Transport of oxygen in the blood

Question 1

two forms oxygen is present in in the blood

Answer 1

dissolved in plasma and erythrocyte cytosol

reversibly combined w/ hemoglobin molecules in erythrocytes

Question 2

1 litre blood and oxygen

oxygen carried to tissues

Answer 2

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

Question 3

henry’s law

Answer 3

amount of oxygen dissolved in blood is directly proportional to Po2 of blood

Question 4

solubility of oxygen

Answer 4

low solubility in water

Question 5

hemoglobin

Answer 5

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

Question 6

two forms of hemoglobin

Answer 6

deoxyhemoglobin (Hb)

oxyhemoglobin (HbO2)

Question 7

percent hemoglobin saturation

Answer 7

O2 bound to Hb / maximal capacity of Hb to bind O2

x 100

Question 8

factors affecting total amount of oxygen carried by hemoglobin

Answer 8

% saturation of hemoglobin
how much hemoglobin is in each litre of blood
anemia

Question 9

factor affecting hemoglobin content in the blood

Answer 9

low hematocrit - chronic blood loss or dietary deficiencies affecting erythrocyte production

Question 10

effect of blood PO2 on hemoglobin saturation

Answer 10

increases it

Question 11

what are globin units held by?

Answer 11

globin units of deoxyhemoglobin are tightly held by electrostatic bonds in conformation with low affinity for oxygen

Question 12

binding of oxygen to heme molecule

Answer 12

breaks some of the electrostatic bonds between globin units, so oxygen binding sites are more exposed and the affinity is increased

Question 13

shape of oxygen-hemoglobin dissociation curve

Answer 13

steep slope between 10 and 60mmHg (increase in hemoglobin saturation) and plateau between 70 and 100mmHg (small increase)

Question 14

importance of plateau

Answer 14

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)

Question 15

steep portion of curve

Answer 15

ideal for unloading oxygen in tissues

Question 16

what contributes to pO2 of blood?

Answer 16

dissolved oxygen, not oxygen bound to hemoglobin

Question 17

hemoglobin affect on pO2

Answer 17

decreases

Question 18

why is the interstitial fluid pO2 always more than that in cells

Answer 18

mitochondria in cells are using up oxygen

Question 19

why is the interstitial fluid pO2 always less than that in capillaries?

Answer 19

oxygen rapidly diffusing into cells

Question 20

effect of oxygen diffusion on plasma pO2

Answer 20

becomes lower than erythrocyte pO2 - diffuses out into plasma - dissociation of oxygen from hemoglobin

Question 21

hemoglobin saturation in resting tissues

Answer 21

75% - cells can obtain more oxygen when they increase their activity

Question 22

effects of carbon monoxide on hemoglobin

Answer 22

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

Question 23

factors affecting hemoglobin saturation

Answer 23

blood pO2, H+ conc, temp, conc of 2,3-diphosphoglycerate, fetal hemoglobin

Question 24

effects of factors affecting hemoglobin saturation

Answer 24

increased DPG conc, temp and acidity causes dissociation curve to shift to the right

Question 25

effects of increased Pco2, H+ conc and temp

Answer 25

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

Question 26

effects of fetal hemoglobin on hemoglobin saturation

Answer 26

shifts curve to left

has greater affinity for oxygen, allowing oxygen content from oxygen diffusion from maternal to fetal blood in placenta

Question 27

effects of metabolic activity on Pco2, H+conc, temp

Answer 27

increased metabolic activity increases it

Question 28

allosteric modulation of hemoglobin and temp’s effect

Answer 28

co2 and H+ bind to globin portion, and alter conformation.

temp reduces affinity for o2

Question 29

DPG

Answer 29

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

Question 30

fetal hemoglobin

Answer 30

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