Biomedical Engineering Reference
In-Depth Information
Adult human RBCs mostly express I antigens and contain only a few i antigens,
whereas the latter predominates in fetal and neonatal erythrocytes. After birth, the
quantity of I antigens gradually rises and the amount of i antigens falls; adult values
are reached about at month 18.
The
Raph
blood group antigen dovetails with transmembrane glycoprotein GP27,
a.k.a. platelet-endothelial tetraspan antigen PETA3, CD151, and tetraspanin-24.
The
Scianna
(Sc)
blood
group
is
determined
by
erythroblast
membrane
-associated protein (ERMAP) that is encoded by the Ermap gene.
The
Landsteiner-Wiener
(LW) blood group has been renamed intercellular
adhesion molecule ICAM4.
The
Lutheran
(Lu) blood group with antigens LuA and LuB is based on genes
on chromosome 19.
P blood group
components (Pl) are encoded by genes on chromosome 22.
The
XG blood group
is encoded by the PBDX gene on X chromosome.
Other blood group antigens include globoside, a glycosphingolipid also named
erythrocyte P antigen, and Rh-associated glycoprotein, a putative gas channel
protein.
3.5.7
Hemoglobin Solution in Erythrocytic Capsule
10
6
Each RBC contains about 280
×
hemoglobin molecules [
134
]. Hb consists
. It contains four iron atom Fe
2
+
, in the center
of hemes.
35
Hemoglobin carries oxygen (O
2
) from lungs to tissues and help to
transport carbon dioxide (CO
2
) from tissues to lungs.
36
Hemoglobin is also involved
in pH regulation.
of four globin chains
α
and
β
35
Heme is a component of several hemoproteins that is required for: (1) oxygen transport
and storage (hemoglobin and myoglobin); (2) electron transfer (cytochromes); and (3) signal
transduction (nitric oxide synthases).
36
One O
2
molecule can reversibly bind to each heme to form oxyhemoglobin. The reaction is
reversible because O
2
is taken when its concentration ([O
2
]) is high and released when [O
2
]islow.
O
2
combination to and release from Fe
2
+
is accelerated by already existing O
2
-Fe
2
+
interactions.
Under conditions of lower temperature, higher pH, and increased O
2
partial pressure (
p
O
2
), O
2
fixes to Hb. When temperature is higher, or when pH and O
2
partial pressure lower, the reverse
reaction is promoted. With alveolar values of
p
A
O
2
=
3 kPa, the arterial
and mixed venous blood values are
p
a
O
2
=
12
.
7kPa,
p
a
CO
2
=
5
.
1-5.3 kPa,
p
v
O
2
=
4
.
9kPa, and
p
v
CO
2
13
.
7kPa and
p
A
CO
2
=
5
.
9-6.1 kPa. About 95% of CO
2
generated by cells is carried in RBCs and about 5%
dissolves in plasma. A part of CO
2
is bound to hemoglobin (carbaminohemoglobin). The rest is
converted by carbonic anhydrase contained in RBCs into bicarbonate ions (HCO
3
) and hydrogen
ions (H
+
), which bind to the hemoglobin and do not affect pH
=
5
.
H
+
+
HCO
3
.
CO
2
+
H
2
O
⇔
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