resp 7

Question 1

how does plasma O2 determined?

Answer 1

by alveolar PO2 which depends on:
-composition of inspired air
-alveolar ventilation rate
-efficiency of gas exchange

Question 2

the amount of oxygen bound to hemoglobin depends on:

Answer 2

Question 3

how is oxygen binding expressed as a percentage?

Answer 3

-the amount of O2 bound to hb at any given PO2 is expressed as the percent saturation of hb
-active cells can have a lower PO2, for example, active muscles may have a PO2 as low as 2mmHG resulting in a larger release of O2

Question 4

what are the physical factors that alter hb’s affinity for O2?

Answer 4

-pH
-PCO2
-temperature
-2,3 BPG

Question 5

what would cause a decreasing shift in pH?

Answer 5

-maximal exertion produces excess CO2 ad pushes a cell into anaerobic metabolism. results in increased H+ and lactic acid in the cytoplasm and extracellular space
-shift in hb saturation as a result of pH or CO2 change: Bohr effect

Question 6

what is the effect of PCO2 on hb affinity?

Answer 6

increased aerobic metabolism results in increased CO2 production, this increases the PCO2 in the blood which:
1. readily binds Hb altering conformation
2. CO2 is readily converted to acid

Question 7

what is the effect of temperature on hb’s affinity?

Answer 7

-active muscles produce heat
-increased heat causes a conformational change in Hb leading to decreased affinity and more O2 to be dropped at the very active muscles

Question 8

what is the effect of 2,3 BFG on Hb’s affinity?

Answer 8

-a by-product of glycolysis in RBC’s
-chronic hypoxia increases 2,3 DPG production (RBC’s release ATP during hypoxia)
-ascent to higher altitude (low atmospheric PO2) and anemia can increase 2,3 BFG production

Question 9

what is the difference between adult hemoglobin and fetal hemoglobin?

Answer 9

Question 10

why does fetal hb have a higher affinity?

Answer 10

Question 11

what is the overview of the total oxygen content of arterial blood?

Answer 11

Question 12

what is the importance of removing CO2 from the body?

Answer 12

-elevated PCO2 causes acidosis, low pH leads to interruptions in hydrogen bonds and denaturing of proteins
-abnormally high PCO2 depresses the CNS causing confusion, coma, or even death

Question 13

what are the ways that CO2 is transported?

Answer 13

1. although very soluble in liquids, cells produce far more CO2 than plasma is capable of carrying
   -only about 7% of CO2 carried by venous blood is dissolved in plasma
2. remaining 93% diffuses into RBCs
   -23% binds to hemoglobin HbCO2 (caraminohemoglobin)
   -70% is converted into HCO3- (bicarbonate)

Question 14

what is the graph of how CO2 in blood is converted into a bicarbonate ion?

Answer 14

Question 15

the conversion of CO2 to HCO3- serves two purposes:

Answer 15

1. provides an additional means of CO2 transport from cells to the lungs
2. HCO3- is available to act as a buffer for metabolic acids, stabilizing body’s pH

Question 16

hb acts as a buffer and binds excess H+ ions:

Answer 16

-prevents large change in the body’s pH
-if blood CO2 is elevated too high Hb cannot soak up all the H+ and respiratory acidosis can result

Question 17

conversion of CO2 to HCO3- and H+ continues until _______________

Answer 17

EQUILIBRIUM IS REACHED
-to ensure equilibrium is not reached, two mechanisms exist: one to remove HCO3- from RBC and another to mop up excess H+