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Structure & Classification of Proteins. Dr. Bibi Kulsoom. Proteins. Other dry elements 14%. Proteins: Amino Acids. Peptide bond.

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Structure & Classification of Proteins

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Structure & Classification of Proteins

Dr. Bibi Kulsoom


Other dry elements 14%

Proteins: Amino Acids

Peptide bond

One Amino acid structure

Protein molecule

Hydrolysis by digestive enzymes

Amino acids

Hydrocarbon chain

Proteins are Composed :

of 20 Amino Acids

  • Essential amino acids

  • Arginine (partially essential)

  • Histidine

  • Isoleucine

  • Leucine

  • Lysine

  • Methinine

  • Phenylalanine

  • Threonine

  • Tryptophan

  • Valine

  • Non-Essential amino acids

  • Alanine

  • Aspartic acid

  • Asparagine

  • Cysteine

  • Glutamic acid

  • Glutamine

  • Glycine

  • Proline

  • Serine

  • Tyrosine

Proteins & their Classification

Classification is based on

  • Composition

  • Shape

  • Function

Classification Based on Composition

  • Simple proteins:

    A protein that contains amino acids only.

    Examples: albumin, globulins & histones.

  • Conjugated Proteins:

    A protein that have some non-protein moiety in its structure along with protein part.

  • Derived proteins:

    Proteins derived from simple and conjugated proteins by physical or chemical treatment. Examples: peptones peptides and denatured proteins.


Proteins examples:

Histones, telomerase.


Proteins examples:

Glycoproteins of cell membrane, Follicle-stimulating hormone (FSH), Luteinizing hormone (LH).


Proteins examples:

Low density lipoprotein (LDL), high density lipoprotein (HDL).


Proteins examples:

Enzymes (protein in nature) are phosphorylated temporarily for their regulation.

Enzyme A

Enzyme B

Enzyme A





Enzyme B



Cytochromes P450


Proteins examples:

Hemoglobin, cytochromes (enzymes).


Proteins examples:

Hemoglobin, Ceruloplasmin (protein that stores and transports copper)



Based on Shape

Globular Proteins

Hemoglobin and myoglobin are examples of globular proteins.

Fibrous Proteins or Scleroproteins

Collagen, keratin and elastin are examples of fibrous proteins.

Collagen fiber



Classification based on Function

Structural Proteins

Proteins gives our cells shape, strength as well as enable movements.

Proteins examples:

keratin, collagen, elastin.

Structure Examples:

Hair, wool, nails, horns, hoofs, tendons, cartilage.

Contractile Proteins

Proteins examples:

Actin & myosin

Location in body:

Contracting fibers in muscle.

Transport Proteins

  • Protein examples:

  • hemoglobin (Carries oxygen in blood)

  • serum albumin (Carries fatty acids in blood)

Storage Proteins

  • Proteins examples:

  • Different for different sustances.

  • Ferritin (Stores iron in spleen)

  • legumes and beans in plants

Proteins as Enzymes

  • Many proteins act as biological catalysts or enzymes.

  • Thousands of different enzymes exist in the body.

  • Examples: catalase, amylase, trypsin, lipase.

Immunological Proteins

  • Proteins examples:

  • Gamma globulins

  • when a pathogen enters the body, the immune system produces antibodies against it that fight against the invader.




Proteins as Buffers


Plasma proteins and intracellular preoteins.

Maintaining Osmotic Pressure

  • Protein examples:

  • Albumin, globin, globulin.


Protein as Hormone

Examples: Insulin, glucagon, growth hormone etc.

Protein Channels & Receptors

Cell cytoskeleton

Channels: Protein pores that run like tunnels across the lipid bilayer will allow specific materials that we need, like glucose, to slip through the membrane.

Receptors: proteins that mediate the effects of hormones in side the cell.

Examples: Microfilaments, intermediate filaments & microtubules.

Clotting Factors

Clotting proteins activate and make meshwork of fibrin to stop bleeding. Examples:

Factors I, II, III, IV, V etc.


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