Transport of oxygen in the blood Flashcards
two forms oxygen is present in in the blood
dissolved in plasma and erythrocyte cytosol
reversibly combined w/ hemoglobin molecules in erythrocytes
1 litre blood and oxygen
oxygen carried to tissues
3ml o2 physically dissolved (1.5%)
197ml o2 bound to hemoglobin (98.5%)
cardiac output = 5L/min
o2 carried to tissues = 5 x 200 = 1000mL o2/min
henry’s law
amount of oxygen dissolved in blood is directly proportional to Po2 of blood
solubility of oxygen
low solubility in water
hemoglobin
protein
4 subunits bound together
subunit: heme and polypeptide attached to the heme
globin: 4 polypeptides in molecule
molecular oxygen binds to Fe in heme group
single hemoglobin can bind 4 oxygens
two forms of hemoglobin
deoxyhemoglobin (Hb)
oxyhemoglobin (HbO2)
percent hemoglobin saturation
O2 bound to Hb / maximal capacity of Hb to bind O2
x 100
factors affecting total amount of oxygen carried by hemoglobin
% saturation of hemoglobin
how much hemoglobin is in each litre of blood
anemia
factor affecting hemoglobin content in the blood
low hematocrit - chronic blood loss or dietary deficiencies affecting erythrocyte production
effect of blood PO2 on hemoglobin saturation
increases it
what are globin units held by?
globin units of deoxyhemoglobin are tightly held by electrostatic bonds in conformation with low affinity for oxygen
binding of oxygen to heme molecule
breaks some of the electrostatic bonds between globin units, so oxygen binding sites are more exposed and the affinity is increased
shape of oxygen-hemoglobin dissociation curve
steep slope between 10 and 60mmHg (increase in hemoglobin saturation) and plateau between 70 and 100mmHg (small increase)
importance of plateau
high altitude and pulmonary disease - moderate reduction in alveolar and arterial pO2
even if decreased to 60mmHg, hemoglobin saturation is still at 90%
increasing alveolar pO2 by hyperventilation or breathing 100% o2 doesn’t increase blood o2 much (only applies to healthy people - would help unhealthy people)
steep portion of curve
ideal for unloading oxygen in tissues
what contributes to pO2 of blood?
dissolved oxygen, not oxygen bound to hemoglobin
hemoglobin affect on pO2
decreases
why is the interstitial fluid pO2 always more than that in cells
mitochondria in cells are using up oxygen
why is the interstitial fluid pO2 always less than that in capillaries?
oxygen rapidly diffusing into cells
effect of oxygen diffusion on plasma pO2
becomes lower than erythrocyte pO2 - diffuses out into plasma - dissociation of oxygen from hemoglobin
hemoglobin saturation in resting tissues
75% - cells can obtain more oxygen when they increase their activity
effects of carbon monoxide on hemoglobin
carbon monoxide has an affinity for the oxygen-binding sites on hemoglobin 210 x that of oxygen
reduces amount of oxygen binding by competition
deleterous effect: decreases unloading of oxygen into tissues
factors affecting hemoglobin saturation
blood pO2, H+ conc, temp, conc of 2,3-diphosphoglycerate, fetal hemoglobin
effects of factors affecting hemoglobin saturation
increased DPG conc, temp and acidity causes dissociation curve to shift to the right
effects of increased Pco2, H+ conc and temp
continuously exerted on blood in tissue capillaries, as they’re greater in tissue capillary blood than arterial blood
Pco2 increased due to co2 entering blood from tissues
H+ increased due to elevated Pco2 and release of metabolically produced acids, e.g. lactic acid
temp increased due to heat produced from tissue metabolism
hemoglobin passing through these has less affinity for oxygen, so it gives it up
effects of fetal hemoglobin on hemoglobin saturation
shifts curve to left
has greater affinity for oxygen, allowing oxygen content from oxygen diffusion from maternal to fetal blood in placenta
effects of metabolic activity on Pco2, H+conc, temp
increased metabolic activity increases it
allosteric modulation of hemoglobin and temp’s effect
co2 and H+ bind to globin portion, and alter conformation.
temp reduces affinity for o2
DPG
produced during glycolysis
reversibly combines with hemoglobin, allosterically causing it to have lower affinity for oxygen
erythrocytes have large amounts of DPG due to them having no mitochondria and relying on glycolysis
important in high altitudes
fetal hemoglobin
contains subunits coded for by different genes to those expressed postnatally
alter shape of final protein
higher affinity for oxygen
lower arterial Po2
increased oxygen uptake across placental diffusion barrier to supply development
