Protein is essential for building and repairing tissues, producing enzymes and hormones, and maintaining overall health. Good sources include meat, poultry, fish, eggs, dairy, legumes, nuts, and seeds. How can I assist you further with protein Proteins can be classified based on various criteria, including their structure, function, and source. Structurally, proteins are categorized into four primary levels: 1. Primary structure: The sequence of amino acids in a protein chain. 2. Secondary structure: Local folding patterns such as alpha helices and beta sheets. 3. Tertiary structure: The overall 3D shape of the protein molecule. 4. Quaternary structure: The arrangement of multiple protein subunits, if applicable. Functionally, proteins can be classified based on their roles in the body, such as enzymes, structural proteins, hormones, antibodies, transport proteins, and more. Finally, proteins can also be classified based on their source, such as animal proteins (found in meat, dairy, eggs) and plant proteins (found in legumes, nuts, seeds). Let me know if you need more details on any specific classification! Proteins play crucial roles in the body, serving as building blocks for tissues, enzymes for biochemical reactions, hormones for signaling, antibodies for immune defense, and transporters for molecules across cell membranes. Without adequate protein intake, various physiological functions would be impaired, leading to health issues. Thus, ensuring sufficient protein intake is essential for overall health and well-being. Protein is an essential macronutrient in our diet, crucial for building and repairing tissues, supporting immune function, and regulating various processes in the body. In terms of nutrition, it's important to consume an adequate amount of protein daily, with recommendations varying based on factors like age, sex, weight, activity level, and overall health status. For most adults, the recommended dietary allowance (RDA) for protein is around 0.8 grams per kilogram of body weight per day. However, individual protein needs may vary, and some individuals, such as athletes or those recovering from injury, may require higher protein intake. It's also essential to consume a variety of protein sources to ensure you get all the essential amino acids your body needs. Good sources of protein include lean meats, poultry, fish, eggs, dairy products, legumes, nuts, seeds, and tofu. Incorporating protein-rich foods into meals and snacks throughout the day can help maintain muscle mass, support satiety, and contribute to overall nutritional balance. If you have specific dietary goals or health concerns, consulting with a registered dietitian or nutritionist can help tailor your protein intake to meet your individual needs. Dietary sources of protein include a wide range of foods, both from animal and plant sources. Here are some common examples: 1. **Animal Sources**: - Meat: Beef, pork, lamb, veal, etc. - Poultry: Chicken, tur

1. CLASSIFICATION, FUNCTIONS,
COMPONENTS AND REQUIREMENTS
OF PROTEINS
SEMINAR BY
DR IRANNA ANGADI
1ST YEAR PG

2. CLASSIFICATION,FUNCTIONS,COMPONENTS
AND REQUIREMENTS OF PROTIENS
CONTENTS
 Introduction
 Why are proteins important to us:
 Levels in Protein structure
 Classification of Protein
 Functions of Protein
 Components of Protein
 Requirements of Protein
 References

3. Introduction
• Protein name is derived from a Greek word PROTOS which
means “the first or supreme”.
• Protein are extremely complicated and nitrogenous molecule
made up of variable number of amino acid residue joined to
each other by a specific covalent bond called peptide bond.
• 20 amino acid which have been found to occur in all
proteins, known as standard amino acid.

4. Why are proteins important to us:
• Proteins make up about 15% of the mass of the average person.
• Enzyme act as a biological catalyst.
• Storage and transport – Hemoglobin.
• Defence –Antibodies.
• Hormones - Insulin.
• Ligaments and arteries (mainly formed by elastin Protein).
• Muscle - Proteins in the muscle respond to nerve impulses by
changing the packing of their molecules (Actin and myosin).
• Hair, nails and skin: Protein keratin as main component.

5. Levels in Protein structure
• Majority of protein are compact and highly convoluted
molecules.
• Each polypeptide assumes at least three levels of structural
organization termed as primary, secondary and tertiary
structure.
• Proteins which possess more than one polypeptide chain in
their molecule also possess a fourth structure called quaternary
structure.

