Haemoglobin and Myoglobin

Question 1

Myoglobin primary

Answer 1

~150 a.a

Question 2

Myoglobin secondary

Answer 2

8 ⍺-helices

Question 3

Myoglobin tertiary

Answer 3

Fold with hydrophobic pocket (Val E11 & Phe CD1)

Haem binds to HisF8

Question 4

Hydrophobic pocket prevents

Answer 4

Oxidation to Fe3+

Question 5

Haem

Answer 5

Cofactor

Fe2+ (reversible)

Question 6

Myoglobin quad

Answer 6

Monomeric

Question 7

Haemoglobin structure

Answer 7

Tetramer
4 goblin proteins non - covalently
1 haem - binds 1 O2

Question 8

M O2 release

Answer 8

Low O2
HisE7, oppo haem
Distorts O2 binding
Easier to release, lower affinity

Question 9

M storage

Answer 9

In muscle

Question 10

M curve

Answer 10

Hypobolic curve

Saturated at low O2 until too low, all released (steep drop)

Question 11

H T and R state shape

Answer 11

T - dished haem
R - O2 flattens haem, pulls HisF8 and helix F to binding site, increase O2 binding
Anything that pulls helix F away = weakens oxygen binding

Question 12

T / R stablisation

Answer 12

Steric and polar interactions

Question 13

H curve

Answer 13

Sigmoidal curve
Bind in lungs (high partial pressure ~100 Torr)
Release in peripheral tissue (low partial pressure ~20 Torr)

Question 14

Absorbance eq

Answer 14

log(I𝗼/I)

Question 15

Beer - Lambert Law

Answer 15

A = EcL

Question 16

E unit

Answer 16

Lmol-1cm-1

Question 17

Beer’s

Answer 17

Decrease in intensity of transmitted light as conc increase

Question 18

Lambert’s

Answer 18

Decrease in transmitted light as pathlength increases

Question 19

Standard curve

Answer 19

Pass orgin

No greater than 1.0 (dilute if needed)

Question 20

H cooperativity

Answer 20

Influences to be either R or T, all in same state

Question 21

MWC model

Answer 21

Only explains positive cooperativity (increase affinity, shift to T doesn’t decrease affinity)
Each bind shifts equilibrium to R

Question 22

KNF model

Answer 22

Negative copperativity (T state influences others, easier release)
T -> R influences neighbouring subunits = easier to bind O2

Question 23

T

Answer 23

Low affinity - hard binding

Question 24

R

Answer 24

High affinity - easy binding

Question 25

BPG what is it?

Answer 25

Allosteric inhibitor
Binds to deoxy-Hb by electrostatic interactions
Produced in peripheral tissue

Question 26

BPG effects

Answer 26

Stablises T state, decrease O2 affinity

Rightward shift

Question 27

CO2 effects

Answer 27

Decrease O2 affinity by decreasing pH (N terminal H+ protonate a.a side chains)
Stabilise T-state

Question 28

Feoetuses alternate isoforms

Answer 28

𝜻 = ⍺

𝛜 & γ = β

Question 29

alternate isoforms why?

Answer 29

Higher affinity

Question 30

Feoetuse benefit

Answer 30

Lack a.a that binds BPG

Question 31

Methaemoglobin

Answer 31

Fe2+ -> Fe3+ O2 doesn’t bound

Shifts subunit into R state, doesn’t release O2 bound

Question 32

Boston haemoglobin

Answer 32

HisE7 -> TyrE7
= Fe3+
Breaks Fe - HisF8 = Remains T state

Question 33

HbS

Answer 33

“Gain in function”
β6 Glu -> Val (abnormal hydrophobic interaction)
Polymerisation = distort RBC

Question 34

Allosteric control

Answer 34

Lactate

Decrease O2 affinity, doesn’t bind to where oxygen binds

Question 35

Bohr Effect

Answer 35

Increase CO2 and decrease pH
Reduce binding affinity

CO2 - bind to N - terminal
H+ - also protonate ionisable side chains
Stabilise deoxy - Hb