Hemoglobin

Question 1

What is myoglobin for

Answer 1

oxygen binding protein

Question 2

where is myoglobin found

Answer 2

in muscle

Question 3

what is myoglobin made of in terms of helices

Answer 3

8 alpha helices

Question 4

Hemoglobin is what type of protein

Answer 4

tetrameric

Question 5

what groups does hemoglobin contain

Answer 5

4 heme groups

Question 6

Are the amino acid residues of the alpha and beta subunits identical?

Answer 6

No, not identical

Question 7

What is similar between the alpha and beta subunit

Answer 7

the 3D structure

Question 8

difference between myoglobin and hemoglobin in terms of polypeptide chain

Answer 8

Myo has single chain but hemo has mutiple

Question 9

does myo or heme bind easier to oxygen

Answer 9

Myo

Question 10

difference between myoglobin and hemoglobin in terms of ‘meric’

Answer 10

Myo is monomeric and hemo is tetrameric

Question 11

difference between myoglobin and hemoglobin in terms of how many oxygens can bind

Answer 11

Myo can bind one oxygen - monomer

hemo can bind 4 oxygens - tetramer

Question 12

The quaternary structure of hemoglobin features strong interactions between what

Answer 12

unlike subunits

Question 13

alpha1beta1 and alpha2beta2 interface involves how many residues and remains intact when what occurs

Answer 13

involves 30 residues

remains intact when the tetramer is disassembled with urea

Question 14

alpha1beta2 and alpha2beta1 interface involves how many residues and interactions are mostly what

Answer 14

involves 19 residues

mostly hydrophobic although there are many hydrogen bonds

Question 15

Mb and Hb fold into similar what

Answer 15

tertiary structures

Question 16

The backbone of mb and hb consists of what

Answer 16

8 alpha helices separated by bends

Question 17

side chains extend outward from the helices occupying what

Answer 17

nearly all the space between the folded loops

Question 18

what residues arent found on the outer surface and which ones are found in the interior

Answer 18

polar residues found on outer surface

hydrophobic residues in the interior

Question 19

The proline residues coincide with what

Answer 19

the loop regions

Question 20

the heme group is located within a pocket lined with what

Answer 20

hydrophobic amino acid side chains

Question 21

Heme is held in the hydrophobic pocket by coordinationof the iron with what

Answer 21

His93/F8

Question 22

On the other side of the heme, the iron is coordinated with what

Answer 22

a water molecule (deoxy form) or an oxygen molecule (oxy form)

Question 23

Another histidine, His64/HisE7 does what

Answer 23

helps hold the oxygen molecule in place

Question 24

how does oxygen bind to myglobin

Answer 24

reversibly

Question 25

For a monomeric protein such a myoglobin, the fraction of binding sites occupied a ligand is what

Answer 25

a hyperbolic function of ligand concentration

Question 26

Binding of oxygen to hemoglobin undrgoes what

Answer 26

a structural change

Question 27

what are the two major conformations of hemoglobin

Answer 27

R Relaxed and T Tense

Question 28

O2 has a significantly higher affinity for what

Answer 28

Hemoglobin in R state

Question 29

R state is also what

Answer 29

Oxyhemoglobin

Question 30

T state is also what

Answer 30

deoxyhemoglobin

Question 31

in the absence of o2 which state is more stable

Answer 31

T state

Question 32

The binding of O2 to hemoglobin subunit in the T state triggers a change in conformation to what state?

Answer 32

R state

Question 33

What happens in terms of structure during the transition between T and R state

Answer 33

when going from T to R, the alphabeta subunit slide past each other and rotate - narrowing of the pocket

Question 34

What happens to the ion pairs that stabilise the T state when going to R state

Answer 34

ion pairs are broken and new ones are formed

Question 35

what is the problem with having a protein with high affinity for o2 but is needed in 2 different places

Answer 35

A protein with high affinity for O2 in the lungs would not be able to release it in the tissue, and a protein with high affinity for O2 in the tissue would not bind much O2 in the lungs.
Different kPa’s

Question 36

How does hemoglobin solve the problem of O2 binding in areas of different kPa

Answer 36

Undergoes transition from low affinity state (T state) and a high affinity state (R State)

Question 37

Transition from two states resulted in hemoglobin having what shape

Answer 37

S shaped/ Sigmoid binding curve

Question 38

High affinity state is what

Answer 38

R state

Question 39

Which has the higher pKa? Tissues or Lungs

Answer 39

Lungs

Question 40

the binding of o2 to individual subunits can alter what

Answer 40

affinity for o2 in the next subunit

Question 41

why does the fourth o2 molecule binds easier to heme than the first one

Answer 41

heme already in R state and so binds with much higher affinity

Question 42

why is binding of o2 to hemoglobin an example of cooperative allosteric binding

Answer 42

binding of one ligand affects the remaining sites.
O2 can be considered as both a ligand and a homotropic modulator. There is only one O2 binding site per subunit, so the allosteric effect gives rise to cooperativity mediated by conformational changes transmitted from one subunit to another by subunit-subunit interactions.

Question 43

Why does hemoglobin function efficiently in oxygen transport

Answer 43

is a result of allosteric transition between high and low affinity states

Question 44

Allosteric changes in heme can also be promoted by what

Answer 44

Allosteric effectors - Carbon dioxide and protoons

Question 45

A decrease in pH lowers what for Hb

Answer 45

lowers the affinity for O2 binding