Amino acids are the building blocks of proteins. They contain an amine group, a carboxylic acid group, and a side chain specific to each amino acid. Amino acids can be classified based on their side chains as aliphatic, aromatic, acidic, etc. Amino acids are also classified as essential or non-essential based on whether the human body can synthesize them. Amino acids undergo various reactions like transamination, where the amino group is transferred from one amino acid to a keto acid. They are also broken down through oxidative deamination, where the amino group is removed and converted to ammonia.

1. 08/19/13 1

2. 08/19/13 2

3. Amino Acid
08/19/13 3

4.  Amino acids are molecules containing an amine
group, a carboxylic acid group, and a side-chain that is
specific to each amino acid. The key elements of an
amino acid are carbon, hydrogen, oxygen, and
nitrogen. Amino acid is the building unit of protein ,
which have important role in our body because:

1-Amino acids used to compose antibodies which have
role in immune system against microbial infection

2-Amino acids used to regulate cell growth and bio-
synthesis of purine and pyrimidine ( this compounds
have role in DNA synthesis)
H2NCHRCOOH
08/19/13 4

5.  Amino acid classification according to reactive group or
R group
 Aliphatic - Glycine, Alanine, Valine, Leucine,
Isoleucine
 Aromatic - Phenylalanine, Tyrosine, Tryptophan
 OH- - Serine, Threonine
 Acidic - Aspartic Acid, Glutamic Acid
 Acid amide - Aspargine, Glutamine
 Basic - Arginine, Lysine, Histidine
 Sulphur - Cystine, Methionine
 Cyclic - Proline
08/19/13 5

6.  Non polar or Hydrophobic - Glycine, Alanine, Valine,
Leucine, Isoleucine, Proline
 Polar uncharged - Phenylalanine, Tryptophane, Tyrosine
 Polar charged or Hydrophillic - Serine, Threonine (OH-),
Cystine, Methionine (sulphur), Aspargine, Glutamine (acid
amide)
 Acidic or Positively charged - Aspartic Acid, Glutamic Acid
 Basic or Negatively charged - Arginine, Lysine, Histidine
08/19/13 6

7. 08/19/13 7

8.  Amino acid can be divided into the above 3 groups (non-polar,
flexible and polar) and then subdivided by their chemical
character.
 Non-Polar -- 8 Amino Acids
 Hydrocarbon Alanine, Valine, Leucine, Isoleucine, Proline
 Aromatic Phenylalanine, Tryptophane
 Thiol Ether Methionine
 Flexible -- 1 Amino Acids
 Glycine -- flexible because it has no side chain
 Polar -- 11 Amino Acids
 Alcohol Serine, Threonine, Tyrosine
 Thiol Cystine
 Amides Aspargine, Glutamine
 Acids Aspartic, Glutamic
 Bases Lysine, Arginine, Histidine
08/19/13 8

9.  From Metabolic point of view, amino acid are divided into
three groups:
 Glycogenic Amino acid
i.e : Alanine, Glycine, Methionine etc
 Ketogenic Amino acid
i.e : Lysine and Leusine
 Glucogenic and Ketogenic Amino acid
i.e : Isoleusine, Tyrosine, Phenylalanine, Tryptophan
08/19/13 9

10.  They are classified according to the side chain into:
 1- Aliphatic side chain
Alanine, Glycine, Isoleucine, Leucine, Proline and Valine.
2-Aromatic ring
Phenyl alanine, Tryptophan and Tyrosine
3-Acidic side chain
Aspartic acid and Glutamic acid
4-Amidic ( contain amide group)
Asparagine and Glutamine.
5-Sulphur containing
Cysteine and Methionine
6-Hydroxylic
Serine, Threonine and Tyrosine
7-Basic
Arginine, Histidine and Lysine
08/19/13 10