6. Chemistry of Protein Structure

7. Primary structure
• The sequence of amino acid residues along the peptide is called
primary structure of the peptide.
• It also include the determination of the number of amino acid residues
in a peptide chain.
• Shows whether the peptide chain is open, cyclic or branched.
• Primary structure is linear, ordered and 1 dimensional.
• Written from amino end to carboxyl end that is N to C.
Primary structure of human insulin
• CHAIN 1: GIVEQ CCTSI CSLYQ LENYC N
• CHAIN 2: FVNQH LCGSH LVEAL YLVCG ERGFF УТРКТ

8. Secondary Structure
• Primary structure shows that peptide are quite straight and extended.
• X-rays diffraction on protein crystals shows that polypeptide chain tend to twist or
coil upon themselves.
• The folding of the polypeptide chain into specific coiled structure held together by
H bonds is called secondary structure of protein
• Secondary structure may take one of the following form.
1. Alpha(a)- Helix
2. β- Pleated Sheath
3. Loop or Coil Conformation
4. Super secondary motifs

9. Alpha(a)- Helix
1. It is a clockwise rodlike spiral
shape.
2. Formed by intrachain Hydrogen
bonding between C=O group of each
amino acid and NH2 group that is
present 4 residue ahead.
3. Protein have great strength and
elasticity.
4. Can easily be stretched due to tight
coiling.

10. β- Pleated Sheath
1. 5 to 10 amino acid in this
structure line up side by side just
like a sheath of cloth can be folded
again and again
2. Hydrogen bond present
between the peptide strands that is
interstrand.
3. This form is fully expended and
can't be further stretched and they
are inelastic.

11. Loop or Coil Conformation
1. Present mainly in globular
protein.
2. Connect two Alpha helix or Beta
sheath.
3. Present in those area where
bend is required.

12. Super secondary Motifs
1. Present in Globular protein.
2. This structure form when two beta pleated sheath are connected to each
other by an alpha helix.
3. For example ẞ-a-ẞ supersecondary motif.

13. Tertiary structure
1. The tertiary structure mean the overall
conformation of a polypeptide.
2. Myoglobin chain is when fully
extended its length is 20 time than is
width.
3. X-rays diffraction show that its
structure is just like a foot ball i.e.
globular.
4. The globular structure is due to folding
and refolding

14. Quaternary Structure
1. Formed by those protein having
more than one peptide chain subunit.
2. Each peptide have its own primary,
secondary, and tertiary structure.
3. The number and arrangement of
the over all structure of the peptide
subunit is called quaternary structure.
4. For example structure of
Hemoglobin.

15. Classification of Protein
1.Classification based on shape
2. Classification based upon Function

16. Classification based on shape
Depend upon the axial ratio the protein are classify
into two type of protein.
1. Fibrous Protein
2. Globular Protein

17. Fibrous Protein
• Fibrous proteins are made up of elongated or fibrous polypeptide chains which form
filamentous and sheet-like structures.
• Axial ratio more than 10.
• Long thread like molecule.
• Their helical strands mainly form fibers.
• These protein are insoluble in water.
• Form structure of the tissue
• Present where support is required.
• Example
1.Collagen
2. Elastin
3. Keratin

18. Globular Protein
A Globular protein is a Spherical or Globular shaped protein, made by the
folding of different segments of a poly-peptide chain.
• Axial ratio less than 10.
• Spheroid or ovoid in shape.
• Enzyme are mostly globular in shape.
• Subdivided into two type of protein...
1. Albumins: Water soluble.
2. Globulin: Soluble in dilute salt solution

19. Classification based upon Function
• Catalytic Protein: These are enzyme which may be simple or conjugated.
1. Alkaline phosphatase
2. Alanine transaminase
• Regulatory or Hormonal protein: Many protein and peptide acts as Hormone.
1.Insulin
2.Growth Hormone
• Structural Protein: Contribute to the structure of the tissue.
1.Collagen
2. Elastin

20. Continue...
• Transport Protein: Serve to carry substances.
1. Transferrin carry Iron
2. Hemoglobin carry Oxygen
• Immune Protein: Serve in defense mechanism
1. Immunoglobulin, IgG, IgA, IgM, IgD, IgE
• Contractile Protein: Takes part in the muscle contrection.
1. Actin
2. Myosin

21. Continue...
• Genetic Protein: Protein present in combination with
nucleic acid.
1. Histone Protein.
• Storage Protein: To store protein for nutritional
purposes.
1. Casein in Milk
2. Gliadin in Wheat.

