Hemoglobin

Question 1

What are the Kd of oxygen and carbon monoxide in heme, Mb and in the atmosphere

Answer 1

Question 2

What kind of hybridisation does the carbon atom undergo in carbon monoxide

Answer 2

Sp hybridisation

Question 3

Draw the molecular orbital diagram for carbon monoxide

Answer 3

Question 4

What is the bond order of carbon monoxide

Answer 4

3
Carbon is partially negative, oxygen is partially positive
This allows carbon monoxide to bind to iron as a ligand

Question 5

What is the proximal histidine

Answer 5

It is bound to iron in heme
It is an axial ligand

Question 6

What is the distal ligand in myoglobin

Answer 6

It is the histidine which isn’t a ligand (it isn’t bound to iron) and isn’t part of heme group but is present in myoglobin

Question 7

Why does carbon monoxide bind to the iron in heme tipped

Answer 7

The distal histidine causes the carbon monoxide to tip when binding to iron as it is in the way
This is why carbon monoxide has a lower affinity to myoglobin

Question 8

What are the different arrangements of d orbitals for iron

Answer 8

Question 9

Show the distribution of electrons in atomic orbitals in ferric iron

Answer 9

Question 10

Show the distribution of electrons in ferrous iron

Answer 10

Question 11

Which of the arrangements of d orbitals in iron are most energetically favourable and why

Answer 11

Irons own electrons aren’t pointing towards the ligands
So the electrons from the ligands aren’t being repelled by irons electrons
Therefore this is a low energy conformation

Question 12

Which of irons arrangement of d orbitals are energetically unfavourable and why

Answer 12

Irons electrons are pointing towards equatorial ligands for x squared and towards the axial ligands for a squared which would repel the ligands electrons
Energy would be needed to overcome repulsion

Question 13

Show the filling of electrons in the 3d orbital of Fe2+

Answer 13

Question 14

Show the filling of electrons in the 3d orbital of Fe2+ in heme

Answer 14

Question 15

Show the filling of electrons in the 3d orbital of Fe2+ in myoglobin and what is it called

Answer 15

Question 16

Show the filling of electrons in the 3d orbital of Fe2+ in myoglobin when oxygen is bound for each type of d orbital arrangement for iron

Answer 16

Question 17

How is iron orientation for ‘high spin’

Answer 17

Iron is below the plane of the equitorial ligands so wont line up its electrons directly with the electrons of nitrogen

Question 18

What is the protein conformation change that occurs when oxyge binds to iron in heme

Answer 18

Iron moves when oxygen is bound: it lines up with the equitorial nitrogen atoms (lines up with the plane)
Proximal histidine also moves with the iron
Therefore it pulls the helices that histidine is attached to with it which changes the shape of the protein

Question 19

What is cooperatively

Answer 19

One subunit in a protein changes which causes a change in other subunit

Question 20

What is the oligomeric structure of hemoglobin (how is it represented)

Answer 20

Question 21

What is allosteric change

Answer 21

Change in shape (change in conformation) due to rotations around single bonds

Question 22

How does oxygenation of heme change the structure of hemoglobin

Answer 22