Final: Lecture 25 Flashcards
Diffusing capacity of oxygen increases ____ during exercise.
- 3x
- Increased surface area of capillaries participating in diffusion
- There is a more nearly ideal Va/Q ratio in the upper parts of the lungs
Hemoglobin
- Tetrameric structure made up of 4 globins
- Each globin attached to protoporphyrin (heme) group
- Each heme group has ferrous group (Fe++) at its center
- Each (Fe++) can bind 1 molecule (diatomic) of oxygen
Factors that determine tissue PO2:
- Rate of oxygen transport to the tissues
* Rate of oxygen consumption by the tissues
Normal intracellular mean PO2 is?
- **23 mm Hg
- Normal range = 5-40 mm Hg
- 1-3 mm Hg PO2 required for normal cellular respiration
Normal intracellular PCO2 is?
- 46 mm Hg (compared to interstitial of 45)
- Arterial blood entering tissues = 40 mm Hg
- Venous blood leaving tissues = 45 mm Hg
Alveolus PO2 is?
•104 mm Hg*
PO2 at the arterial end of capillary is?
- 95 mm Hg
* Not 104 because of mixture with pulmonary shunt blood
PO2 at venous end of capillary is?
- 40 mm Hg
* Same as interstitial fluid PO2
PCO2 at arterial end of capillary is?
•40 mm Hg
Intracellular PCO2 is?
- 46 mm Hg
* Interstitial fluid PCO2 is 45 mm Hg, so CO2 wants to leave cells
PCO2 at venous end of capillary is?
- 45 mm Hg
* Same as interstitial fluid
10 x normal metabolism will do what to interstitial PCO2?
- Increase from 45 mm Hg to roughly 60 mm Hg
* 1/4 normal metabolism lowers just a little
4 x normal O2 consumption does what to interstitial PO2?
- Lowers from 40 mm Hg to about 20 mm Hg
* 1/4 normal O2 consumption raises to about 60 mm Hg
Venous blood PO2 is 40 mm Hg, what is the O2 saturation?
- 75%
* This means that oxygen is bound to 3/4 of the heme groups
Arterial blood PO2 is 95 mm Hg, what is the O2 saturation?
- 97%
* This means that oxygen is bound to 97% of the heme groups
1 gram of Hb can bind to ____ ml O2.
•1.34
1 dl blood carries ___ ml O2.
•20.1
Utilization coefficient
- Percentage of blood that give up its oxygen
- 5/19.4 = 25%
- Strenuous exercise –> 75-85%
Hemoglobin as a “Tissue Oxygen Buffer” System
•In order to release 5 ml of oxygen/dl of blood at rest*: PO2 must fall to about 40 mm Hg, tissue PO2 cannot rise above this level
When PO2 is high (pulmonary capillaries), oxygen _______ with hemoglobin.
•Binds
When PO2 is low (tissue capillaries) oxygen _________ from hemoglobin.
•Is released
When exercising, transported O2 to tissues raises from 5 ml/dl to?
•15 ml O2/dl*
Oxygen-hemoglobin curve shift to the right caused by:
- Decrease in pH
- Shift to the right; Increased H+ ions, CO2, temperature, and BPG
- Normal BPG keeps dissociation curve slightly shifter to the right
Bohr Effect
- Increase in blood (CO2) and H+ ions: shifts curve to right, enhances release of O2 from the blood in tissues, enhances oxygenation of blood in lungs
- Decrease in blood (CO2) and H+ ions: shifts curve left, occurs in lungs (hemoglobin picks up more oxygen)
When cellular PO2 is more than 1 mm Hg, _____ becomes the limiting factor in the rates of chemical change.
•ADP
Carbon Dioxide Transport
- Small amount is dissolved in the blood: 2.7 ml/dl at 45 mm Hg, 2.4 ml/dl at 40 mm Hg (accounts for about 7% of CO2 transport)
- About 70% is transported as carbonic acid: requires carbonic anhydrase, also employs bicarbonate/Cl transporter
- Remember transported as carbamino hemoglobin
Bohr vs. Haldane Effects
- Bohr: increase blood CO2 causes O2 to be displaced from hemoglobin, shifts curve right
- Haldane: binding of O2 with hemoglobin (makes it a stronger acid) displaces CO2 from blood, more acidic hemoglobin less tendency to bind with CO2, increase acidity causes it to release H+ ions
Carbon Monoxide Transport
- Displaces oxygen on the hemoglobin molecule
- Binds 250x stronger than oxygen
- Poisoning, O2 content of blood greatly reduced, but PO2 may be normal
- Therefore: blood may be BRIGHT RED**
