Download Amino Acids Worksheet - Newcastle University

1. Draw out the general structure of an amino acid.
2. What is different about this amino acid (SIMPEJ) compared
to the general structure you have just drawn? What is the
structure called? Why do you think this makes the melting
points in solid amino acids 200-300oC?
3. What conditions do you think the amino acid (TRYPTC) is in
to make its zwitterion structure to be in this form?
4. Open up the WebCSD in two separate tabs of your internet
browser and arrange them so you can see the 3D structure
on the screen at the same time. In one tab search for the
refcode LTYROS10 in the other FAZHET. Rotate the
molecule so the hydrogen atom on the central carbon is
pointing away from the screen. Draw the 2 molecules
showing their mirror images and explain why they are optical
isomers.
5. What do you notice about the two amino acids in the refcode
(ALALHC)? What type of reaction has taken place? Draw
out the molecule and highlight the new bond.
6. (Extension Question) Using the refcodes in question for can
you explain with the aid of a diagram which is L and which is
D?
Produced by Steven Carman at Newcastle University as part of a MChem project.
Answers:
1.
2. A proton has been removed from carboxylic acid and the amine has been
protonated causing each end to become charged. This is called a Zwitterion.
Due to the positive and negative ends of each zwitterion strong intermolecular
are formed which require more energy to break raising the melting point.
3. As both the amine and the carboxylic acid is protonated it suggests the amino
acid is in acidic conditions.
4.
5.
They are optical isomers as they
have a chiral centre and their mirror
images cannot be imposed on each
other.
A peptide bond has formed
between the two amino
acids via a condensation
reaction.
6.
Produced by Steven Carman at Newcastle University as part of a MChem project.