Amino Acids (1) IUA, 2012

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Amino Acids (1) Atif H. Khirelsied, Ph.D. Atif H. Khirelsied, Ph.D. Department of Biochemistry Faculty of Medicine International University of Africa, Khartoum, Sudan

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Amino Acids (1)Atif H. Khirelsied, Ph.D.   Atif H. Khirelsied, Ph.D.Department of BiochemistryFaculty of MedicineInternational University of Africa, Khartoum, SudanAmino Acids1. Amino acids (aa) are organic acids with an amine Amino acids (aa) are organic acids with an amine group.  2. They are the "building blocks" of proteins. 3. Have a wide range of diverse biological functions. 4. There are more than 300 in nature. 4 There are more than 300 aa in nature 5. Only 20 L‐α‐amino acids ar

Transcript of Amino Acids (1) IUA, 2012

Page 1: Amino Acids (1) IUA, 2012

Amino Acids (1)

Atif H. Khirelsied, Ph.D.Atif H. Khirelsied, Ph.D.  

Department of BiochemistryFaculty of Medicine

International University of Africa, Khartoum, Sudan

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Amino Acids

1. Amino acids (aa) are organic acids with an amine1. Amino acids (aa) are organic acids with an aminegroup. 

2. They are the "building blocks" of proteins.

3. Have a wide range of diverse biological functions.

4 There are more than 300 aa in nature4. There are more than 300 aa in nature.

5. Only 20 L‐α‐amino acids are found in proteins.Atif Hassan Khirelsied

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Amino Acids

5. D‐Amino acids occur in bacteria and peptide ibi iantibiotics.

6 S l h i id f d i i6. Several other amino acids are found in non‐protein substances. 

Atif Hassan Khirelsied

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Amino Acids Structure

A typical amino acid has a primary amino group, a carboxyl group, a hydrogen atom and a side‐chain (R group) attached to a chiral α carbon atomchiral α carbon atom.

Atif Hassan Khirelsied

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Amino Acids Structure

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The Functions of Amino Acids

• They are the "building blocks" of proteins.y g p

• Are important (essential) nutrients• Are important (essential) nutrients.

• Components of various biomolecules e.g., serine in phospholipids.

Atif Hassan Khirelsied

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The Functions of Amino Acids

• Precursor for various biologic substances• Precursor for various biologic substances.

– Glucose.

– Heme.

– Purines and pyrimidines.

– Neurotransmitters.

– Hormones– Hormones

Atif Hassan Khirelsied

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Amino acids, isomerism & optical activity


All standard α‐amino acids except glycine and proline have chiral

carbons (the αC), thus exist in pairs of (D) and (L) enantiomers.

Atif Hassan Khirelsied

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Amino acids classifications

• Amino acids can be classified according to:

1 Chemical nature of R groups1. Chemical nature of R‐groups

2. Solubility

3.  Dietary importance

4. Metabolic fate

Atif Hassan Khirelsied

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Amino acids; classification by R-group

• According to the chemical nature of the side chain,According to the chemical nature of the side chain, amino acids can be classified into:1 Aliphatic non‐polar amino acids1. Aliphatic non‐polar amino acids.

2. Sulfur containing amino acids.

3 H d l t i i i id3. Hydroxyl containing amino acids.

4. Aromatic amino acids.

5. Acidic amino acids and their amides.

6. Basic amino acids.

7. Imino acid

Atif Hassan Khirelsied

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The aliphatic non‐polar amino acids

This class include:

1 Glycine1. Glycine

2. Alanine

3. Valine

4. Leucine 4. Leucine

5. Isoleucine

Atif Hassan Khirelsied

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The aliphatic non‐polar amino acids

1 Glycine 1. Glycine

(Gly or G).


•Is the smallest amino acid.

•Has the simplest structure.p

•Does not exist as a pair of stereoisomers

Atif Hassan Khirelsied

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The aliphatic non‐polar amino acids

2 Alanine2. Alanine

(Ala or A)( )


•Is aliphatic amino acid.

•Has a methyl group in the side-chain position.


Atif Hassan Khirelsied

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The aliphatic non‐polar amino acids

3. Valine, Val , (V).

4 Leucine 4. Leucine, Leu, (L).

5. Isoleucine, Ile, (I).

Atif Hassan Khirelsied

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The aliphatic non‐polar amino acids

6.Methionine, Met, (M).


The aliphatic side‐chains of Ala, Val, Leu, Ile  & Met are 

non‐reactive, hydrophobic.

Atif Hassan Khirelsied

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The sulphur containing amino acids

7. CysteineCys, (C).

MethionineMet (M)Met (M)

Note Met is also an aliphatic non-polar amino acid

Atif Hassan Khirelsied

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The hydroxyl containing amino acids

8. SerineSer, (S).

9. ThreonineThr, (T).

T iTyrosineTyr, (Y).

Atif Hassan Khirelsied

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The acidic amino acids and their amides

10. Aspartic acidAsp,(D)

11. AsparagineAsn, (N).

Atif Hassan Khirelsied

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The acidic amino acids and their amides

12.Glutamic acidGlu, (E).Glu, (E).

13 Gl t i13. GlutamineGln, (Q).

Atif Hassan Khirelsied

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The basic amino acids

14 Araginine14. AraginineArg, (R).

15. LysineLys, (K).Lys, (K).

16.HistidineHis (H)

Atif Hassan Khirelsied

His, (H).

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The aromatic amino acids

17. PhenylalaninePhe, (F).

18 Tyrosine18. TyrosineTyr, (Y).

19 Tryptophan19. TryptophanTrp, (W).

Atif Hassan Khirelsied

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The imino acid

20. ProlinePro, (P).

The nitrogen atom is secondarily attached to the side‐


Atif Hassan Khirelsied

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The cystine

Atif Hassan Khirelsied

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Amino acids classification by solubility

• Two classes of amino acids based upon whether the R‐group is;R group is;

•1 H d h bi1. Hydrophobic 

2. Hydrophilic. 

Atif Hassan Khirelsied

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Amino acid classification by dietary importance.

Some amino acids can be formed from metabolic 

intermediates in the mammalian cells thus are notintermediates in the mammalian cells, thus are not 

necessary taken in food (Dietary non‐essential) .

Other amino acids must be obtained from diet, thus 

they are termed (Dietary essential).

Atif Hassan Khirelsied

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Amino acids classification by metabolic fate

Amino acids can also be classified according to the end product of their carbon skeleton catabolism into: p

1 Gluogenic glucose producing1. Gluogenic – glucose producing

2. Ketogenic – ketones producing

3. Keto and glycogenic.

Atif Hassan Khirelsied