one of the functional groups gives up a proton to become negatively charged, and
the other functional group accepts a proton to become positively charged! Draw two Lewis
Structures for alanine: one structure should depict uncharged functional groups, while the
second structure should depict the zwitterion.
8. Look up (in a book or on the Internet) the structure for the nine essential amino acids (for
humans). Name, give the three letter designation, and draw a Lewis structure for each one.
9. Why are these nine amino acids called “essential”, when human protein is comprised of 20
amino acids?
Copyright © 2014, Alan D. Crosby, Newton South High School, Newton, MA 02459