Final: Lecture 25

Question 0

Diffusing capacity of oxygen increases ____ during exercise.

Answer 0

• 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

Question 1

Hemoglobin

Answer 1

• 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

Question 2

Factors that determine tissue PO2:

Answer 2

• Rate of oxygen transport to the tissues

* Rate of oxygen consumption by the tissues

Question 3

Normal intracellular mean PO2 is?

Answer 3

• **23 mm Hg
• Normal range = 5-40 mm Hg
• 1-3 mm Hg PO2 required for normal cellular respiration

Question 4

Normal intracellular PCO2 is?

Answer 4

• 46 mm Hg (compared to interstitial of 45)
• Arterial blood entering tissues = 40 mm Hg
• Venous blood leaving tissues = 45 mm Hg

Question 5

Alveolus PO2 is?

Answer 5

•104 mm Hg*

Question 6

PO2 at the arterial end of capillary is?

Answer 6

• 95 mm Hg

* Not 104 because of mixture with pulmonary shunt blood

Question 7

PO2 at venous end of capillary is?

Answer 7

• 40 mm Hg

* Same as interstitial fluid PO2

Question 8

PCO2 at arterial end of capillary is?

Answer 8

•40 mm Hg

Question 9

Intracellular PCO2 is?

Answer 9

• 46 mm Hg

* Interstitial fluid PCO2 is 45 mm Hg, so CO2 wants to leave cells

Question 10

PCO2 at venous end of capillary is?

Answer 10

• 45 mm Hg

* Same as interstitial fluid

Question 11

10 x normal metabolism will do what to interstitial PCO2?

Answer 11

• Increase from 45 mm Hg to roughly 60 mm Hg

* 1/4 normal metabolism lowers just a little

Question 12

4 x normal O2 consumption does what to interstitial PO2?

Answer 12

• Lowers from 40 mm Hg to about 20 mm Hg

* 1/4 normal O2 consumption raises to about 60 mm Hg

Question 13

Venous blood PO2 is 40 mm Hg, what is the O2 saturation?

Answer 13

• 75%

* This means that oxygen is bound to 3/4 of the heme groups

Question 14

Arterial blood PO2 is 95 mm Hg, what is the O2 saturation?

Answer 14

• 97%

* This means that oxygen is bound to 97% of the heme groups

Question 15

1 gram of Hb can bind to ____ ml O2.

Answer 15

•1.34

Question 16

1 dl blood carries ___ ml O2.

Answer 16

•20.1

Question 17

Utilization coefficient

Answer 17

• Percentage of blood that give up its oxygen
• 5/19.4 = 25%
• Strenuous exercise –> 75-85%

Question 18

Hemoglobin as a “Tissue Oxygen Buffer” System

Answer 18

•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

Question 19

When PO2 is high (pulmonary capillaries), oxygen _______ with hemoglobin.

Answer 19

•Binds

Question 20

When PO2 is low (tissue capillaries) oxygen _________ from hemoglobin.

Answer 20

•Is released

Question 21

When exercising, transported O2 to tissues raises from 5 ml/dl to?

Answer 21

•15 ml O2/dl*

Question 22

Oxygen-hemoglobin curve shift to the right caused by:

Answer 22

• Decrease in pH
• Shift to the right; Increased H+ ions, CO2, temperature, and BPG
• Normal BPG keeps dissociation curve slightly shifter to the right

Question 23

Bohr Effect

Answer 23

• 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)

Question 24

When cellular PO2 is more than 1 mm Hg, _____ becomes the limiting factor in the rates of chemical change.

Answer 24

•ADP

Question 25

Carbon Dioxide Transport

Answer 25

• 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

Question 26

Bohr vs. Haldane Effects

Answer 26

• 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

Question 27

Carbon Monoxide Transport

Answer 27

• 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**