11.  They are over 300 amino acids occur in nature but 20
amino acid occur only in protein ,they classified
according to the synthesis by the body into:
Non essential amino acids
 which the body can synthesized
Alanine, Proline, Asparagine, Aspartic acid , Cysteine,
Tyrosine, Serine, Glycine, Glutamine and Glutamic acid
Essential amino acids
 which the body can’t synthesized it.
i.e: Isoleucine , leucine, Lysine, Methionine, Valine,
Phenyl alanine, Threonine,Tryptophan, Histidine and
Arginine.
08/19/13 11

12.  In chemistry, a
zwitterion is a neutral
molecule with a positive
and a negative electrical
charge (n.b. not dipoles)
at different locations
within that molecule.
Zwitterions are
sometimes also called
inner salts.
 Fig - An amino acid contain
both acidic (carboxylic acid
fragment) and basic (amine
fragment) centres. The
isomer on the right is a
zwitterion.
08/19/13 12

13.  Examples
 Amino acids are the best-known examples of
zwitterions. These compounds contain an
ammonium and a carboxylate group, and can be
viewed as arising via a kind of intramolecular acid-
base reaction:
 The amine group deprotonates the carboxylic acid.
NH2RCHCO2H NH3
+
RCHCO2
–
08/19/13 13

14.  A zwitterion is a compound with no overall
electrical charge, but which contains separate
parts which are positively and negatively
charged.
Adding an alkali to an amino acid solution
If you increase the pH of a solution of an amino
acid by adding hydroxide ions, the hydrogen ion
is removed from the -NH3
+
group. Then the
amino acid now existed as a negative ion using
electrophoresis.
08/19/13 14

15.  Adding an acid to an amino acid
solution
If you decrease the pH by adding an acid
to a solution of an amino acid, the -COO-
part of the zwitterion picks up a
hydrogen ion. This time, during
electrophoresis, the amino acid would
move towards the cathode (the negative
electrode).
08/19/13 15

16.  Phenylketonuria (PKU) is an autosomal
recessive metabolic genetic disorder
characterized by a mutation in the gene for
the hepatic enzyme phenylalanine
hydroxylase (PAH), rendering it
nonfunctional.This enzyme is necessary to
metabolize the amino acid phenylalanine
(Phe) to the amino acid tyrosine. When PAH
activity is reduced, phenylalanine
accumulates and is converted into
phenylpyruvate (also known as
phenylketone), which is detected in the
urine.
08/19/13 16

17.  If PKU is diagnosed early enough, an affected
newborn can grow up with normal brain
development, but only by managing and
controlling Phe levels through diet, or a
combination of diet and medication. Optimal
health ranges (or "target ranges") are between
120 and 360 µmol/L, and aimed to be achieved
during at least the first 10 years.When Phe
cannot be metabolized by the body, abnormally
high levels accumulate in the blood and are toxic
to the brain. When left untreated, complications
of PKU include severe mental retardation, brain
function abnormalities, microcephaly, mood
disorders, irregular motor functioning, and
behavioral problems such as attention deficit
hyperactivity disorder.
08/19/13 17

18.  The isoelectric point (pI), sometimes
abbreviated to IEP, is the pH at which a
particular molecule or surface carries no net
electrical charge.
 Amphoteric molecules called zwitterions contain
both positive and negative charges depending on
the functional groups present in the molecule.
The net charge on the molecule is affected by
pH of their surrounding environment and can
become more positively or negatively charged
due to the loss or gain of protons (H+
). The pI is
the pH value at which the molecule carries no
electrical charge or the negative and positive
charges are equal.
08/19/13 18

19.  For an amino acid with only
one amine and one carboxyl
group, the pI can be
calculated from the mean of
the pKas of this molecule. For
amino acids with more than
two ionizable groups, such as
lysine, the same formula is
used, but this time the two
pKa's used are those of the
two groups that lose and gain
a charge from the neutral
form of the amino acid.
08/19/13 19

