Download Amino Acids - Chemsheets

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AMINO ACIDS
H
H2N
amine
group
C
COOH
carboxylic
acid group
R
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H
H2N
C
COOH
H
glycine
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H
H2N
C
COOH
CH3
alanine
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H
H2N
C
CH
COOH
CH3
CH3
valine
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H
H2N
C
COOH
CH2OH
serine
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H
H2N
C
COOH
CH2COOH
aspartic acid
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From nobelprize.org
• amino acids are chiral (except glycine where R = H)
• only one enantiomer occurs usually
Public domain image from wikipedia
Low pH (acidic)
Neutral pH
C
H
H
H
+
H3N
High pH (alkaline)
COOH
H2N
C
R
COOH
H2N
C
_
COO
R
R
H
+
H3N
C
_
COO
R
zw itterion
© www.chemsheets.co.uk
A2 022
15-Jul-12
Draw the structure of the amino acid at the pH shown.
pH 12
pH 2
H
H2N
C
H
H2N
COOH
pH 13
H
H2N
C
COOH
H
CH3
pH 4
C
H
COOH
H2N
CH2OH
C
COOH
CH2COOH
© www.chemsheets.co.uk
A2 022
15-Jul-12
Draw the structure of the amino acid at the pH shown.
pH 12
pH 2
H
H2N
C
_
COO
H
+
H3N
C
COOH
H
CH3
pH 13
pH 4
H
+
H3N
C
H
COOH
H2N
CH2OH
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_
C
COO
_
CH2COO
A2 022
15-Jul-12
Joining amino acids together to make polypeptides and
proteins:
H
H2N
C
H
+
COOH
H2N
R
COOH
R
- H2O
H2N
C
H
O
C
C
R
Condensation reaction:
molecules join and
water is eliminated
H
N
C
H
R
COOH
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A2 022
15-Jul-12
Breaking down polypeptides and proteins into amino acids:
H2N
H
O
C
C
H
R
Needs:
acid or enzyme
N
C
H
R
Hydrolysis reaction:
reaction with water in
which O-H bond breaks
+ H2O
H
H2N
C
R
COOH
H
COOH
+
H2N
C
COOH
R
© www.chemsheets.co.uk
A2 022
15-Jul-12
Public domain image from wikipedia
Public domain image from wikipedia
Public domain image from wikipedia
Helix held in shape
by hydrogen bonds
Public domain image from wikipedia
Public domain image from wikipedia