Amino acids and proteins. model 1. protein is present on ev

1. 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.
N
C
C
O
O
H
H
H
H
e
a
c
h
l
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t

2. e
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3. e
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q
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m
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a
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4. c
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n
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c
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f
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5. t
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6. i
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c
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d
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7. f
a
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m
s
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c
a
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d
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b
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T

8. h
e
A
n
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f
a
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A
m
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o
A
c
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d
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i
s
C
i
s

9. c
a
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d
t
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nFigure 5.1. The anatomy of an amino acid
M
e
m
o
r
i
z
a

10. t
i
o
n
T
a
s
k
B
e
a
b
l
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t
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R
E
C
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G
N
I
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E
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c

11. h
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m
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c
a
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d
1. Examine figure 5.1. What type of bonds

12. are holding the amino acid together?
2. After studying Figure 5.1, can you explain why this type of
molecule is called an aminoacid?
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.
H
2
N
H
C
C
O
2
H
H
2
N
H
C
C
c
a
n
b
e
f
u
t
h
e

13. 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?
H
2
N
H
C
C
O

14. H
O
4. Amino Acids can also exist in the form shown below:
H
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.
N

15. 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

16. 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

17. 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

18. 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.
N
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

19. 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

20. 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

21. 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

22. 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

23. 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.
N
C
C
C
O
O
H
H
H

24. 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

25. 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

26. n
i
n
e
G
l
y
c
i
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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

27. e
n
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w
c
o
v
a
l
e
n
t
b
o
n
d
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s
c
a
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d
a
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p
t

28. i
d
e
b
o
n
d
t
h
e
n
e
w
m
o
l
e
c
u
l
e
i
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c
a
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d
a

29. d
i
p
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p
t
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e
o
f
a
l
a
n
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e
a
n
d
g
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r
e

30. 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

31. n
e
A
)
B
)
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a
m
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s
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w
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t
h
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n
a
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e

32. n
t
a
p
e
p
t
i
d
e
H
2
O
a
c
h
e
m
i
c
a
l
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e
a
c
t
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n
+
(
w
a

33. t
e
r
)
t
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a
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a
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d
"
s
y
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t
a
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h
a

34. r
g
e
.
A
s
i
n
,
w
a
t
e
r
A
N
D
a
d
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p
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p
t
i
d
e
a
r

35. e
p
r
o
d
u
c
e
d
H
H
H
H
H
H
Protein structure
Model 4: To be a protein, the amino acids must be joined
together in a chemical reaction. In a protein, amino acids are
joined by a particular type of covalent bond called a peptide
bond.
The order of amino acids that are joined by peptide bonds into a
protein is very significant. This order of amino acids is read
starting from the free amino group and ending at the free
carboxylic acid group. This order is called a primary sequence
of amino acids. Amino acids within a protein are called amino
acid residues. Proteins are composed of as few as 100 and as
many as 1000 amino acids joined by peptide bonds. This means
that in any given protein, each of the 20 amino acids is usually
present multiple times.

36. NCC
CH
3
OH
H
H
NCC
H
OHH
NCC
OHH
NCC
C
OHH
NCC
C
OH
OHH
C
C
C
N
O
HH
HH
H
H
SO
Free amino
group
Free carboxylic
acid group
AlanineGlycine
GlutamineCysteine

37. Serine
The sequence of this peptide reads
AGQCS
HH
H
HH
H
Figure 5.4. Peptide sequence
There are many, many, many proteins in the natural world, and
each one is different from the next because of their primary
sequence. Each unique protein is comprised of amino acids but
with a unique sequence/order.
.
.
.
E
L
V
I
S
L
I
V
E
S
.
.
.
.
.
.
K

38. I
T
C
H
E
N
S
C
I
E
N
C
E
.
.
.
.
.
.
I
L
I
K
E
C
H
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M
I
S
T
R
Y
.
.
.

39. a
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f
p
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40. e
t
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c
a
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p
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E
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41. r
e
s
e
n
t
s
a
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d
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u
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o
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.
I
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l
t
h
r
e

42. e
p
r
o
t
e
i
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s
w
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r
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p
r
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s
e
n
t
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t
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s
a
m
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m
i
x
t
u
r
e

43. ,
t
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m
i
x
t
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w
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a
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i

44. n
"
.
Glutenin and gliadin are the two proteins from wheat flour that
are responsible for making the proteinacious matrix called
“gluten” found in bread.
Glutenin is a large protein of >1000 amino acids. A short 30
amino acid portion of the glutenin primary sequence is shown
below:
…PGQLQQPAQGQQGQQPGQAQQGQQPGQGQQ…
(the dots… mean the protein keeps going)
Here is a short 30 amino acid portion of the gliadin primary
sequence:
…QLQPFPQPQLPYPQPQLPYPQPQLYPPQPQ…
11. In Figure 5.3A, to make a peptide bond, between alanine
and glycine, a chemical reaction was necessary. Describe what
the chemical reaction required. What happened in order to make
the new peptide bond? When chemists speak of chemical
reactions, they talk of bonds broken and bonds formed. Use
those phrases in your explanation.
12. In part B of Figure 5.3, use the Draw tool or insert a shape
to put an arrow pointing to each peptide bond of the
pentapeptide shown (a peptide of 5 amino acids)
13. If you had started with all free amino acids, how many
water molecules would you have formed in making the
pentapeptide in the previous question?
14. What amino acids are represented by the one letter symbols
in glutenin? List them: Which amino acid is present in greater
number than all the others in glutenin? In gliadin?
� For a lesson on bonding, see Activity 2

45. PAGE
Copyright © 2016 Wiley, Inc.
Page 9
_1388581537.cdx
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_1519925398.cdx
_1464515278.cdx
_1388838318.cdx
_1388565979.cdx
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_1373967692.unknown