Transcript Carriage of respiratory Gases

Carriage of respiratory
Gases
By
Y Stock
Objectives
 You
should be able to:
 Describe the structure of
erythrocytes.
 Describe the role of respiratory
pigments.
 Understand
curves.
and interpret dissociation
WWW.NIM.NIH.GOV
Red blood cells
 Biconcave
discs
 8 micrometers diameter
 No
nucleus
 Made
in bone marrow
 Destroyed by liver/spleen
Function: To carry oxygen and
carbon dioxide
 Adaptions:
 Shape
gives a large surface area,
encouraging diffusion
 Full
of haemoglobin
www.astrographics.com/.../Display/GP2120.jpg
Haemoglobin

www.chemsoc.org/.../LearnNet/cfb/images/13A.jpg
Haemoglobin
 Consists
of 4 polypeptide chains,
each with an iron containing haem
group.
 Each
haem group combines with an
oxygen molecule
Haemoglobin+oxygen=oxyhaemoglobin
Hb
+ 4O2 = HbO8
Reversible
reaction
www.scientific-art.com/.../Haemoglobin.gif
Hb + 4O2 = HbO8



High partial
pressure oxygen
Lungs
Oxyhaemoglobin
formed




Low partial
pressure oxygen
Active tissues
Oxyhaemoglobin
breaks down
Oxygen released
Oxygen dissociation curves
 Found
by exposing haemoglobin to
air mixtures of varying oxygen partial
pressures and determining its %
saturation.
www.jcu.edu/biology/RESPS.JPG
S shaped curve
 Over
the steep section a small fall in
Oxygen partial pressure causes a
sizeable drop in % saturation.
The curve shows that:


at relatively low oxygen concentrations
there is uncombined haemoglobin in the
blood and little or no oxyhaemoglobin,
e.g. in body tissue
at relatively high oxygen concentrations
there is little or no uncombined
haemoglobin in the blood; it is in the form
of oxyhaemoglobin, e.g. in the lungs.
Effect of increased carbon dioxide
Bohr Effect
 Curve
shifted to right
 Increased
CO2 causes
oxyhaemoglobin to unload some of
its oxygen.
www.coheadquarters.com/Bohr1.gif
Fate of carbon dioxide
 7-10%
dissolves in plasma
 20-30%
in red cells as
carbaminohaemoglobin (binds to
amino acids)
 60-70%
plasma
converted to bicarbonate in
Conversion to bicarbonate
 Carbon
dioxide diffuses into red cells
 Enzyme:carbonic
 CO2
anhydrase
+ H2O = H2CO3
This dissociates

H2CO3 = H+ + HCO3-

HCO3- diffuses into plasma
H+ combine with oxyhaemoglobin forming
haemoglobinic acid.
 H+ + HbO2 = HHB + O2

Oxygen displaced.
 Haemoglobin buffering pH changes

www.colprado.edu/.../image/figure13g.jpg
Myoglobin -Curve shifted to left
 Myoglobin
oxygen.
 Oxygen
PO2
binds more tightly to
only given up at very low
Images.encarta,msn.com/…/cha/00076b5f.gif
Quiz
Haemoglobin quiz image search RSC