Proteins are made up of amino acids and perform essential functions in the body. There are 20 amino acids that make up proteins. Amino acids contain an amino group, a carboxyl group, and a side chain. Proteins are classified by their biological functions and nutritional basis. Essential amino acids cannot be synthesized in the body and must come from dietary sources. When two amino acids bond together via dehydration synthesis, they form peptides.

1. Proteins
and
Amino Acids
Blithe
Topic:

2. Content:
1. Proteins:
a)Etymology
b)Classification by:
Biological functions, and
Nutritional Basis.
c)Sources
d)Importance
2. Amino Acids
a)Nature of Amino Acids
General Formula of Amino Acids
The20 Amino Acids, and
Classification
Peptide Formation

4. Proteins:
-the most abundant
organic molecule of the
living system , and
constitute about 50% of
the cellular weight.
-It’s name was derived
from the Greek word
“Proteios” which means
“Primary” or “Holding
the First Place”.
-A protein is a biological
molecule that consists of
one or more
polypeptides, which
are chains of polymerized
amino acids.

5. Protein
Composition
- basically, all
proteins contain
carbon, hydrogen,
oxygen, and
nitrogen.
Carbon: 48.2%
Hydrogen: 7.8%
Oxygen: 24%
Nitrogen: 16%
Sulfur: 4%Structure of sperm whale
myoglobin determined by
S. E. V. Phillips.

6. Classification of Proteins:
Class BiologicalFunction Sample Proteins
1. Contractile Protein Provide Motion or
movement of Muscle.
Actin and Myosin
2. Defense Protein Protection against foreign
bodies.
Antibodies and Toxic
Proteins
3. Enzymes Catalysis and inhibitor of
almost all the reaction of
living cell.
Digestive enzymes
4. Regulatory Protein Control of cell processes. Hormones like Insulin
and Oxytocin.
5. Storage Protein Store nutrients for
organism.
Casein , Albumin, and
Ferritin.
6. Structural Protein Mechanical support for
organism’s structure.
Fibrin, collagen, elastin,
and keratin.
7. Transport Protein Facilitates transport of
chemicals in body.
Hemoglobin and
Lipoproteins.

7. Classification of Proteins ona nutritional Basis
a. Complete Protein- supplies allthe essential amino acids.
b. Incomplete Proteins- deficient in one or more essential
amino acids.
Continuation…

8. Sources of Proteins…
-Dairy Products.
-meat
-Vegetables
-Fruits
-eggs,and otherprotein
rich foods.
Sourcesof Proteins…

9. Biochemicalconnectionof Proteins…

13. On a farm in Wyoming, USA, goats are being
milked for their spider web

14. Amino
Acids
14

15. Nature of Amino Acids
an amino acid is a small molecule
containing 4 different groups attached to
α- carbon.
15
R
|
H2N – C – COOH
|
H
Side Chain
Carboxyl
Group
Hydrogen Group
Amino group

16. The 20 Amino Acids
16

17. 17
cont…

18. 18

19. Naming Amino Acids
19

20. Properties of AminoAcids
1. Amino acids contain acidic (COOH) and basic (NH2)
groups.
 Therefore, amino acids have amphoteric properties:
 –In acidic medium ; the amino acid is positively
charged, so it behaves as a base (proton
acceptor).
 –In alkaline medium ; the amino acid is negatively
charged, so it behaves as an acid (proton donor).
20

21. cont… 21
2. Chirality
 handedness (from the Greek word “cheir, “hand”), which
results from the asymmetry of the alpha carbon.
Amino acids, except for Glycine, have at least one chiral
center.
H
|
H2N – C – COOH
|
H
Structural Formula of
Glycine

22. 3. Solubility
 The solubilities of
amino acids in water
are highly variable.
 extremely soluble like
Alanine, and some
are significantly less
soluble such as
cystine and tyrosine.
 Soluble in water,
acids, alkalis but
insoluble in organic
solvents.
22cont…

23. Classification of Amino Acids
 Amino acids can be classified in 2 ways:
1. Based on the side chain characters
2. Based on nutritional requirements
23
Classificationbased on side chaincharacters
1. Amino Acids with a Non-polar side-chain:
Has nonpolar side chains that interact very
weakly or not at all with water.
e.g.: Alanine, Valine, Leucine, Isoleucine,
Phenylalanine, Tryptophan, Proline

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25. 2. The Polar Amino Acids
25
can interact with water because they contain
hydrogen- bonding groups.
e.g. Serine, Threonine, Tyrosine,
Cysteine, Asparagine and Glutamine.

26. 3. Acidic Amino Acids
26
An amino acids which contain carboxyl
groups in their side chains in addition to the one
present in all amino acids.
e.g. Glutamic acid and Aspartic acid.

27. 4. Basic Amino Acids
27
An amino acids which contain amino groups
in their side chains in addition to the one present
in all amino acids.
e.g. Lysine, Arginine and Histidine

28. Classification Based on NutritionalRequirements
28
I. Essential amino acids:
These amino acids cannot be
synthesized in the body and have to
be present essentially in the diet.
Examples:
Valine, Isoleucine, Leucine, Lysine,
Methionine, Threonine, Tryptophan and
Phenylalanine.

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II. Semi-essential amino acids:
These amino acids can be
synthesized in the body but the
rate of synthesis is lesser than
the requirement(e.g. during
growth, repair or pregnancy)
Examples:
 Arginine and Histidine.

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III. Non-essential amino acids:
These amino acids are
synthesized in the body, thus
their absence in the diet does
not adversely affect the growth.
Examples:
 Glycine, Alanine, and the
other remaining amino acids.

31. Peptide Formation
31
When two amino acids are linked or joined
together it forms peptides.
This happen when the carboxyl group of one
amino acid made contact with the amine
group of another amino acid.
H R O
| | ||
H-N – C – C-OH
|
H
H R O
| | ||
H-N – C – C-OH
|
H
Cite of dehydration process
H R O
| | ||
-N – C – C-OH
|
H
H R O
| | ||
H-N – C – C-
|
H
-H2O

32. 32
H R O
| | ||
H-N – C – C-
|
H
H R O
| | ||
-N – C – C-OH
|
H
Amino acids in the peptide is called Amino Acid
Residues (the yellow shaded part).
Peptide Bond – the bond that joined the two
amino acids
Functional Grouped: Carbonyl Group and Amide
Group (the blue-green shaded part) .
Peptide can be classified into dipeptides,
tripeptides, tetrapeptides, Oligopeptides, and
Polypeptides.

33. Extra Scoopof Knowledgeabout Proteins/
AminoAcids. 
33
“Weird” Facts about Proteins…
 Proteins can have a bizarre names: For example: The protein
“Pikachurin” is a retinal protein that was named after
Pokemon character Pikachu.
Without a proteins called Albumin, the entire body would
swell.
Cataracts are caused by the denaturation of proteins in the
lenses of the eyes.

34.  Insects are more nutritious than many other common forms
of proteins. For example: 100 grams of top sirloin beef
contain 29 grams of proteins and 21 grams of fats. While in
100 grams of grasshopper contains 20 grams of proteins
and just 6 grams of fat.
 A protein in semen acts on the female brain to prompt
ovulation.
 A typical human male ejaculation contains about 150mg of
proteins.
 Having too much intake of proteins can be dangerous to the
body.
 Without protein, life is impossible to exist!
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