Science Activity
Amino Acids and Proteins.
Model 1. Protein is present on every nutrition label, and part of many of the foods we eat. Eggs are rich in protein, so are all types of meats, even wheat flour is composed of 7-15% protein (the remaining ~70-80% is starch). The “protein” on a nutrition label represents a mixture of many different types of individual protein molecules (for a lesson on mixtures – see activity 3).
Any individual protein is a large molecule, which is sometime called a macromolecule. A protein is a macromolecule because it is comprised of smaller molecules known as amino acids joined together by covalent bonds.
C
C
O
O
H
H
H
H
e
a
c
h
l
e
t
t
e
r
r
e
p
r
e
s
e
n
t
s
a
t
y
p
e
o
f
a
t
o
m
o
r
e
l
e
m
e
n
t
s
q
u
i
g
g
l
y
l
i
n
e
m
e
a
n
s
t
h
a
t
t
h
e
m
o
l
e
c
u
l
e
h
a
s
b
e
e
n
”
c
u
t
o
f
f
”
a
t
t
h
i
s
p
o
i
n
t
f
o
r
s
i
m
p
l
i
c
i
t
y
t
h
i
s
g
r
o
u
p
o
f
a
t
o
m
s
i
s
c
a
l
l
e
d
a
n
a
m
i
n
o
g
r
o
u
p
t
h
i
s
g
r
o
u
p
o
f
a
t
o
m
s
i
s
c
a
l
l
e
d
a
c
a
r
b
o
x
y
l
i
c
a
c
i
d
T
h
e
A
n
a
t
o
m
y
o
f
a
n
A
m
i
n
o
A
c
i
d
t
h
i
s
C
i
s
c
a
l
l
e
d
t
h
e
a
l
p
h
a
c
a
r
b
o
n
Figure 5.1. The anatomy of an amino acid
e
m
o
r
i
z
a
t
i
o
n
T
a
s
k
B
e
a
b
l
e
t
o
R
E
C
O
G
N
I
Z
E
t
h
e
c
h
e
m
i
c
a
l
s
t
r
u
c
t
u
r
e
o
f
a
n
a
m
i
n
o
a
c
i
d
1. Examine figure 5.1. What type of bonds are holding the amino acid together?
2. After studying Figure 5.1, can you explain why this type of molecule is called an amino acid?
3. An amino acid could also be represented with either or both of the abbreviated structures shown below. Using the Draw tool or by inserting a shape, box the amino group amino group, star the alpha carbon and circle the carboxylic acid group.
2
N
H
C
C
O
2
H
H
2
N
H
C
C
c
a
n
b
e
f
u
t
h
e
r
a
b
b
r
e
v
i
a
t
e
d
t
o
.
.
.
O
O
H
a. What is being “abbreviated”?
b. What is wrong with the notation in the incorrect version below? Why is it wrong?
2
N
H
C
C
O
H
O
4. Amino Acids can also exist in the form shown below:
3
N
H
C
C
O
O
N
C
C
O
O
H
H
H
H
O
R
How has the amino acid changed? Does it make sense that this form of the amino acid is called a zwitterion? (Zwitter is German for hybrid)
Model 2. In living things, there are 20 amino acids that are used to make most proteins. Some of those amino acids are shown below in Figure 5.2.
C
C
C
O
O
H
H
H
H
H
H
H
N
C
C
H
O
O
H
H
H
H
N
C
C
C
O
O
H
H
H
O
H
Alanine
Glycine
Serine
N
C
C
C
O
O
H
H
H
C
H
H
H
H
H
C
N
O
H
H
Glutamine
N
C
C
C
O
O
H
H
H
S
H
Cysteine
N
C
C
O
O
H
H
H
H
C
H
H
C
O
O
H
Aspartic
Acid
H
H
H
H
H
H
Figure 5.2. Examples of amino acids.
5. Use the Draw tool or insert a shape to put a triangle around the amino group in each amino acid.
6. Use the Draw tool or insert a shape to put a circle around the carboxylic acid group in each amino acid.
7. Use the Draw tool or insert a shape to put a star next to the alpha Carbon in each amino acid
8. The remaining part of each amino acid – the rest of the molecule that is bonded to (extends down from) the alpha carbon – is called the side chain. Use the Draw tool or insert a shape to put a box around the side chain of each amino acid.
9. Using your analysis from the previous four question, what part of the chemical structure of each amino acid makes it unique from the others?
10. Below are different representations of the amino acid Valine. One or more are correct and one or more are incorrect.
C
C
C
O
O
H
H
H
C
C
H
H
H
H
H
H
H
H
H
2
N
C
C
C
O
H
O
H
3
C
C
H
3
H
H
N
H
2
C
C
C
H
O
O
H
3
C
C
H
3
H
H
2
N
C
C
C
H
H
O
O
H
3
C
C
H
3
H
H
N
C
C
C
H
O
O
H
3
C
C
H
3
H
H
N
C
C
C
O
O
H
H
C
C
H
H
H
H
H
H
H
H
H
H
H
a. Use the Draw tool or insert a shape to circle any and all correct representations of Valine.
b. Choose one incorrect representation of Valine, and use the Draw tool or insert a shape to put a box around it. Explain below why it is incorrect.
Model 3. The names of the 20 amino acids are abbreviated in two ways:
· The name is shortened to three letters: Glycine > Gly
· The name is symbolized with one letter: Glycine > G. This one letter symbol is not to be confused with the symbol of an element.
Using this information, complete table 5.1. (Abbreviations that don’t “follow the rules” have been completed for you.)
Table 5.1 The names and abbreviation for the 20 amino acids that make up proteins.
| Name | 3 letter abbrev | One letter abbrev | Name | 3 letter abbrev | One letter abbrev |
| Alanine | A | Leucine | L | ||
| Aspartic Acid | D | Lysine | K | ||
| Asparagine | Asn | N | Methionine | M | |
| Arginine | R | Phenylalanine | F | ||
| Cysteine | C | Proline | P | ||
| Glycine | Gly | G | Serine | S | |
| Glutamic Acid | E | Threonine | T | ||
| Glutamine | Gln | Q | Tryptophan | Trp | W |
| Histidine | H | Tyrosine | Y | ||
| Isoleucine | Ile | I | Valine | V |
| Figure 5.3. In proteins, amino acids are joined by peptide bonds.
|
C C C O O H H H H H H H N C C H O O H H H H N C C C O O H H O H N C C C O H C H H H H H C N O H H N C C C O H S H N C C C O H H H H H H N C C H O O H H H A l a n i n e G l y c i n e S e r i n e G l u t a m i n e C y s t e i n e t h e
n e w
c o v a l e n t
b o n d
i s
c a l l e d
a
p e p t i d e
b o n d t h e
n e w
m o l e c u l e
i s
c a l l e d
a
d i p e p t i d e
o f
a l a n i n e
a n d
g l y c i n e
r e s i d u e s N C C C O H H H H H H N C C H O H H A l a n i n e G l y c i n e A ) B ) a
g l u t a m i n e
r e s i d u e w i t h i n
a
p e n t a p e p t i d e H 2 O a
c h e m i c a l
r e a c t i o n + ( w a t e r ) t h i s
i s
a
” a n d ”
s y m b o l
n o t
a
c h a r g e .
A s
i n ,
w a t e r
A N D
a
d i p e p t i d e
a r e
p r o d u c e d H H H H H H
|
Protein structure |