1. Mansoura University
Faculty of Pharmacy
Biochemistry Department
AMINO ACIDS STRUCTURE & FUNCTION
PROFDR. MAMDOUH ELSHISHTAWY
BY STUDENTS IBRAHIM MAHMOUD IBRAHIM
IBRAHIM RAGAB IBRAHIM
IBRAHIM BAHGAT IBRAHIM
IBRAHIM AYMAN IBRAHIM
IBRAHIM ELDOSOKY ELNAGAR

2. Introduction

3. AMINO ACIDS PLAY CENTRAL ROLES BOTH AS BUILDING
BLOCKS OF PROTEINS AND AS INTERMEDIATES IN
METABOLISM. THE 20 AMINO ACIDS THAT ARE FOUND
WITHIN PROTEINS CONVEY A VAST ARRAY OF CHEMICAL
VERSATILITY.
THE PRECISE AMINO ACID CONTENT, AND THE SEQUENCE
OF THOSE AMINO ACIDS, OF A SPECIFIC PROTEIN, IS
DETERMINED BY THE SEQUENCE OF THE BASES IN THE GENE
THAT ENCODES THAT PROTEIN. THE CHEMICAL PROPERTIES
OF THE AMINO ACIDS OF PROTEINS DETERMINE THE
BIOLOGICAL ACTIVITY OF THE PROTEIN.

4. PROTEINS NOT ONLY CATALYZE ALL (OR MOST) OF THE
REACTIONS IN LIVING CELLS, THEY CONTROL VIRTUALLY ALL
CELLULAR PROCESS. IN ADDITION, PROTEINS CONTAIN WITHIN
THEIR AMINO ACID SEQUENCES THE NECESSARY INFORMATION
TO DETERMINE HOW THAT PROTEIN WILL FOLD INTO A THREE
DIMENSIONAL STRUCTURE, AND THE STABILITY OF THE RESULTING
STRUCTURE. THE FIELD OF PROTEIN FOLDING AND STABILITY HAS
BEEN A CRITICALLY IMPORTANT AREA OF RESEARCH FOR YEARS,
AND REMAINS TODAY ONE OF THE GREAT UNSOLVED MYSTERIES.
IT IS, HOWEVER, BEING ACTIVELY INVESTIGATED, AND PROGRESS
IS BEING MADE EVERY DAY.

5. IMPORTANCE OF AMINO ACIDS
WHEN PROTEINS ARE DIGESTED OR BROKEN DOWN, AMINO ACIDS ARE
LEFT. THE HUMAN BODY USES AMINO ACIDS TO MAKE PROTEINS TO
HELP THE BODY:
BREAK DOWN FOOD
GROW
REPAIR BODY TISSUE
PERFORM MANY OTHER BODY FUNCTIONS
AMINO ACIDS CAN ALSO BE USED AS A SOURCE OF ENERGY BY THE
BODY.

6. The Chemistry of Amino Acids

7. AMINO ACIDS ARE BIOLOGICALLY IMPORTANT ORGANIC
COMPOUNDS COMPOSED OF AMINE (-NH2)
AND CARBOXYLIC ACID (-COOH) FUNCTIONAL GROUPS,
ALONG WITH A SIDE-CHAIN SPECIFIC TO EACH
AMINO ACID. THE KEY ELEMENTS OF AN AMINO ACID
ARE CARBON,HYDROGEN, OXYGEN, AND NITROGEN,
THOUGH OTHER ELEMENTS ARE FOUND IN THE SIDE-CHAINS
OF CERTAIN AMINO ACIDS.

8. ABOUT 500 AMINO ACIDS ARE KNOWN AND CAN BE CLASSIFIED
IN MANY WAYS. THEY CAN BE CLASSIFIED ACCORDING TO THE
CORE STRUCTURAL FUNCTIONAL GROUPS' LOCATIONS AS ALPHA-
(Α-), BETA- (Β-), GAMMA- (Γ-) OR DELTA- (Δ-) AMINO ACIDS;
OTHER CATEGORIES RELATE TO POLARITY, PH LEVEL, AND SIDE-
CHAIN GROUP TYPE (ALIPHATIC, ACYCLIC,AROMATIC,
CONTAINING HYDROXYL OR SULFUR, ETC.). IN THE FORM
OF PROTEINS, AMINO ACIDS COMPRISE THE SECOND-LARGEST
COMPONENT (WATER IS THE LARGEST) OF
HUMAN MUSCLES, CELLS AND OTHER TISSUES. OUTSIDE PROTEINS,
AMINO ACIDS PERFORM CRITICAL ROLES IN PROCESSES SUCH AS
NEUROTRANSMITTER TRANSPORT AND BIOSYNTHESIS.

9. The generic
structure of an
alpha amino
acid in its un-
ionized form

10. Functions of Amino acids in Man

11. Precursors for protein synthesis :
OF more than 10.000 protein molecules
as enzymes, hormones, serum, albumin,
immuno-globulins, clotting factors, etc.

12. Act as Buffers :
Since they are amphoteric molecules ..
Because of weak positively charged
amino group & weak negatively charged
carboxylic group .