20.  Lysine has a single
carboxylic pKa and
two amine pKa values
(one of which is on
the R-group), so fully
protonated lysine has
a +2 net charge. To
get a neutral charge,
we must deprotonate
the lysine twice, and
therefore use the R-
group and amine pKa
values (found at List
of standard amino
acids).
08/19/13 20

21.  1.General Features
 Nitrogen Balance & Metabolic Pools
 2. Degradation
 Transamination & Glutamate
Dehydrogenases
 3. Urea Cycle
 4. Sulfur-containing amino
acids
 5. Creatine & Creatinine
08/19/13 21

22.  In the human body, deamination takes place
primarily in the liver, however glutamate is also
deaminated in the kidneys. Deamination is the
process by which amino acids are broken down if
there is an excess of protein intake. The amino
group is removed from the amino acid and
converted to ammonia. The rest of the amino acid
is made up of mostly carbon and hydrogen, and is
recycled or oxidized for energy. Ammonia is toxic
to the human system, and enzymes convert it to
urea or uric acid by addition of carbon dioxide
molecules (which is not considered a deamination
process) in the urea cycle, which also takes place
in the liver. Urea and uric acid can safely diffuse
into the blood and then be excreted in urine.
08/19/13 22

23.  Guanine
Deamination of guanine results in the
formation of xanthine. Xanthine, in a
manner analogous to the enol tautomer of
guanine, selectively base pairs with
thymine instead of cytosine. This results in
a post-replicative transition mutation,
where the original G-C base pair transforms
into an A-T base pair. Correction of this
mutation involves the use of alkyladenine
glycosylase during base excision repair.
08/19/13 23

24.  Adenine
Deamination of adenine results in the
formation of hypoxanthine. Hypoxanthine,
in a manner analogous to the imine
tautomer of adenine, selectively base pairs
with cytosine instead of thymine. This
results in a post-replicative transition
mutation, where the original A-T base pair
transforms into a G-C base pair.
08/19/13 24

25.  Transamination as the name implies,
refers to the transfer of an amine group
from one molecule to another. This
reaction is catalyzed by a family of
enzymes called transaminases. Actually,
the transamination reaction results in the
exchange of an amine group on one acid
with a ketone group on another acid. It is
analogous to a double replacement
reaction.
08/19/13 25

26.  The most usual and major
keto acid involved with
transamination reactions
is alpha-ketoglutaric acid,
an intermediate in the
citric acid cycle. A
specific example is the
transamination of alanine
to make pyruvic acid and
glutamic acid. Lysine and
threonine are the only
two amino acids that do
not always undergo
transamination.
08/19/13 26

27.  Once the keto acids have been formed from the
appropriate amino acids by transamination, they
may be used for several purposes. The most
obvious is the complete metabolism into carbon
dioxide and water by the citric acid cycle.
 However, if there are excess proteins in the diet
those amino acids converted into pyruvic acid and
acetyl CoA can be converted into lipids by the
lipogenesis process. If carbohydrates are lacking in
the diet or if glucose cannot get into the cells (as
in diabetes), then those amino acids converted into
pyruvic acid and oxaloacetic acids can be
converted into glucose or glycogen.
 The hormones cortisone and cortisol from the
adrenal cortex stimulate the synthesis of glucose
from amino acids in the liver and also function as
antagonists to insulin.
08/19/13 27

28.  . Oxidative deamination is
a. the conversion of an amino acid to a keto
acid plus ammonia
b. the conversion of an amino acid to a
carboxylic acid plus ammonia
c. the transfer of an amino group from an
amino acid to a keto acid
d. the transfer of an amino group from an
amino acid to a carboxylic acid
08/19/13 28

29.  Transamination is
a. the conversion of an amino acid to a
keto acid plus ammonia
b. the conversion of an amino acid to a
carboxylic acid plus ammonia
c. the transfer of an amino group from an
amino acid to a keto acid
d. the transfer of an amino group from an
amino acid to a carboxylic acid
08/19/13 29

30. 08/19/13 30