L6: Protein classification

Question 1

What are proteins?

Answer 1

Organic complex nitrogenous compounds of high molecular weight formed of C, H, O, N [N= 16%].

Question 2

What is the biological importance of proteins?

Answer 2

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.

Question 3

What are proteins classified according to?

Answer 3

1) According to shape
2) According to Nutritional value
3) According to their chemical structure

Question 4

What are the types of proteins according to shape?

Answer 4

Fibrous and globular

Question 5

Fibrous proteins

Answer 5

-Long, narrow fibers
-More than 10
-Insoluble
-More stable
-Actin, Myosin, collagen

Question 6

Globular proteins

Answer 6

-Rounded (spherical)
-Axial ratio Less than 10
-Soluble
-Less stable
-Albumin, hemoglobin, insulin

Question 7

What are proteins classified to according to nutritional value?

Answer 7

-nutritionally rich proteins—>contain all the essential amino acids.
-incomplete proteins—->Lack one essential amino acid.
-poor proteins—->Lack many essential amino acids.

Question 8

Give examples of proteins classified according to their nutritional value respectively.

Answer 8

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.

Question 9

What are proteins classified into according to their chemical structures?

Answer 9

-simple, compound, and derived.

Question 10

What are simple proteins?

Answer 10

On hydrolysis, they produce only amino acids.

Question 11

Give examples for globular and fibrous simple proteins.

Answer 11

The first six are globular.

1-albumin
2-globulin
3-Glutillin
4-Prolamin
5-Protamin
6-histones
7-albuminoids(scleroproteins)

Question 12

Albumin

Answer 12

Coagulated by heat

-present in egg (egg albumin),blood (plasma albumin)and milk (lactoalbumin)

Question 13

Globulin

Answer 13

-Coagulated by heat

-present in egg (egg globulin), blood (plasma globulin), milk (lactoglobulin)

Question 14

Glutellin

Answer 14

as glutenin of wheat.

Question 15

Prolamin

Answer 15

-as Zein of corn and maize.

• deficient in tryptophan amino acid →

Question 16

Protamin

Answer 16

-Rich in basic amino acids.

-found in combination with nucleus acid of Salomon.

Question 17

Histones.

Answer 17

-rich in basic amino acids.

-found in combination with nucleic acids in human

-found in globin of HB.

Question 18

Albumins

Answer 18

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

Question 19

What are conjugated proteins?

Answer 19

they are formed of protein and non-protein part.

Question 20

Give examples for conjugated proteins

Answer 20

-Glycoproteins
-lipoproteins
Phosphoproteins
-metalloproteins
-Chromoproteins(hemo and flavo)
-Nucleoprotein

Question 21

What are glyco proteins(much-proteins)?

Answer 21

proteins are conjugated with carbohydrates

 Ex: Hormones (FSH, LH), Enzymes.
 Mucin of GIT.
 Antibodies, blood group Antigen. .

Question 22

What are lipoproteins?

Answer 22

proteins are conjugated with lipids.

Ex: Chylomicrons VLDL
LDL, HDL.

Question 23

What are phosphoproteins?

Answer 23

Proteins are conjugated with phosphoric acid.

Ex: Caseinogen (main protein of milk).

Question 24

What are metalloproteins?

Answer 24

Proteins are conjugated with metals.

Ex: Ceruloplasmin (protein + Cu).

 Insulin (protein + Zinc).

 Ferritin (Fe)

Question 25

What are chromatoproteins?

Answer 25

-Hemoproteins
-Flavoproteins

Question 26

What is hemoproteins?

Answer 26

protein + heme (red pigment)

as Hemoglobin and cytochromes (components of electron transport chain)

Question 27

What are favoproteins?

Answer 27

proteins + FAD (yellow color).

Question 28

What are nucleoproteins?

Answer 28

Proteins are conjugated with nucleic acids.

Ex:
Histone + DNA in chromosome.

protein + RNA in Ribosome.

Question 29

What are derived proteins

Answer 29

they are denaturated or hydrolytic products of simple or conjugated proteins .

Question 30

What are the types of derived proteins ?

Answer 30

Primary and secondary

Question 31

What are primary derived proteins?

Answer 31

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

Question 32

What are secondary derived proteins?

Answer 32

They are hydrolysis products of proteins.

Proteomes: Products of partial hydrolysis of proteins

Peptones: Products of proteoses hydrolysis.

Peptides: Products of peptones hydrolysis.