22. Protein metabolism
• Protein metabolism denotes the various
biochemical processes responsible for the
synthesis of proteins and amino acids
• The steps of protein synthesis include
transcription, translation, and post translational
modifications

23. PROTEIN FUNCTION
Protein helps repair and build your body’s tissues. It drives metabolic
reactions, maintains pH and fluid balance, and keeps the immune system
strong. It also transports and stores nutrients and can act as an energy
sourores nutrients and can act as an energy source.

24. Functions of Protein
Function Description Example
Antibody Antibodies
bind to specific
foreign
particles, such
as viruses and
bacteria, to
help protect
the body.
Immunoglobulin G (IgG)

25. Function Description Example
Enzyme Enzymes carry out
almost all of the
thousands of
chemical reactions
that take place in
cells. They also
assist with the
formation of new
molecules by
reading the genetic
information stored
in DNA.
Phenylalanine hydroxylase

26. Function Description Example
Messenger Messenger
proteins, such as
some types of
hormones,
transmit signals to
coordinate
biological
processes
between different
cells, tissues, and
organs.
Growth hormone

27. Function Description Example
Structural
component
These
proteins
provide
structure
and support
for cells. On
a large scale,
they also
allow the
body to
move.
Actin

28. Function Description Example
Transport/storage These
proteins
bind and
carry atoms
and small
molecules
within cells
and
throughout
the body.
Ferritin

29. Components of protein
• All proteins are made up of different arrangements of the same 20
kinds of amino acids
• Amino acids are the monomers that make up proteins. Each amino
acid has the same fundamental structure, which consists of a central
carbon atom bonded to an amino group (–NH2), a carboxyl group (–
COOH), and a hydrogen atom. Every amino acid also has another
variable atom or group of atoms bonded to the central carbon atom
known as the R group.
• The R group is the only difference in structure between the 20 amino
acids; otherwise, the amino acids are identical.

30. ‘
• The chemical nature of the R group determines. the chemical nature
of the amino acid within its protein (that is, whether it is acidic, basic,
polar, or nonpolar).

31. Requirements of Protein
0.8 grams per kilogram of body weight
Protein
RDA (g/kg/d)
Body weight (kg)
Protein
RDA (g/kg/d
Adult man Sedentary
Moderate
Heavy work
65 0.83
Adult woman Sedentary
Moderate
Heavy work
55 0.83

32. During pregnancy
• The recommended dietary allowance (RDA) for protein during the
first trimester of pregnancy is estimated at 46 g/day (0.8 g/kg
bw/day), and at 71 g/day (1.1 g/kg bw/day) during the second and
third trimesters [3].

33. DAILY PROTEIN REQUIREMENTS – MINIMUM
AMOUNT of PROTEIN to AVOID PROGRESSIVE
NITROGEN LOSS

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38. References
• C. Branden, J. Tooze. "Introduction to Protein Structure." Garland Science Publishing, 1999.
• C. Chothia, T. Hubard, S. Brenner, H. Barns, A. Murzin. "Protein Folds in the All-ẞ and ALL-a Classes."
Annu. Rev. Biophys. Biomol, Struct., 1997, 26:597-627.
• G.M. Church. "Proteins 1: Structure and Interactions." Biophysics 101: Computational Biology and
Genomics, October 28, 2003.
• C. Hadley, D.T. Jones. "A systematic comparison of protein structure
• classifications: SCOP, CATH and FSSP." Structure, August 27, 1999, 7:1099-1112.
• S. Komili. "Section 8: Protein Structure." Biophysics 101: Computational Biology and Genomics,
November 12, 2002.
• D.L. Nelson, A.L. Lehninger, M.M. Cox. "Principles of Biochemistry, Third Edition." Worth Publishing, May
2002.
• pdb animation created with PDB to MultiGif, http://www.dkfz-heidelberg.de/spec/pdb2mgif/expert.html

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