L6: Protein classification Flashcards
What are proteins?
Organic complex nitrogenous compounds of high molecular weight formed of C, H, O, N [N= 16%].
What is the biological importance of proteins?
1) Antibodies (immunoglobulin) are proteins
2) Buffer system of blood (plasma proteins).
3) Carry hormones and minerals in blood (plasma proteins), Carry oxygen (Hemoglobin).
4) Structure of cell membrane.
5) Support bone, skin, nails, and hair.
6) Hormones as insulin.
7) Enzymes are proteins.
What are proteins classified according to?
1) According to shape
2) According to Nutritional value
3) According to their chemical structure
What are the types of proteins according to shape?
Fibrous and globular
Fibrous proteins
-Long, narrow fibers
-More than 10
-Insoluble
-More stable
-Actin, Myosin, collagen
Globular proteins
-Rounded (spherical)
-Axial ratio Less than 10
-Soluble
-Less stable
-Albumin, hemoglobin, insulin
What are proteins classified to according to nutritional value?
-nutritionally rich proteins—>contain all the essential amino acids.
-incomplete proteins—->Lack one essential amino acid.
-poor proteins—->Lack many essential amino acids.
Give examples of proteins classified according to their nutritional value respectively.
1-caseinogen(protein of milk)
2-proteins of pulses lack methionine, proteins of cereals lack lysine.
3- zein of maize protein lacks lysine and tryptophan.
What are proteins classified into according to their chemical structures?
-simple, compound, and derived.
What are simple proteins?
On hydrolysis, they produce only amino acids.
Give examples for globular and fibrous simple proteins.
The first six are globular.
1-albumin
2-globulin
3-Glutillin
4-Prolamin
5-Protamin
6-histones
7-albuminoids(scleroproteins)
Albumin
Coagulated by heat
-present in egg (egg albumin),blood (plasma albumin)and milk (lactoalbumin)
Globulin
-Coagulated by heat
-present in egg (egg globulin), blood (plasma globulin), milk (lactoglobulin)
Glutellin
as glutenin of wheat.
Prolamin
-as Zein of corn and maize.
- deficient in tryptophan amino acid →
Protamin
-Rich in basic amino acids.
-found in combination with nucleus acid of Salomon.
Histones.
-rich in basic amino acids.
-found in combination with nucleic acids in human
-found in globin of HB.
Albumins
they are fibrous proteins.
Insoluble in water ,dilute acids and alkali and all neutral solvents.
Not digested by proteolytic enzymes.
Found in animal tissues and having supportive and protective functions.
Ex:
A. Keratin:present in hair, nail
B. Elastin: present in joints, wall of lung alveoli and ligaments
C. CollageN:present in skin, bone, cartilage, and connective tissues
What are conjugated proteins?
they are formed of protein and non-protein part.
Give examples for conjugated proteins
-Glycoproteins
-lipoproteins
Phosphoproteins
-metalloproteins
-Chromoproteins(hemo and flavo)
-Nucleoprotein
What are glyco proteins(much-proteins)?
proteins are conjugated with carbohydrates
Ex: Hormones (FSH, LH), Enzymes.
Mucin of GIT.
Antibodies, blood group Antigen. .
What are lipoproteins?
proteins are conjugated with lipids.
Ex: Chylomicrons VLDL
LDL, HDL.
What are phosphoproteins?
Proteins are conjugated with phosphoric acid.
Ex: Caseinogen (main protein of milk).
What are metalloproteins?
Proteins are conjugated with metals.
Ex: Ceruloplasmin (protein + Cu).
Insulin (protein + Zinc).
Ferritin (Fe)
What are chromatoproteins?
-Hemoproteins
-Flavoproteins
What is hemoproteins?
protein + heme (red pigment)
as Hemoglobin and cytochromes (components of electron transport chain)
What are favoproteins?
proteins + FAD (yellow color).
What are nucleoproteins?
Proteins are conjugated with nucleic acids.
Ex:
Histone + DNA in chromosome.
protein + RNA in Ribosome.
What are derived proteins
they are denaturated or hydrolytic products of simple or conjugated proteins .
What are the types of derived proteins ?
Primary and secondary
What are primary derived proteins?
result from of proteins from its native state without hydrolysis of peptide bond
Ex:-meta which are produced by hydrolysis with a cid or alkali
Coagulated which result from hydrolysis with heat
What are secondary derived proteins?
They are hydrolysis products of proteins.
Proteomes: Products of partial hydrolysis of proteins
Peptones: Products of proteoses hydrolysis.
Peptides: Products of peptones hydrolysis.
