protein

Question 1

what are proteins?

Answer 1

it is a large-sized macromolecule made up of one or more than one polypeptide.

Question 2

what is a polypeptide?

Answer 2

it is a chain of amino acids connected by peptide bonds. the word polypeptide is often interchangeably used with protein, but a polypeptide should at least e 50 amino acids long to qualify as a protein.

Question 3

what kind of polymer is protein.

Answer 3

It’s a polymer of amino acids, since there are 20 types of amino acids, protein is a heteropolymer of amino acids.

Question 4

what are the two types of protein?

Answer 4

1) monomeric: single polypeptide chain

2) oligopeptide; more than one polypeptide chain

Question 5

explain the primary structure of a protein?

Answer 5

1) linear arrangement of amino acids
2) 20 amino acids are arranged differently to give different proteins
3) it was first described by Friedrich sanger

Question 6

explain secondory structure?

Answer 6

1) given by Linus Pauling and Robert Corey

2) discovered in 2 forms: alpha-helix: right-handed and beta pleated sheeted

Question 7

explain the alpha helix: righht handed form.

Answer 7

• coiled toward the right
• every fourth amino acid is connected by the formation of an intramolecular hydrogen bond
• hydrogen bond keeps the chain together
• the intramolecular hydrogen bond is formed between hydrogen and highly electronegative atoms like nitrogen, oxygen and fluorine of another molecule
• found in alpha keratin component of hair, nails and hooves
• collagen helix: the polypeptide helix of collagen is straightened by establishing hydrogen bond and locking effect, also with help of proline and hydroxyproline amino acid.

Question 8

explain tertiary structure?

Answer 8

• the long polypeptide chain folds upon itself like a hollow wollen ball, this gives a 3D look of the proitein, this the tertiary structure
• this brings distant amino acid side chains closer forming an active site of protein which is enzyme.

eg: enzymes, myoglobin(muscle cells)

Question 9

what is an active site?

Answer 9

where a subtract is attached to.

Question 10

explain quaternary proteins.

Answer 10

• only present in oligomeric proteins
• discovered by Kendrew and pereutz 9in 1963
• founded in haemoglobin: 4 polypeptide chains(2 alpha chains and 2 beta chains)

Question 11

explain the structure of collagen protein.

Answer 11

• it is called triple helix/tripos helix/collagen helix/madras helix
• discovered by Dr . GN Ramachandran in 1954
• he proposed the Ramachandran plot to determine the structure of various proteins including collagen
• collagen provides structural support to various connective tissue

Question 12

what is the classification of protein, based on function?

Answer 12

1) transport protein: transport materials.
eg: haemoglobin: o2 and co2
Glute4: transports glucose in the presence of insulin
p-protein: transport material inside the phloem
transferrin: transport iron within the body

2) structural protein: helps in supporting and forming different body structures
eg: collagen: protein: most abundant protein in animals.
reticulin protein

3) regulatory protein: many proteinaceous hormones are responsible for body function regulation.
eg: glucagon and insulin: controls glucose level in blood

4) contractile protein: helps in relaxation and contraction of muscles.
eg: actin and myosin

5) visionary protein: helps in vision.
eg: rhodopsin,cyanopsin,chloropsin,erythropsin.

6) toxin protein: poisonous protein.
eg: venin(snake venom),abrin, ricin

Question 13

what is classification of protein based on chemical nature?

Answer 13

1) simple protein

2) conjugate protein

Question 14

explain simple protein.

Answer 14

: composed of only amino acids. they are water-soluble.
some are globular small proteins, water-soluble and not coagulated by heat(eg: histones). as the size increases, they become less water-soluble and increasingly heat coagulant t.larger globular proteins like egg albumin, serum globulin, glutelin(wheat or rice)are coagulated by heat.
fibrous proteins like keratin(hair) and collagen(connective tissue) are long molecules and are water-insoluble.

eg: 1) albumin:osmoregulation
egg albumin: storage
2)glutelin: storage protein wheat or rice
3) globulin: fight infection, blood clotting etc
4)histone: wound over DNA in chromosomes

Question 15

explain conjugate protein.

Answer 15

protein along with a non-protein part. this is formed by the binding of simple protein with a prosthetic group.
eg: 1)nucleoprotein: nucleaic acid + protein
2)metalloprotein: metal + protein. eg: ferretin
3)chromoprotein : pigment + protein . eg: cytochromes.
4)glycoprotein: sugar + protein
-follicle stimulating hormone
eg: mucin
-matrix of connective tissue
5)lipoprotein: lipid + protein
c-cell membrane in bacteria , egg yolk
eg:chylomicron
6)phosphoprotein: phosphate + protein
eg: ceasin (milk protein)

Question 16

classification protein based on nutritional requirements.

Answer 16

1) class1 protein: provide all essential amino acids
eg: animal protein
2) class 2 protein: does not provide all essential amino acids.
eg: plant protein:
1) cereals: lacks lysine and tryptophan
2) pulses: lacks methionine and cysteine

Question 17

what are enzymes made up of?

Answer 17

all enzymes are built upon simple proteins and conjugated proteins.
eg: trypsin(pancreatic)

Question 18

explain defence proteins.

Answer 18

immunoglobulins and antibodies are built upon proteins they are produced by B- lymphocytes

Question 19

what secretes insulin?

Answer 19

beta cells of islet of Langerhans of the pancreas

Question 20

receptors?

Answer 20

protein structure on the surface of the plasma membrane binds information molecules like hormones.. also in sense organs for detecting smell and taste

Question 21

what protein does antarctic fish contain?

Answer 21

antifreeze protein prevents their blood from freezing

Question 22

give an example of a serious disease caused by change in sequence of amino acids.

Answer 22

change of one glutamine by valine in haemoglobin can cause sickle cell anaemia.

Question 23

what is monellin?

Answer 23

a protein in the African berry plant, a noncaloric, non-toxic, non-flattening sweetener that is good for diabetic patients

Question 24

what did Fredrich sanger workout?

Answer 24

he worked out the sequence of amino acids in the polypeptide chain of the hormone insulin.

Question 25

which are the proteins used as therapeutic agents?

Answer 25

1) thrombin and fibrinogen: helps in blood clotting

2) streptokinase: produced by bacterium streptococcus, used as clot busters