1. Ass.Prof./Naglaa Fathy Alhusseini
Protein Chemistry
Ass.Prof./Naglaa Fathy Alhusseini
4/24/2017
Naglaa Alhusseini

2. Proteins chemistry Definition:
Proteins are organic nitrogenous compound of high molecular weight, consisting largely or entirely of α-amino acids united together by peptide linkages.
They are composed of carbon, hydrogen, oxygen and nitrogen, many types of proteins may contain sulfur.
Nitrogen is a characteristic component of proteins, forming about 16% of their weight.
4/24/2017
Naglaa Alhusseini

3. Functions of proteins:
Synthesis of tissue proteins e.g., contractile protein of muscles, collagen …etc...
Synthesis of cell organelles as cell membrane ,receptors…….etc
Synthesis of enzymes
Synthesis of milk proteins.
Synthesis of plasma proteins.
Synthesis of protein hormones.
Synthesis of nucleoproteins.
4/24/2017
Naglaa Alhusseini

4. Biological importance of proteins:
Fibrous or structural protein
Keratin- elastin
Collagen- reticulin
Muscle protein (Myocin and Actin)
Protein of cell membrane
Protein of cytoplasm
Functional protein
Enzyme
Hormones
Receptors
Igs
Plasma protein
Hemoglobin
4/24/2017
Naglaa Alhusseini

5. Questions 1- What are the biological importance of proteins?
All the following are functional protein EXCEPT
Igs
enzyme
Collagen
Hemoglobin
4/24/2017
Naglaa Alhusseini

6. Amino Acids
Amino acid is an organic acid containing one or more amino group and carboxylic group (COOH)
carboxylic group (COOH) and amino group (NH2) are both attached to the α-carbon
They are the building units of protein.
4/24/2017
Naglaa Alhusseini

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Naglaa Alhusseini

8. D-amino acid L-amino acid
Amino acids found in proteins are of L-configuration, this means that the amino group to the left and the hydrogen to the right of the a-carbon
D-amino acid
L-amino acid
Isomerism of amino acids
4/24/2017
Naglaa Alhusseini

9. Functions of amino acids: Question
Synthesis of structural and functional proteins.
L-amino acid and their derivatives play a role in intracellular functions as nerve impulse transmission and regulation of cell growth.
Biosynthesis of purines, pyrimidines, urea and porphyrins.
L-and D-amino acids are present in polypeptide antibiotics secreted by microorganisms.
True or false ??
4/24/2017
Naglaa Alhusseini

10. Classifications:
Amino acids can be classified by different classification:
Chemical classification.
Nutritional classification.
Metabolic classification.
Reaction classification (Charge properties).
4/24/2017
Naglaa Alhusseini

11. 1. Chemical classification:
A) Aliphatic amino acids: have no ring; These amino acids may be subclassified into:
Branched chain amino acids: as valine, leucine, and isoleucine.
Hydroxy amino acids: as serine and threonine.
Sulphur containing amino acids: as cysteine and methionine.
Amino acids with amide group: as asparagine and glutamine.
4/24/2017
Naglaa Alhusseini

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Naglaa Alhusseini

13. Glycine Alanine Valine Leucine Isoleucine
Gly - G
Alanine
Ala - A
Valine
Val - V
Leucine
Leu – L
Isoleucine
Ile - I

14. Serine Threonine Cysteine Methionine Cystine
Ser - S
Threonine
Thr - T
Cysteine
Cys - C
Methionine
Met - M
Cystine
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Naglaa Alhusseini

15. Aromatic amino acids Phenylalanine Phe - F Tyrosine Tyr - Y Tryptophan
Trp - W
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16. Heterocyclic amino acids: They have heterocyclic ring as histidine, tryptophan, proline and hydroxyproline.
Proline
Pro – P
Hydroxy proline
Hyp
4/24/2017
Naglaa Alhusseini

17. Reaction classification ( charge properties):
Non polar (Neutral): having equal number of amino and carboxyl groups
e.g. alanine, serine, valine …etc
Polar Basic AA: having more than one amino group and one carboxyl
e.g. arginine, lysine, histidine …etc
Polar (Acidic): having one amino group and two carboxyl
e.g. glutamic acid and aspartic acid
4/24/2017
Naglaa Alhusseini

