Proteins

Question 1

Structures

Answer 1

Primary-linear sequence of a.a
Secondary-spacial arrangement by twisting
Tritiary-3D structure
Quaternary- spacial arrangement of 2 or more polypeptide chains as subunits

Question 2

Primary structure

Answer 2

*largely responsible for its function
*abnormalities in a.asequence causes genetic diseases
*determine physical and chemical properties

Question 3

A.a held together by which bond

Answer 3

Peptide bond

Question 4

Bond which act as a cementing material bw a.a

Answer 4

Peptide bond

Question 5

Dipeptide has 2 peptide bond.true?

Answer 5

No
Dipeptide-2 a.a and 2 peptide bond
Polypeptide-more than 10

Question 6

Configuration of peptide bond

Answer 6

Trans

Question 7

Structure of peptide

Answer 7

Left n terminal ,korch a.a ,c terminal
If an,ine ,ate present make it yl except at c terminal
*2 adjacent carbon atom present at .36 nm

Question 8

3 steps to determine primary structure

Answer 8

1,a.a composition determine
2,polypeptide smaller fragments determine
3,a.a sequence determine

Question 9

Determination of a.a composition

Answer 9

*proteins-hydrolyse(acid/alkali/enzyme) to form a.a
*enzyme used-pronase( mixture of non specific proteolytic enzyme)
*separated by chromatographic techniques

Question 10

Properties of proteins

Answer 10

Soluble in colloidal soln than true soln bcz of its larger size of particles

Question 11

Properties of proteins

Answer 11

Soluble in colloidal soln than true soln bcz of its larger size of particles

Question 12

Precipitation of proteins, properties

Answer 12

Proteins, hydration of polar group us there
So exist in colloidal solutions
By dehydration/ neutralization it can be ppted

Question 13

Types of pptn of proteins

Answer 13

1,At pl
2,By salting out
3,By salts of heavy metals
4, By organic solvent
5,By alkaloid reagents

Question 14

Pptn at pl

Answer 14

Generally least soluble
Eg,casein easly ppted at pH of pl

Question 15

Pptn by salting out

Answer 15

Addtn of neutral salts such as nh3 sulfite/ na sulfate
Principle-dehydration of protein molecule by salt
Protein protein interaction^-molecular aggregation-precipitation

Pptn Amount of salt depends on size of particles
*size/weight ^lower salt is needed
Eg,globulin( half saturation)
Albumin (full saturation)

Question 16

Pptn by salts of heavy metals

Answer 16

Heavy metals(+ve charge) +protein solution in alkaline medium(-ve charge) =ppt formation
Eg,lead,hg ,fe,zn,cd

Question 17

By organic solvent

Answer 17

Good protein ppting agents
Dehydrate protein by removing h20 envelope and ppt
Eg alcohol

Question 18

By alkaloid agents pptn

Answer 18

Proteins trichloroacetic acid,sulphosalicykic,phosphotungstic acid,picric acid,tannic, phospho molybdic

By addtn of acids, proteins (cations) ppted by anionic to form;
Protein sulphosalicate
Protein tungstate
Protein picrate

Question 19

Denaturation

Answer 19

-disorganization of native Protein
-loss of 2o,3o and Quaternary structure
-change in physical, chemical and biological ppprty

Agents
Physical agents-heat, uv radiation, violent shaking, x rays
Chemical agents-acids ,alkalis,organic solvent, salts of heavy metals, urea, salicylate

Question 20

Characteristics of denaturation

Answer 20

-native helical structure is lost
-1o structure with peptide bond remain intact
-loss Biological properties
-denatured become insoluble in which earlier is soluble
-viscosity (eg honey) ^,surface tension (eg h20)decrease
-is irreversible bt sometimes reversible by renaturation
-is more easily digested
-cannot be crystallized