13. In Detoxification of drugs &
metabolic by-products :
e.g. Benzoic acid (toxic) + glycine →
Hippuric acid (non-toxic) water
soluble → excreted in urine .

14. In Neurotransmitters :
As Endorphins ”31 a.a” & Encephalins ”5 a.a”
Some amino acid derivatives are used as direct
neurotransmitters :
e.g. Tyrosine → Dopamine, Epinephrine, NE.
Tryptophan → Serotonin , Melatonin

15. Precursors for some biologically active
oligopeptides :
Example : oxytocin, vasopressin & GSH
And also for biological molecules like :
Histamine, NAD+ , etc ….

16. Classification of amino acids

17. They are classified according to :
Chemical
structure of
side chain
Polarity of
side chain
Biological
value
Nutritional
value

18. 1) According to chemical structure :

19. 1) According to chemical structure :
1)Amino acids with aliphatic side chains :
Alanine (Ala,A)Glycine (Gly,G)
2) Amino acids with aliphatic – branched side chains
Isoleucine (Ile,I)Leucine (Leu,L)Valine (Val,V)

20. 3) A.A with aliphatic side chains containing OH group 4) A.A with aliphatic side chains containing sulfur
Threonine (Thr,T)Serine (Ser,S) Methionine (Met,M)Cysteine (Cys,C)

21. 5) A.A with acidic side chains 6) A.A with amide side chains
Glutamic acid (Glu,E)Aspartic acid (Asp,D) Glutamine (Gln,Q)Aspargine (Asn,N)

22. 7) A.A with aromatic side chains
Tyrosine (Tyr,Y)Phenylalanine (Phe,F) Arginine (Arg,R)Lysine (Lys,K)
8) A.A with basic side chains

23. 9) A.A with heterocyclic side chains
Histidine (His,H)Proline (Pro,P)Tryptophan (Trp,W)

24. 2) According to polarity of side chain :

25. They are classified into :
A) NON-POLAR SIDE CHAINS :
THEY ARE WATER INSOLUBLE(HYDROPHOBIC) , CONTAIN NO ELECTRON RICH ATOMS (O , N, S, ..) ,
NOT GAIN OR GIVE PROTONS , NOT FORM HYDROGEN OR IONIC BONDS .
IN AQUEOUS MEDIA :
HYDROPHOBIC SIDE CHAINS CLUSTER IN THE CORE OF MOLECULE & TIGHTLY PACKED INTO THE
INSIDE , BY HYDROPHOBIC INTERACTION {VAN DER VAL FORCES} → COALESCE IN AQUEOUS
SOLUTION & CHARGED SIDE CHAINS ON THE SURFACE → LIKE MICELLE FORMATION .
B) POLAR , CHARGED SIDE CHAINS :
THEY ARE WATER SOLUBLE AND FORM IONIC BONDS & H-BONDS THEY ARE :
1) ACIDIC A.A THAT DONATE PROTONS AND FULLY IONIZED & (-) CHARGED AT NEUTRAL PH
2) BASIC A.A THAT BIND PROTONS AND FULLY IONIZED & (+) CHARGED AT NEUTRAL PH
C) POLAR , UNCHARGED SIDE CHAINS :
THEY ARE WATER SOLUBLE CONTAIN ELECTRON RICH ATOM & NOT GIVE OR ACCEPT PROTONS &
PARTICIPATE H-BOND .

26. Notes :-
It is not necessary for the two cysteine a.a
to be beside each other to form disulfide
linkage , if distant from each other →
refolding of molecule to form disulfide
linkage (3D structure) ex: Insulin .. That’s is
responsible for activity of the protein .
Reduction of disulfide bond of insulin in
acidic PH → loss of activity .
Protein contain free SH → can act as anti-
oxidant as GSH .
Disulfide bonds provide covalent links that
give the rigidity to the structure .

27. 3) According to the nutritional value :

28. They are classified into :
A) ESSENTIAL AMINO ACIDS (INDISPENSABLE) :
CAN NOT BE SYNTHESIZED IN HUMAN BODY .. SO MUST BE TAKEN IN DIET .
FAILURE TO OBTAIN ENOUGH OF EVEN 1 OF THE 10 ESSENTIAL A.A → DEGRADATION OF THE BODY
PROTEIN , A.A MUST BE IN FOOD EVERY DAY (55-56 GRAM PROTEIN RDA) .
B) SEMI-ESSENTIAL AMINO ACIDS :
CAN BE FORMED IN BODY IN SMALL QUANTITIES NOT SUFFICIENT FOR PHYSIOLOGICAL
REQUIREMENTS OF THE BODY DURING INFANCY ..SO IT MUST BE TAKEN IN DIET .
BUT , SYNTHESIZED IN ADULTHOOD (NON-ESSENTIAL) .
EX : ARGININE & HISTIDINE .
C) NON-ESSENTIAL AMINO ACIDS :
SYNTHESIZED IN THE BODY IN SUFFICIENT AMOUNTS → NOT ESSENTIAL TO BE TAKEN IN DIET .

29. 4) According to biological value :
They are classified to :
I) Pure ketogenic : that give ketone bodies only in the
body .
II) Mixed glucogenic & ketogenic : that give ketone bodies
and glucose .
III) Pure glucogenic : that give glucose only .

30. Thank you