Blood/Gas Transport Flashcards
(20 cards)
Oxygen content of systemic arterial blood at sea level, dissolved and hemoglobin-bound
1 Liter of arterial blood contains
1.5% dissolved O2
98.5% hemoglobin-bound O2
Hemoglobin structure
- Globin, composed of 4 polypeptide chains
- Heme, contains Fe that binds O2
One Hb has the potential to bind 4 O2 molecules
Fetal Hb
α2γ2, has a higher affinity for O2 than adult to facilitate movement of O2 from the mother to the fetus.
HbS, sickle cell anemia
Abnormal variant of β subunit that causes SCD. When deoxygenated, HbS forms sickle-shaped rods in rbcs, resulting in occlusion of small blood vessels.
Also have a lower O2 affinity.
O2-Hemoglobin dissociation curve
% Hb saturation is a function of the O2Hb dissociation curve. Results from the positive co-operativity of O2 in binding to Hb.
Sigmoidal in shape with steep increase as PO2 goes from 0-40%, levelling off at 60mmHg and above.
P50, changes
P50 = Po2 at which Hb is 50%
Changes in P50 inversely reflect changes in affinity for O2, eg. increasing P50 indicates a decreased affinity for O2.
Bohr effect
Right shift
Increase CO2 production decreases pH and decreases Hb-O2 affinity. This promotes the release of O2 to the tissues.
Increase in temp, PCO2, and 2,3-DPG, decrease in pH.
Haldane effect
As blood passes through the lungs, CO2 is exhaled and pH increases, shifting the curve to the left.
Increased O2 affinity promotes uptake.
Decrease in temp, PC2, and 2,3-DPG, increase in pH.
Caron monoxide poisoning mechanism
Decreases the O2 bound to Hb, prevents binding but increases the affinity, shifting the O2-Hb curve left. Co preferentially binds Hb 250x, normal 1% but increase to 10% bound if smoker, near traffic pollution.
Hypoxia
Region is deprived of an adequate supply of O2
Hypoxemia
Abnormally low levels of O2 in arterial blood
Hypoxic hypoxia
Most common. Decrease in PaO2 and decrease in delivery of O2 to tissues. Caused by pulmonary diseases such as COPD and fibrosis.
Circulatory hypoxia
Reduced blood flow to organ, usually due to vascular disease.
Anemic hypoxia
Inability of blood to carry sufficient O2, from low Hb or inability of Hb to carry O2 (HbCO).
Histotoxic hypoxia
Blocks ETC in mitochondria and thus prevents the utilisation of O2 by the cell, caused by poisons such as cyanide.
Dissolved CO2
About 20x more soluble than O2 and plays a greater role in gas transport, about 10%.
Carbamino compounds
Formed by the combination of Co2 with terminal amino groups in blood proteins (20-30%)
Bicarbonate
MOST (60%)
Catalysed by carbonic a hydrate in RBCs.
When HCO3- rises in erythrocytes, transported out in exchange for Cl- (chloride shift). Cell membrane is relatively impermeable to H+. Some binds to Hb.
Respiratory acidosis
Caused by hypoventilation or lung disease that prevent the normal elimination of CO2.
Respiratory alkalosis
Caused by hyperventilation.