18. Polar Basic AA: having more than one amino group and one carboxyl e. g
Polar Basic AA: having more than one amino group and one carboxyl e.g. arginine, lysine, histidine
Arginine
Arg - R
Lysine
Lys - K
Histidine
His - H
4/24/2017
Naglaa Alhusseini

19. Acidic Amino Acids and their Amides
Aspartic Acid
Asp - D
Asparagine
Asn - N
Glutamic Acid
Glu - E
Glutamine
Gln - Q
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Naglaa Alhusseini

20. C) Heterocyclic amino acids: They have heterocyclic ring as
B) Aromatic amino acids: They have benzene ring in their side chains like
Phenylalanine
Tyrosine
Tryptophan
C) Heterocyclic amino acids: They have heterocyclic ring as
Histidine,
Tryptophan,
Proline and hydroxyproline.
4/24/2017
Naglaa Alhusseini

21. 2. Nutritional classification:
They are classified into three groups:
Essential amino acids: They are amino acids which cannot be synthesized in the body and must be taken in diet; phenylalanine, methionine, isoleucine, leucine, lysine, valine, threonine and tryptophan.
Semi essential amino acids: They are amino acids required in the food of growing children not in the food of adult as histidine and arginine.
Non essential amino acids: can be synthesized inside the body as glycine, alanine, serine, cysteine, cystine, aspartic, tyrosine, glutamic, proline and hydroxyproline
4/24/2017
Naglaa Alhusseini

22. Memory Aid for Essential Amino Acids
Any Help In Learning These Little Molecules Proves Truly Valuable Arginine –Histedine – Isoleosine – Leosine – Threonine- Lysine- Methionine –Phyenylalanine- Tryptophan –Valine
4/24/2017
Naglaa Alhusseini

23. 3. Metabolic classification:
According to their fate in the body they are classified into three groups:
Glucogenic amino acids: give glucose inside the body as glycine, alanine, aspartic and glutamic.
Ketogenic amino acid: gives ketone bodies as leucine.
Glucogenic and ketogenic amino acids: They give both glucose and ketone bodies as lysine, tryptophan, tyrosine, phenylalanine and isoleucine.
4/24/2017
Naglaa Alhusseini

24. Clinical importance of amino acids and their derivatives
L-tyrosine is sometimes recommended by practitioners as helpful for weight loss, clinical depression.
Dopamine derived from tyrosine is a neurotransmitter.
Thyroxine is an important thyroid hormone from tyrosine.
Gamma aminobutyric acid (GABA) derived from glutamic acid; which is a neurotransmitter.
Cycloserine derived from serine is an anti-tuberculous drug.
Arginine stimulates the healing of burning wound and other wounds.
Arginine together with lysine can limit herpes attacks (bladders in the mouth) for people that carry this virus.
Cysteine can help to recover the damage by smoking and alcohol.
Glutamine can give the mind new energy and can help to prevent and treat inflammations of the large intestine.
4/24/2017
Naglaa Alhusseini

25. Which of the following amino acid is an acidic amino acid.
Arginine
Aspartic acid
Lysine
Leucine
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Naglaa Alhusseini

26. Which of the following amino acid is both neutral and aromatic in nature?
Alanine
Histidine
Plyenylalanine
Proline
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Naglaa Alhusseini

27. All amino acids which both glucogenic and ketogenic are essential amino acids EXCEPT
Phenylalanine
Tyrosine
Glycine
Alanine
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Naglaa Alhusseini

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Naglaa Alhusseini

37. Amino acid not found in proteins:
Few amino acids are not found in proteins (non-protein amino acids)
L-Ornithine is an intermediate of urea cycle . It is formed from arginine
L- citrulline is intermediate of urea cycle . It is formed from ornithine
Homoserine is an intermediate in methionine metabolism. It is formed from serine.
GABA: γ amino butyric acid :is an inhibitor neurotransmitter
DOPA: Dihydroxyphenylalanine : Is formed from tyrosine and precursor for biosynthesis of epinephrine and norepinephrine
β alanine : occurs in coenzyme A , Pantothenic acid and it is also formed during degeneration pyrimidine nucleotides
Selenocysteine is an amino acid containing selenium ( trace element). It is considered as the 21st amino acid since it is coded by the stop codon UGA. Examples of proteins containing selenocysteine are glutathione peroxidase enzyme and 5'deiodinase .
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Naglaa Alhusseini

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Naglaa Alhusseini