Respiratory Physiology Flashcards
respiratory pigments
- oxygen transport pigments
- serve to bind O2 at respiratory surface and transport it through blood to tissues, and to remove CO2
- some also used as storage (ex: myoglobin in tissues)
- reversible combination with oxygen (pick up O2 at lungs, release at tissue)
inc the amount of O2 that can be carried by unit volume of blood
facultative diffusion
accepts O2 from hemoglobin and stores it in tissues until muscle need it
hemoglobin
- acid-base buffers
- participate in blood CO2 transport and O2 transport
- each contains 4 iron porphyrin prosthetic groups (hemes)
- contains 2 copies of alpha globin and 2 copies of beta globin
- each 4 polypeptide chains contain a heme molecule which is site for O2 binding
heme
associated non-covalently with protein globulin
- each heme binds 1 oxygen (4 hemes)
- 4 units=4 O2 molecules
globins
- proteinaceous
- subunits are different
human fetal hemoglobin
gamma and epsilon chains
oxygenated
hemoglobin combined with O2
deoxygenated
hemoglobin released O2
differences in Hb are due to differences in…
- amino acids in proteins
- alpha globin genes from chromosome 16
- beta and fetal genes from chromosome 11
where is hemoglobin found?
inside RBC (except with some insects)
myoglobin
- muscle hemoglobin
- 1 heme
- concentrated in muscle (cytoplasm of muscle fibers)
- hemoglobin unloads oxygen to myoglobin
- myoglobin has greater oxygen affinity than hemoglobin
chlorocruorin
- “green hemoglobin”
- 80 hemes per molecule
- green, found in 4 families marine annelids
- free floating, not specialized cells (dissolved in blood plasma)
- contains Fe and heme
- binds 1 O2 molecule per heme
hemerythrin
- 8 subunits
- no heme
- contain Fe directly to protein (each O2 binding site has 2 iron atoms)
- found in polychaetas
- sound in blood cells
hemocyanin
- copper containing pigment bound directly to protein (each O2 binding site has 2 copper atoms– 1 O2 per 2 Cu)
- no heme, no iron
- blue with oxygen
- high mw keeps down osmolarity
- not found in blood cells
- found in non-insect arthropods
- reverse Bohr effect (dec pH-> inc affinity)
never in muscle/solid tissue)
cytochromes
- have heme structure
- involved in electron transport and oxidative phosphorylation in mitochondria
Affinity for Oxygen
- affinity= how readily combine with O2
- respiratory pigments combine reversibly with oxygen over a range of partial pressures of O2
- thus serving as O2 carriers by loading at the respiratory surface and unloading at the tissues
saturated
O2 partial pressure is high enough for all O2 binding sites to be oxygenated
% saturation
percentage of binding sites that are oxygenated
Hb-O2 saturation curve
shows the relation between the percentage of binding sites that are oxygenated and the O2 partial pressure
P50
- when Hb is 50% saturated
- partial pressure of O2 at 50% saturation of hemoglobin
- measure of affinity of a particular Hb for O2
as P50 inc-> affinity dec
low affinity
pigments that need high O2 partial pressure for full loading and unload substantial amounts of O2 at high partial pressures
high affinity
pigments that load fully at low partial pressure and require low partial pressure for unloading
a shift to the right means…
O2 affinity
the O2 partial pressure needed to saturate is higher and the P50 is higher, thus… O2 affinity is lower
(lowering O2 affinity shifts to the right, raising affinity shifts to the left)
When hemoglobin molecule binds 1 O2…
this increases affinity of the molecule to bind more O2
- if 4 hemes bind O2 = 100% saturated
- the affinity of Hb must be turned to specific needs of the organism (ie: animals need to bind Hb at the lungs and unload it at the tissues; partial pressure of O2 differs at these two sites)