Download Proteins

Molecules of Life
Proteins
Name:
Each team should obtain a molecular parts packet. You will use the parts to construct molecular models.
AMINO ACIDS
1.
Each team member should use a double bond to attach an oxygen atom to a carbon atom. Also, attach an –
OH group to the carbon atom. If you have studied lipids and functional groups, you should recognize this.
It is a(n) ______________________ group.
2. Now, attach three hydrogen atoms to a nitrogen atom. This is a model of the ammonia molecule. Remove
one o the hydrogen atoms. The group of atoms left (--NH2) is the _____________________ group.
Amino acids are named for the groups made in #1 and #2.
3. Attach the carboxyl and amino
groups and one hydrogen atom
to a carbon atom as shown in
Figure 1. All amino acids share this basic structure. They differ in
the atom or groups of atoms (R) which attach to the open carbon bond.
For example, attach a hydrogen atom. This is glycine (the simplest of
the amino acids).
QuickTime™ and a
decompressor
are needed to see this picture.
4. Figure 2 through 4 show some ofther grops which can attach to the carbon atom to produce other amino
acids. Construct models of at least two of these.
a. For figures 2 – 4 complete the following. Put a RED circle around the amino group. Put a GREEN
circle around the Carboxyl group. Put a BLUE circle around the central carbon. Put a BLACK circle
around the R-group.
Figure 2:
QuickTime™ and a
decompressor
are needed to see this picture.
Figure 3: Valine
b.
Alanine
QuickTime™ and a
decompressor
are needed to see t his picture.
Qui ckTime™ and a
decompressor
are needed to see thi s pi cture.
Figure 4: Glutamic Acid
How do amino acids differ from fatty acids? (BE SPECIFIC!)
5. Bring together the carboxyl end of one amino acid and the amino end of another as shown in Figure 5.
c. What molecule will you be removing to bond two amino acids together?
d. The ___________________ in the carboxyl group of amino acid 1 will bond with the
____________________ in the amino group of amino acid 2.
6. The molecule you just formed is called a PEPTIDE. The bond uniting the two molecules is a PEPTIDE BOND.
Notice that the peptide still has a carboxyl end and an amino end. This means that it can react with additional
amino acids to produce a PEPTIDE CHAIN.
7. Attach two or more amino acids to your molecule. You now have a polypeptide.
8. Proteins are formed from even longer chains that are branched, or twisted and folded. Many proteins have
amino acids which contain sulfur. Some contain iron, phosphorus, or other substances.
d. How does a polypeptide differ from a polysaccharide?