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H b
structure, function
© Department of Biochemistry (V.P.), Faculty of Medicine, MU Brno 2009
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Hb dospělých / adult Hb = HbA = a2 p2 Hb fetální     / fetal Hb = HbF = a2 y2
AA
14b AA
Mr = 64-.00O
(ntyoalobin   450AÁ)
High-spin Fe(II) (larger radius, lose 02)
^vysokosp'moyy stay*
ovy stay
faucet spim je yysoky} vet si'oojem Fe
Low-spin Fe(II) (smaller radius, gain 02)
M wzkospinovy stay
Iron in hem - remark
Iron is bonded to the cyclic tetrapyrrole so, that formal
two pyrrole nuclei lost H+ from their nitrogens.
This way free electrone pair was formed on every from two
nitrogens. The pair of electrons creates dative covalent bond with
Fe2+ (on every from two nuclei). Fe2+ brings in the molecule
of heme 2 positive charges, „lost" as 2 H+.
Heme in hemoglobin is now electric neutral and bonds also
electric neutral moleculs (O2, CO) too.
The oxidation of iron on Fe3+ (® hemiglobin, methemoglobin)
leads to gain of one positive charge in molecule of heme.
Then heme is a cation and bonds anionts (e.g. CN-, however it
is not able to bond electric neutral molecules - so it cannot
transfer oxygen).
The facts are important among others for toxicology.
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Bohrův efekt: snížení afinity kyslíku k Hb při nízkém pH Bohr effect :   decrease of affinity of oxygen to Hb at low pH
BPG = 2,3-bisphosphoglycerate
model: neúplně nafouknutý míč / model: not fully blow up ball 9
T-forma Hb (BPG) a R-forma Hb (O.) :
4 Oj*T
Deo
hemoglobin
BPG
stabilizes T-torm
C
it	1	
%		v
		
		OH*
		
BŤBC10TS
Hemoglobin; allosterfc effects
*" R (O^ + H1^ -h BPG
WÉHI		Iff _ J
- -i		
		1
		
		
[BPGJ+
tense [tens] napjatý release [ri'liis] uvolnění
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Vazba kyslíku na hemoglobin / saturační křivka (esovitá !) Oxygen binding to hemoglobin / saturation curve (sigmoidal!)
100
o 75
03 3
* Si
ď
50
25
0
I	1	1       1 1 4
	i	
X		
AJ		
	1	1        1 1
po.
kooperativní vazebná kinetika cooperative binding kinetics
li
saturace yfOO% -			
			
			
			
•	í		
smíšená venózní krev mixed venous blood jen 1 O2 z tetrameru ! / 1 O2 from tetramer only !			12
Conditions affecting the shift of dissociation curve :
Increased quantity of released oxygen	
by shift of the saturation curve to the right :	
s02	
	
	
	//
	/ / _.
	/ 1
	/ /
	/ /
	//
	
	As
	-p02
In the original position the curve allowes to release the quantum	
of oxygen comlaying with the blue line segment at the given pO2 .	
By the shift of the curve to the right is the quantum of accesible 14	
oxygen increased to the value given the red line segment.	
The expression of position of saturation curve :
s02
I         i ' !     1 "		P02(a)	-
""""""""""" ~t		P02(v)	
Jm	p50		-
-             / I			
I /    20 j A < • i 1 1 • I i 1 > i% —y, , . . I ,',    , 1', . ,'. , ,1	t r. I.11	0 60 80 1 1   1   I   1   1   1   1   1   1   M   1   1   1   M   II   1   1   M   1   1 1	mmHg -11111111
' 'I 'I I ' ' I I I ' ' ' Ifl ■    I I ' I I I I I I I II I I 11 I I I II I I I II I I 1 I I I , I I I I I I I I I I I I I I I I I ,
0       2       4       6       8       10      12 kPa
The position/shift of saturation curve is expressed parcial pressure of oxygen by 50 % saturation of Hb („the value p50"), it is the position of inflex point of the curve.
[ The normal value of p50 is ~ 3,25 kPa (2,9 - 3,6 kPa) ]
sO
PO;
saturační křivka saturation curve
cO2 (mmol / l)
PO
absorpční křivka absoption curve
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Transport of CO2 in blood :
1/ 85 % HCO3-
2/ 10 % carbamate (carbamino
compouds) 3/ 5 %   physically dissolved
(chemically not affected CO2)
Hb - NH2 + CO2    ®    Hb - NH - COOH
carbamic acid = aminoformic acid - COOH
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Transfer of CK, and CCK,
CO,
alveolar arterial blood
venous blood
Erc
IICO
-CO:
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karbonatdehydratasa
(karboanhydratasa)
( carbonic anhydrase, carbonate hydro-lyase EC 4.2.1.1 )
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p02 of arterial blood (aB-p02}_:
age	average	range
20 - 29	12,66 kPa	10,66 -14,66
30 - 39	12 kPa	10,4 -14,4
40 -49	11,46 kPa	10 -13,86
50 -59	10,93 kPa	9,46 -13,33
60 - 69	10,4 kPa	8,66 -12,66
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pO2 of arterial blood (aB-pO2)_:
aB-pO2 is decreased with increasing age
cB-pO2 values are approximately by 10-20 % lower
aB-pO2 values in lying patients are lower about 1,33 kPa in comparison with described
symbolic: a = arterial [ai'tiarial] B = blood [blad] c = capillary [ks'pilsri] p = partial pressure [pa:sl press] v = venous [vi:nss]
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Representation of constituent forms of Hb :
So called oxymeters measure at wavelength which are
absoption maxima:   ( - see next )
H Hb   = reduced hemoglobin
O2 Hb   = oxyhemoglobin
CO Hb = carbonylhemoglobin
Met Hb = methemoglobin
Sulf Hb= sulfhemoglobin
From the concentration of the whole Hb are subtracted all forms of Hb, which are not able to transfer oxygen ( CO Hb + Met Hb + Sulf Hb ).
The sum ( O2Hb + H Hb ) is then Hb utilizable for transfer of oxygen = „active (effective) Hb"
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Molar Absorpivity (Extinction Coefficient) (mmol/L) 1 cm 1
c 535    560 577 622 636 670
0 ' — HHb
Wavelength
Hb dospělých / adult Hb = HbA = a2 p2 Hbfetální     / fetal Hb = HbF = a2y2
100 r
80 ■
60
40
20 "
0
a • chain
0 3 6
Gestation in months
Birth      3 6 Age in months
E.R. Huehns et al
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Air composition (1) :
	volume %
O2	20,9
CO2	0,03
N2	78,1
inert gases	0,9
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Air composition (2) :
	inspired	expired
pO2	21 kPa	15,33 kPa
pCO2	0,03 kPa	4,4 kPa
p(N2 + inert gases)	79,4 kPa	75,33 kPa
pH2O	0,76 kPa	6,27 kPa
The sum of partial pressures is 101,3 kPa in both cases. Expired air is fully saturated with water vapour (data pH2O for alveoli and 37°C).
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