GP

Question 1

Heme is a ?

Answer 1

Prosthetic group

Question 2

Structure of heme

Answer 2

Planar
Porphyrin ring w/ Fe2+ in its centre

Question 3

Bonds formed by Fe2+ in heme

Answer 3

6 bonds formed =
4 with porphyrin nitrogen’s
+
2 additional - with histidine residue of glob in molecule
- for O2 binding

Question 4

The main primary protein structure found in MYOGLOBIN

Answer 4

Alpha helix - 8 stretches found
~80% of its PP chain

Question 5

The alpha helical regions are terminated by the presence of

Answer 5

Proline (since it’s 5 membered ring can’t be accommodated in an alpha helix)
Or by beta bends
And loops are stabilised by H & IONIC bonds

Question 6

Interior of Mb composed of

Answer 6

Non polar amino acids - closely packed together
Forming stabilised structure with the help of HYDROPHOBIC INTERACTIONS

Question 7

Surface of Mb composed of

Answer 7

Polar aa.
Forms H bonds w/ each other OR w/ water
= making it SOLUBLE

Question 8

Position of heme in Mb

Answer 8

Sits in a crevice line w/ NON POLAR aa

Question 9

The BASIC amino acids present in the crevice (exception here to the non polar aa. lining the crevice)

Answer 9

2 Histidine residues
- proximal histidine (F8) = binds to Fe2+ of heme group
- distal histidine (E7) = stabilises binding of O2 to Fe2+

Question 10

The amino acids mentioned before forms the

Answer 10

Protein/Globin portion of Mb

Question 11

Function of Globin portion of Mb is to

Answer 11

Create a special micro environment for heme
Helping it in OXYGENATION

Question 12

How many Oxygen molecules are carried by Mb?

Answer 12

1 O2

Question 13

Number of PP chains in Mb

Answer 13

1

Question 14

Number of PP chains in Hb

Answer 14

4

Question 15

The 4 PP chains in Hb are

Answer 15

2 alpha + 2 beta

Question 16

How are these chains held

Answer 16

By NON COVALENT INTERACTIONS

Question 17

The quaternary structure of Hb tetramer composed of

Answer 17

2 identical dimers alpha-beta1 & alpha-beta2

Question 18

The PP chains w/in each dimers are held tightly by

Answer 18

Hydrophobic interactions = STABLE STRUCTURE

Question 19

The hemoglobin found in HUMAN is

Answer 19

HbA

Question 20

Number of heme groups & oxygen molecules carried

Answer 20

4 heme groups + 4 O2 carried

Question 21

What else is transported by Hb

Answer 21

H+ and CO2

Question 22

Bonds b/w alpha-beta1 and alpha-beta2 dimers

Answer 22

Held mainly by POLAR BONDS,
Which are weak ionic & H bonds = permits movement -> different positions taken

Question 23

2 different positions due to this movement

Answer 23

In deoxyHb - T form (taut)
In OxyHb - R form (relaxed)

REMEMBER
O2 കിട്ടിയപ്പോൾ relaxed ആയി

Question 24

T-FORM aka deoxy form of Hb

Answer 24

Weak ionic and H bonds (the polar bonds) -> constrain the PP chains movement
Fe2+ gets pulled out of the heme structure
Low oxygen affinity form

Question 25

R-FORM aka oxy form of Hb

Answer 25

Polar bonds are ruptured b/w the alpha-beta dimers
Fe2+ moves into the heme planar structure
High oxygen affinity form